72. A. Rafalimanana, C. Giordano, A. Ziad, E. Aristidi,
Optimal prediction of atmospheric turbulence by means of WRF model
PASP, accepted (2022)
Abstract :
The performance of ground-based astronomical observations and free space optical communication
(FSOC) system suffers from atmospheric turbulence and meteorological conditions. The a priori knowledge of atmospheric conditions several hours before observations allows to optimize the programming
of astronomical observations (flexible scheduling). In this paper, we present a prediction study based
on the Weather Research and Forecasting (WRF) model. It allows to predict and characterize the
useful set of meteorological parameters relevant to atmospheric physics (e.g. pressure, temperature,
relative humidity, wind speed and direction). Predicted parameters are then injected into an optical
turbulence (OT) model to compute the refractive index structure constant Cn2. We performed sets
of simulations for Cerro Pachon Observatory in Chile, using the data from the National Centers for
Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR). The main goal is
to quantify how accurately numerical weather prediction models can reproduce conditions over the
complex terrain of Cerro Pachon area. In order to produce a reliable forecast, meteorological prognostic skills need accurate representations of the physical parameterization options. Three widely used
Planetary Boundary Layer (PBL) schemes and two Land Surface Model (LSM) were tested, analyzed
and compared in order to find the optimal WRF configuration. Predictions are compared to in-situ
measurements coming from balloon-borne radiosoundings. It is determined that predicted Cn2 are in
good agreement with the radiosoundings measurements with a mean relative error (MRE) under 6.4%
at all altitudes when using balloon measurements to deduce some parameters such as the outer scale of
turbulence L0 which is used in the OT model. For a fully operational prediction, the MREs between
the predictions and the measurements range from 1.4 to 8% according to the different ways to estimate the L0 profiles. Seasonal statistics are also presented for different meteorological and turbulence
parameters.
71. M Ferrais, L. Jorda, P. Vernazza, B. Carry, M. Broz, N. Rambaux, J. Hanus, G. Dudzinski, P. Bartczak, F. Vachier, E. Aristidi, P. Beck, F. Marchis, M. Marsset, M. Viikinkoski, R. Fetick, A. Drouard,
T. Fusco1, M. Birlan, E. Podlewska-Gaca, T. H. Burbine, M. D. Dyar, P. Bendjoya, Z. Benkhaldoun,
J. Berthier, J. Castillo-Rogez, F. Cipriani, F. Colas, C. Dumas, J. Durech, S. Fauvaud, J. Grice, E. Jehin,
†M. Kaasalainen, A. Kryszczynska, P. Lamy, H. Le Coroller, A. Marciniak, T. Michalowski, P. Michel,
J.-L Prieur, V. Reddy, J.-P. Rivet, T. Santana-Ros, M. Scardia, P. Tanga, A. Vigan, O. Witasse, B. Yang
M-type (22) Kalliope: a tiny Mercury
Astron. Astroph., accepted (2022)
Abstract :
We Context. Asteroid (22) Kalliope is the second largest M-type asteroid in the main belt and is orbited by a satellite, Linus. Whereas the mass of
Kalliope is already well constrained thanks to the presence of a moon, its volume is still poorly known, leading to uncertainties on its bulk density
and internal structure.
Aims. We aim at refining the shape of (22) Kalliope and thus its diameter and bulk density, as well as the orbit of its moon to better constrain its
mass, hence density and internal structure.
Methods. We acquired disk-resolved observations of (22) Kalliope using the VLT/SPHERE/ZIMPOL instrument to reconstruct its threedimensional
(3D) shape using three different modeling techniques. These images were also used together with new speckle observations at the
C2PU/PISCO instrument as well as archival images from other large ground-based telescopes to refine the orbit of Linus.
Results. The volume of (22) Kalliope given by the shape models, corresponding to D = 150± 5 km, and the mass constrained by its satellite’s orbit
yield a density of 4.40 ± 0.46 g · cm3. This high density potentially makes (22) Kalliope the densest known small body in the solar system.
A macroporosity in the 10-25% range (as expected for such mass/size), implies a grain density in the 4.8-5.9 g · cm3 range. Kalliope’s high bulk
density, along with its silicate-rich surface implied by its low radar albedo, implies a differentiated interior with metal contributing to most of the
mass of the body.
Conclusions. Kalliope’s high metal content (40-60%) along with its metal-poor mantle makes it the smallest known Mercury-like body. A large
impact at the origin of the formation of the moon Linus is likely the cause of its high metal content and density.
70. R. Gili, J.-L. Prieur, J.-P. Rivet, F. Vakili, M. Scardia, L. Pansecchi, R.W. Argyle, J.F. Ling, L. Piccotti, E. Aristidi, L. Koechlin, D. Bonneau, L. Maccarini, and J. Serot
Measurements of visual binaries with PISCO2 at the Nice 76-cm refractor in 2011-2012
Astron Nacht., 2021
Abstract :
We present relative astrometric and photometric measurements of visual binaries made in 2011-2012, with
PISCO2 installed at the 76-cm refractor of Côte d’Azur Observatory in Nice (France). Our observing list
contains orbital couples as well as binaries whose motion is still uncertain. Three different techniques have
been used for obtaining those measurements: Lucky Imaging, Speckle Interferometry and the Direct Vector
Autocorrelation method. From our observations of 3113 multiple stars, we obtained 3588 new measurements
with angular separations in the range 0".1 - 10" and an average accuracy of 0".016. The mean error on the
position angles is 1°.7. Most of the position angles were determined without the usual 180° ambiguity with
the application of the direct vector autocorrelation technique and/or by inspection of the Lucky images or the
long integration files. We managed to routinely monitor faint systems (V = 9 to 11) with large magnitude
difference (up to delta m=5). We have thus been able to measure many systems containing red dwarf stars
that had been poorly monitored since their discovery. We also measured the magnitude difference of the two
components of 328 binaries with an estimated error of 0.2 mag. Except for a few objects that have been
discussed, our measurements are in a good agreement with the ephemerides computed with published orbital
elements, even for the binaries closer than the diffraction limit. Thanks to good seeing images and with the
use of high-contrast numerical filters, we have also been able to obtain 177 measurements with an angular
separation smaller than the diffraction limit of our instrumentation, and consistent with those obtained with
larger telescopes. We also obtained new measurements of the 15th magnitude multiple system CON37, and
discovered a faint new double star in its vicinity. Finally, we report 42 measurements of 25 new binaries found
during our observations.
69. C. Giordano, A. Rafalimanana, A. Ziad, E. Aristidi, J. Chabé, Y. Fantéï-Caujolle, C. Renaud
Contribution of statistical site learning to improve optical turbulence forecasting
MNRAS, 504, 1927G (2021)
Abstract :
The forecast of the atmospheric and turbulence conditions above astronomical observatories is
of interest for the community because it allows to plan observations with maximum efficiency,
this is called the flexible scheduling. It can also be used to simulate a long term site testing
to give local information useful for the conception of focal and post-focal instrumentation.
We already have presented our forecasting tool in previous publications but in this paper, we
will focus on the importance of using local measurements to improve the predictive turbulence
model and to better consider local specificities of a given site, what we call site learning. For this
study,we used local database provided by the Calern Atmospheric Turbulence Station, installed
since 2015 at the Calern observatory. In addition, a set of several months of predictions to feed
the turbulence model by taking into account daytime and nighttime conditions. This upgrade
improves the quality of our forecasting by reducing the absolute bias between measurements
and predictions from 25 to 50% for each layer of the Cn2, by 25% for the seeing and by 70% for the isoplanatic angle.
68. J. Chabé, E. Aristidi, A. Ziad, H. Lantéri, Y. Fantéï-Caujolle, C. Giordano, J. Borgnino, M. Marjani, C. Renaud
The PML: a generalized monitor of atmospheric turbulence profile with high vertical resolution
Appl. Opt. 59, 7574 (2020)
Abstract :
The future generation of Extremely Large Telescopes will be certainly equipped with Wide-Field Adaptive Optics systems. All the components of such Adaptive Optics systems have to be precisely specified and most of these technical specifications are related to the atmospheric turbulence parameters,
particularly the profile of the refractive index structure constant Cn2(h). The monitor PML (Profiler of Moon Limb) for the extraction of the Cn2(h) profile with high vertical resolution for night-time and daytime conditions by the observation of the Moon limb or Sun edge, has been developed and is now routinely exploited at the Calern Observatory (French Riviera). The PML instrument uses a differential method with two small subapertures mask through which the Moon limb or Sun edge are observed leading to a continuum of double stars allowing a scan of the whole atmosphere with high resolution in
altitude. The PML is an autonomous instrument with the help of a set of equipments such as an allsky camera, a small meteorological station and an automatic system to cover the two subapertures with solar filters to switch from night/Moon to day/Solar observations.In addition, the PML instrument provides in real time a large characterization of the atmospheric turbulence since it is able to measure the other turbulence parameters such as the total seeing and the isoplanatic angle.
67. E. Aristidi, A.Agabi, L. Abe, E. Fossat, A. Ziad, D. Mékarnia
Dome C coherence time statistics from DIMM data
MNRAS 496, 4822 (2020)
Abstract :
We present a reanalysis of several years of DIMM data at the site of Dome C,
Antarctica, to provide measurements of the coherence time tau_0. Statistics
and seasonal behaviour of tau_0 are given at two heights above the ground,
3m and 8m, for the wavelength lambda=500nm. We found an annual median value
of 2.9ms at the height of 8m. A few measurements could also be obtained at
the height of 20m and give a median value of 6ms during the period
June--September. For the first time, we provide measurements of \tau_0 in
daytime during the summer, which appears to show the same time dependence as
the seeing with a sharp maximum at 5pm local time. Exceptional values of
\tau_0 above 10ms are met at this particular moment. The continuous slow
variations of turbulence conditions during the day offers a natural test bed
for a solar adaptive optics system.
66. R. Gili, J.-L. Prieur, J.-P. Rivet, M. Scardia, L. Pansecchi, R.W. Argyle, J.F. Ling, L. Piccotti, E. Aristidi, L. Koechlin, D. Bonneau and L. Maccarini
Measurements of visual binaries with EMCCD cameras and the Nice 76-cm refractor in 2009-2010
Astron. Nacht, 341, 441 (2020)
Abstract :
We present relative astrometric and photometric measurements of visual binaries made in 2009-2010, with the 76-cm refractor of Côte d’Azur Observatory and a pair of sensitive EMCCD ANDOR cameras. Our observing list consists of optical pairs and binaries whose orbital motion is still uncertain. Three different techniques were used for obtaining measurements: Lucky Imaging, Speckle Interferometry and the Direct Vector Autocorrelation method. From the 2050 observations of double stars that we performed, we obtained 1652 new measurements of the relative position of 1792 objects, with angular separations in the range 0.1''— 14''.1. The average accuracy is estimated at 0''.02 for the angular separations and 0.6 degree for the position angles. We managed to observe faint systems (V < 12) with large magnitude difference (up to Δm= 5). We have thus been able to measure many systems containing red dwarf stars that had been poorly monitored since their discovery. We also measured the difference of magnitude of the two components of 1143 objects with an estimated error of 0.2 mag.
65. Quintavalla M., Spagnol M., Abe L., Carbillet M., Aristidi E., Mocci J., Muradore R., Bonora S.
XSAO: an extremely small adaptive optics module for small-aperture telescopes with multiactuator adaptive lens
J. of Astronomical Telescopes, Instruments, and Systems, 6, 029004 (2020)
Abstract :
Although adaptive optics (AO) systems have been developed to compensate for atmospheric turbulence, their application is mostly limited to large size (1.5 to 8 m) telescopes due to high cost and complexity. In particular, for small to medium aperture telescopes for which the need for AO correction is critical, AO systems have different requirements such as compactness and transportability. We report on the realization and the on-sky test of an extremely small adaptive optics module (XSAO) based on a multiactuator adaptive lens. Observations were performed on an 11-in. commercial telescope and a 1-m scientific telescope with minimal modifications. The results show a strong improvement of the acquired images for different types of observed objects, such as bright stars, double stars, planets, and deep sky objects.
64. Scardia M., Rivet J.-P., Prieur J.-L., Pansecchi L., Argyle R. W., Ling J. F., Aristidi E., Zanutta A., Vernet D., Abe L.,
Bendjoya P., Dimur C., Suarez O.
Speckle observations with PISCO in Calern (France): I. Astrometric measurements of visual binaries in 2015–2016
Astron. Nachr., 340, 771 (2019)
Abstract :
We present relative astrometric measurements of visual binaries, made in 2015–2016 with the speckle camera pupil interferometry speckle camera and coronagraph (PISCO) at the 1?m Epsilon telescope of the C2PU facility (Observatoire de la Côte d'Azur, Calern site). Our observing list contains orbital couples as well as binaries whose motion is still uncertain. From our 1233 observations of 1173 multiple stars, we obtained 1170 new measurements with angular separations in the range 0.1-8.2 arcsec, and an average accuracy of 0.0078". The mean error on the position angles is 0.54 degree. Most of the position angles were determined without the usual 180° ambiguity with the application of the direct vector autocorrelation technique and/or by inspection of the long integration files.
63. Ziad A., Aristidi E.,, Chabé J., Borgnino, J.
On the isoplanatic patch size in High Angular Resolution Techniques
MNRAS, 487, 3664 (2019)
Abstract :
To reach a high performance with an Adaptive Optics system, we need a calibration using a reference source. This latter should be located in the same isoplanatic domain as the science source. Different techniques and methods have been developed leading to estimations of the isoplanatic patch but all are model-dependent. We developed a new non model-dependent technique for the estimation of the isoplanatic angle based on an extended object. This technique is now part of our new turbulence profile monitor PML based on the observation of the Moon limb or Sun edge. The first statistics of the isoplanatic angle with this new technique are presented and compared to the exiting techniques based on scintillation measurements or other turbulence parameters such as Fried parameter and/or Cn2 profile.
62. Aristidi E., Ziad A., Chabé J., Fantéi-Caujolle Y., Renaud C., Giordano C.
A generalized differential image motion monitor
MNRAS 486, 915 (2019)
Abstract :
We present a generalized differential image motion monitor (GDIMM). It is a compact instrument dedicated to the measurement of four parameters of optical turbulence: seeing, isoplanatic angle, coherence time and wavefront coherence outer scale. The GDIMM is based on a small telescope (28?cm diameter) equipped with a three-hole mask at its entrance pupil. The instrument is fully automatic, and performs continuous monitoring of turbulence parameters at the Calern Observatory (France). This paper gives a description of the instrument, data processing and error budget. We also present statistics of three and a half years of monitoring of turbulence parameters above the Calern Observatory.
61. Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Zanutta A., Aristidi E..
Speckle observations with PISCO in Merate (Italy): XVI. Astrometric measurements of visual binaries in 2015, and new orbits for DUN 5, ADS 5958, 6276, 7294, 8211 and 13169
Astron. Nacht. 339, 571 (2018)
Abstract :
We present relative astrometric measurements of visual binaries, made in 2015, with the speckle camera PISCO of the 102cm Zeiss telescope of Brera Astronomical Observatory, Merate, Italy. Our observing list contains orbital couples as well as binaries whose motion is still uncertain. We obtained 196 new measurements of 173 visual binary stars, with angular separations in the range 0.27–11.3 arcsec, and an average accuracy of 0.019 arcsec. The mean error on the position angles is 0°.6. Most of the position angles were determined without the usual 180° ambiguity with the application of triple correlation techniques and/or by inspection of the long integration files. We present new revised orbits for DUN 5, ADS 5958, 6276, 7294, 8211, and 13169, partly derived from PISCO observations. The corresponding estimated values for the masses of those systems are compatible with the spectral types. We also computed new rectilinear elements for ADS 4841 for which the physical connection is doubtful from our (and other recent) observations.
60. Carbillet M., Aristidi E., Giordano C., Vernin J.
Anisoplanatic error evaluation and wide-field adaptive optics performance at Dome C, Antarctica
MNRAS 471, 3043C (2017)
Abstract :
The aim of this paper is twofold: (i) to deduce the most representative Cn2 profile(s) for Dome C (DC, Antarctica) from the latest measurements, and (ii) to evaluate the performance of a wide-field adaptive optics (AO) system equipping a 2-3 m telescope. Two models of Cn2 profile, corresponding to the bimodal distribution of seeing (a 'poor seeing' mode and a 'good seeing' mode), are composed from both Single Star Scidar data and balloons radiosoundings. The anisoplanatic error is first evaluated for a standard AO system from Monte-Carlo simulations. DC is shown to outperform Maunakea for both seeing modes. A simple GLAO system is then considered, providing an anisoplanatic error of less than 150 nm over a field of 30 arcmin for the good seeing mode, corresponding to a basic performance Strehl ratio (considering also the fitting and the servo-lag errors) of more than 80% in K and 50% in J. For its part, the poor seeing model shows performances comparable to the MK model. We also studied the influence of the telescope elevation, showing that a telescope at 40 m would perform, in the poor seeing mode, like a telescope observing 8 m above the
ground in the good seeing mode. Finally, we show that while tip-tilt-only correction permits high levels of correction in the good seeing mode at 40 m, it is not as efficient as the GLAO system, even at 8-m altitude, and it is not sufficient for high
levels of correction in the poor seeing case, even at 40-m height.
59. Prieur J.L., Scardia M., Pansecchi L., Argyle R.W., Zanutta A., Aristidi E..
Speckle observations with PISCO in Merate (Italy): XV
Astron. Nacht. 338, 74 (2017)
Abstract :
We present relative astrometric measurements of visual binaries, made in 2013 with the speckle camera PISCO at the 102-cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our observing list contains orbital couples as well as binaries whose motion is still uncertain. We obtained 134 new measurements of 129 visual binary stars, with angular separations in the range 0" .23 - 5" , and an average accuracy of 0".01. The mean error on the position angles is 0.5 deg.. Most of the position angles were determined without the usual 180 deg. ambiguity with the application of triple-correlation techniques and/or by inspection of the
long integration files. We also present new revised orbits for ADS 1097, 5871, 7203, 7775, 9378, 9578 and 11186, partly derived from PISCO observations. The corresponding estimated values for the masses of those systems are compatible with the spectral types.
58. Chapellier E., Mékarnia D., Abe L., Guillot T., Agabi A., Rivet J.-P., Schmider F.-X., Crouzet, N., Aristidi E..
A Catalog of Eclipsing Binaries and Variable Stars Observed with ASTEP 400 from Dome C, Antarctica
ApJS 226, 21 (2016)
Abstract :
We used the large photometric database of the ASTEP program, whose primary goal was to detect exoplanets in the southern hemisphere from Antarctica, to search for eclipsing binaries (EcBs) and variable stars. 673 EcBs and 1166 variable stars were detected, including 31 previously known stars. The resulting online catalogs give the identification, the classification, the period, and the depth or semi-amplitude of each star. Data and light curves for each object are available at http://astep-vo.oca.eu.
57. Mékarnia D., Guillot T., Rivet J.-P., Schmider F.-X., Abe L., Gonçalves I., Agabi A., Crouzet N., Fruth T., Barbieri M., Bayliss D. D. R., Zhou G., Aristidi E., Szulagyi J., Daban J.-B., Fantei-Caujolle Y., Gouvret C., Erikson A., Rauer H., Bouchy F., Gerakis J., Bouchez G.
Transiting planet candidates with ASTEP 400 at Dome C, Antarctica
MNRAS 463, 45 (2016)
Abstract :
ASTEP 400, the main instrument of the ASTEP (Antarctica Search for Transiting ExoPlanets) programme, is a 40-cm telescope, designed to withstand the harsh conditions in Antarctica, achieving a photometric accuracy of a fraction of milli-magnitude on hourly timescales for planet-hosting southern bright (R=12 mag) stars. We review the performances of this instrument, describe its operating conditions, and present results from the analysis of observations obtained during its first three years (2010-2012) of operation, before its repatriation in 2014. During this time, we observed a total of 22 stellar fields (1 degree × 1 degree FoV). Each field, in which we measured stars up to magnitude R=18 mag, was observed continuously during 7 to 30 days. More than 200 000 frames were recorded and 310 000 stars processed, using an implementation of the optimal image subtraction (OIS) photometry algorithm. We found 43 planetary transit candidates. Twenty of these candidates were observed using spectroscopic follow-ups including four targets classified as good planet candidates. Our results demonstrate that accurate near-continuous photometric observations are achievable from the Concordia station at Dome C in Antarctica, even if we were not able to reach the nominal photometric precision of the instrument. We conducted a correlation analysis between the RMS noise and a large number of external parameters and found that source of the 1 mmag correlated noise is not obvious and does not depend on a single parameter. However, our analysis provided some hints and guidance to increase the photometric accuracy of the instrument. These improvements should equip any future telescope operating in Antarctica.
56. Aristidi E., Vernin J., Fossat E., Schmider F.X., Travouillon T., Pouzenc C., Traullé O., Genthon C., Agabi A., Bondoux E., Challita Z., Mékarnia D., Jeanneaux F., Bouchez G.
Monitoring the optical turbulence in the surface layer at Dome C, Antarctica, with sonic anemometers
MNRAS 454, 4304 (2015)
DOI :10.1093/mnras/stv2273
Abstract :
The optical turbulence above Dome C in winter is mainly concentrated in the first tens of meters above the ground. Properties of this so-called surface layer (SL) were investigated during the period 2007-2012 by a set of sonics anemometers placed on a 45 m high tower. We present the results of this long-term monitoring of the refractive index structure constant Cn2 within the SL, and confirm its thickness of 35m. We give statistics of the contribution of the SL to the seeing and coherence time. We also investigate properties of large scale structure functions of the temperature and show evidence of a second inertial zone at kilometric spatial scales.
Abstract :
The installation and operation of a telescope in Antarctica represent particular challenges, in particular the requirement to operate at extremely cold temperatures, to cope with rapid temperature fluctuations and to prevent frosting. Heating of electronic subsystems is a necessity, but solutions must be found to avoid the turbulence induced by temperature fluctuations on the optical paths. ASTEP-400 is a 40 cm Newton telescope installed at the Concordia station, Dome C since 2010 for photometric observations of fields of stars and their exoplanets. While the telescope is designed to spread star light on several pixels to maximize photometric stability, we show that it is nonetheless sensitive to the extreme variations of the seeing at the ground level (between about 0.1 and 5 arcsec) and to temperature fluctuations between -30C and -80C. We analyze both day-time and night-time observations and obtain the magnitude of the seeing caused by the mirrors, dome and camera. The most important effect arises from the heating of the primary mirror which gives rise to a mirror seeing of 0.23 arcsec/K. We propose solutions to mitigate these effects.
54. Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Zanutta A., Aristidi E..
Speckle observations with PISCO in Merate (Italy): XIV. Astrometric measurements of visual binaries in 2013, and new orbits for ADS 1097, 5871, 7203, 7775, 9378, 9578 and 11186
Astron. Nacht. 336, 388 (2015)
Abstract :
We present relative astrometric measurements of visual binaries, made in 2014
with the speckle camera Pupil Interferometry Speckle camera and COronagraph
(PISCO) at the 102-cm Zeiss telescope of Brera Astronomical Observatory, in
Merate. Our observing list contains orbital couples as well as binaries whose
motion is still uncertain. We obtained 224 new measurements of 218 visual binary
stars, with angular separations in the range 0.15?10 arcsec , and an average accuracy
of 0.015 arcsec. The mean error on the position angles is 0.5 degree. Most of the position
angles were determined without the usual 180 degree ambiguity with the application of
triple-correlation techniques and/or by inspection of the long integration files. We
complete this data with the results of a study of the multiple system ADS 6993 with
PISCO during the period 2004?2014 and propose a new method to resolve part
of the 180-degree ambiguity with the autocorrelations only. We then present new
revised orbits for ADS 671, 1615, 1709, 5447, 10075, and 12447, partly derived
from PISCO observations. The corresponding estimated values for the masses of
those systems are compatible with the spectral types.
53. Chadid M., Vernin J., Preston G., Zalian C., Pouzenc C., Abe L., Agabi A., Aristidi E., Liu L.Y., Mékarnia D., Trinquet H.
First detection of multi-shocks in RR Lyrae stars from Antarctica: a possible explanation of the blazhko effect
The Astron. Journal 148, 88 (2014)
Abstract :
We present the first detection of multi-shocks propagating through the atmosphere of the Blazhko star S Arae using uninterrupted, accurate optical photometric data collected during one polar night, 150 days from Antarctica at Dome C, with the Photometer AntarctIca eXtinction (PAIX). We acquired 89,736 CCD frames during 323 pulsation cycles and 3 Blazhko cycles. We detected two new light curve properties in the PAIX light curve, jump and rump, which we associated with two new post-maximum shock waves ShPM1 and ShPM2. jump, lump, rump, bump, and hump are induced by five shock waves, with different amplitudes and origins, ShPM1, ShPM, ShPM2, ShPM3, and the main shock ShH + He. Correlations between the length of rise time and light amplitude and ShPM3 are monotonous during three Blazhko cycles, but the pulsation curve is double peaked. We discuss the physical mechanisms driving the modulation of these quantities. Finally, we hypothesize that the origin of the Blazhko effect is a dynamical interaction between a multi-shock structure and an outflowing wind in a coronal structure.
52. Prieur J.L., Scardia M., Pansecchi L., Argyle B., Zanutta A., Aristidi E.
Speckle observations with PISCO in Merate:
XIII. Astrometric measurements of visual binaries in 2012, and new orbits for ADS 10786 BC, 12144, 12515, 16314 and 16539
Astron. Nachr. 335, 817 (2014)
Abstract :
We present relative astrometric measurements of visual binaries, made in 2012 with the speckle camera PISCO at the
102-cm Zeiss telescope of Brera Astronomical Observatory, in Merate. Our observing list contains orbital couples as well
as binaries whose motion is still uncertain. We obtained 355 new measurements of 344 visual binary stars, with angular
separations in the range 0.14 - 6.9 arcsec, and an average accuracy of 0.02 arcsec. The mean error on the position angles is 0.05 degree. Most of the position angles were determined without the usual 180 degree ambiguity with the application of triple-correlation techniques and/or by inspection of the long integration files. We also present new revised orbits for ADS 10786 BC, 12144, 12515, 16314, and 16539, partly derived from PISCO observations. The corresponding estimated values for the masses of those systems are compatible with the spectral types.
51. Petenko I., Argentini S., Pietroni I., Viola A., Mastrantonio G., Casasanta G.,
Aristidi E., Bouchez G., Agabi A., Bondoux E.
Qualitative observations of the optically-active turbulence in the planetary boundary layer by sodar at Concordia astronomical observatory, Dome C, Antarctica
A&A 568, 44 (2014)
Abstract :
Aims. During the winter-over campaign carried out at the Concordia station in Antarctica in 2012, an experiment to determine the behaviour of optically-active atmospheric turbulence in the lower part of the atmospheric boundary layer and its influence on the quality of astronomical images. This place is characterised by high quality of astronomical images (low seeing values). The surface layer in the interior of Antarctica during winter is extremely stably stratified with the difference of temperature between the surface and the top of the inversion reaching 20-35C. In spite of such strong static stability, the considerable thermal optically-active turbulence occurs sometimes and extends up to several tens of metres depending on weather conditions. It is important to know the meteorological characteristics favouring good astronomical observations.
Methods. The optical measurements of the seeing (made by differential image motion monitors (DIMM) installed at 2 levels: 8 and 20 m) were accompanied by observations of the turbulence in the lowest hundred meters of the atmosphere. The thermal optically-active turbulence was detected and evaluated using a specially designed high-resolution sodar. Also, the statistics of some relevant meteorological variables including long-wave downward radiation characterising the presence of cloudiness were determined.
Results. Typical patterns of the spatial and temporal structure of turbulence shown by sodar echograms were analysed and classified. Statistics of the depth of surface-based turbulent layer as well as of the turbulent optical factor over different height layers are presented together with the statistics of seeing values. Dependence of the seeing and the integral intensity of turbulence within the first 100 m on temperature and wind speed was analyzed.
Conclusions. The clear correlation seems to exist between the seeing values and the intensity of turbulence in the atmospheric boundary layer. The best values of the seeing < 1arcsec are observed when sodar shows very low turbulence intensity. The presented statistics of the vertical distribution of the optically-active turbulence can be used when determining the optimal allocation of astronomical instruments. The main contribution to the image distortion is due to turbulence generated within the lowest 30 - 50 m near the surface.
50. Ziad A., Blary F., Borgnino J.,
Fantei-Caujolle Y., Aristidi E., Martin F., Lanteri H., Douet R.,
Bondoux E., Mekarnia D.
First results of the PML monitor of atmospheric turbulence profile with high vertical resolution A&A, 559, L6 (2013)
Abstract
:
Aims. Future Extremely Large Telescopes will be certainly equipped with
Wide-Field Adaptive Optics systems. The optimization of
the performances of these techniques requires a precise specification
of the different components of these AO systems. Most of these
technical specifications are related to the atmospheric turbulence
parameters, particularly the profile of the refractive index structure
constant CN2(h). A new monitor PML (Profiler of Moon Limb) for the
extraction of the CN2(h) profile with high vertical resolution and
its first results are presented.
Methods. The PML instrument uses an optical method based on the observation of the Moon limb through two subapertures. The use
of the lunar limb leads to a continuum of double stars allowing a scan of the whole atmosphere with high resolution in altitude.
Results. The first prototype of the PML has been installed at Dome C in
Antarctica and the first results of the PML are presented
and compared to radio-sounding balloon profiles. In addition of the
CN2(h) profile obtained with high vertical resolution, PML is also
able to provide the other atmospheric turbulence parameters as the
outer scale profile, the total seeing, the isoplanatic and isopistonic
angles.
Abstract
:
One year field experiment has started on December 2011 at the French - Italian station of Concordia at Dome C, East Antarctic Plateau. The objective of the experiment is the study of the surface layer turbulent processes under stable/very stable stratifications, and the mechanisms leading to the formation of the warming events. A sodar was improved to achieve the vertical/time resolution needed to study these processes. The system, named Surface Layer sodar (SL-sodar), may operate both in high vertical resolution (low range) and low vertical resolution (high range) modes. In situ turbulence and radiation measurements were also provided in the framework of this experiment. A few preliminary results, concerning the standard summer diurnal cycle, a summer warming event, and unusually high frequency boundary layer atmospheric gravity waves are presented.
48. Giordano C., Vernin J., Chadid M., Aristidi E.,
Agabi A., Trinquet H.,
Dome C site
characterisation in 2006 with Single Star Scidar PASP, 124, 494 (2012)
Abstract
:
We present observations made in 2006 with the single-star SCIDAR (SSS)
at Dome C in Antarctica, allowing us to determine optical turbulence
C2N(h) and velocity V(h) profiles from ice levels
up to about 25 km above sea level (a.s.l.). SSS is a 16 inch telescope
placed on an equatorial mount that continuously tracks the Canopus
star.
About 90,000 individual profiles are analyzed from March to September,
where surface-layer contribution to seeing can be separated from the
rest of the atmosphere. Medians of high angular resolution parameters
relevant to astronomy are statistically studied, such as seeing (1.0"),
isoplanatic angle (6.9"), and wavefront coherence time (3.4 ms). For a
telescope placed above the turbulent surface layer, superb conditions
are encountered (medians of seeing better than 0.3", isoplanatic angle
better than 6.9", and coherence time larger than 10 ms). Astronomical
conditions are twice as good at the beginning of the night, with
ɛ0 ≈ 0.5", θ0 ≈ 11.5", and
τ0 ≈ 15 ms. SSS wind-velocity profiles are consistent
with National Oceanic and Atmospheric Administration analysis up to 17
km (a.s.l.), within a ±2 m/s error bar. Coherence étendue (which is a
combination of ɛ0, θ0, and
τ0), well adapted to adaptive optics performances, is
likely 4 times better at Dome C than at the already-known observatories
such as Mauna Kea or ORM.
Abstract
:
Context: The winter seeing at Concordia is essentially bimodal,
excellent or
quite poor, with relative proportions that depend on altitude above the
snow
surface. This paper studies the temporal behavior of the good seeing
sequences.
Aims: An efficient
exploitation of extremely good seeing with an adaptive
optics system needs long integrations. It is then important to explore
the
temporal distribution of the fraction of time providing excellent
seeing.
Methods: Temporal windows of good
seeing are created by a simple binary
process. Good or bad. Their autocorrelations are corrected for those of
the
existing data sets, since these are not continuous, being often
interrupted by
technical problems in addition to the adverse weather gaps. At the end
these
corrected autocorrelations provide the typical duration of good seeing
sequences. This study has to be a little detailed as its results depend
on the
season, summer or winter.
Results: Using a threshold of 0.5
arcsec to define
the "good seeing", three characteristic numbers are found to describe
the
temporal evolution of the good seeing windows. The first number is the
mean
duration of an uninterrupted good seeing sequence: it is tau_0=7.5
hours at
8 m above the ground (15 hours at 20 m). These sequences are randomly
distributed in time, with a negative exponential law of damping time
tau_1=29 hours (at elevation 8 m and 20 m). The third number is the
mean
time between two 29 hours episodes. It is T=10 days at 8 m high (5 days
at 20
m).
Abstract
:
This paper analyses 3 1/2 years of site testing data obtained at Dome
C, Antarctica, based on measurements obtained with three DIMMs located
at three different elevations. Basic statistics of the seeing and the
isoplanatic angle are given, as well as the characteristic time of
temporal fluctuations of these two parameters, which we found to around
30 min at 8 m. The 3 DIMMs are exploited as a profiler of the surface
layer, and provide a robust estimation of its statistical properties.
It appears to have a very sharp upper limit (less than 1 m). The
fraction of time spent by each telescope above the top of the surface
layer permits us to deduce a median height of between 23 m and 27 m.
The comparison of the different data sets led us to infer the
statistical properties of the free atmosphere seeing, with a median
value of 0.36 arcsec. The C_n2 profile inside the surface
layer is also deduced from the seeing data obtained during the fraction
of time spent by the 3 telescopes inside this turbulence.
Statistically, the surface layer, except during the 3-month summer
season, contributes to 95 percent of the total turbulence from the
surface level, thus confirming the exceptional quality of the site
above it.
45. Guerri G., Abe L., Daban J.B., Aristidi E.,
Bendjoya P. Rivet J.P., Vakili F.
Progress
report on phase knife stellar coronograph at Dome C Antarctic Science, 21, 533
(2009)
Abstract
:
We report on preliminary on-sky tests of a phase knife stellar
coronagraph operated in the
visible from the French-Italian Concordia station at Dome C of
Antarctica. Laboratory
experiments and numerical simulation results are also presented, and
the experimental
feedback for further observation campaigns is discussed.
Abstract
:
Context: For detecting and directly imaging exoplanets, coronagraphic
methods are mandatory when the intensity ratio between a star and its
orbiting planet can be as large as 10^6. In 1996, a concept of an
achromatic interfero-coronagraph (AIC) was presented for detecting very
faint stellar companions, such as exoplanets.
Aims: We present a
modified version of the AIC not only permitting these faint companions
to be detected but also their relative position to be determined with
respect to the parent star, a problem that was not solved in the
original design of the AIC.
Methods: In our modified design,
two
cylindrical lens doublets were used to remove the 180° ambiguity
introduced by the AIC's original design.
Results: Our theoretical
study and the numerical computations show that the axis of symmetry is
destroyed when one of the cylindrical doublets is rotated around the
optical axis
43 Vernin J.; Chadid M.; Aristidi
E.; Agabi A.; Trinquet H.; Van der Swaelmen M.
First
Single Star Scidar measurements at Dome C, Antarctica A&A, 500, 1271 (2009)
Abstract
:
Aims: We investigate the first operational running of the Single Star
Scidar (SSS instrument) under harsh weather conditions at Dome C in
Antarctica and examine continuous monitoring of the optical turbulence
and wind speed profiles throughout the atmosphere.
Methods: SSS
is mainly composed of commercially available light-weight components
and
a 16 inch telescope installed on an equatorial mount. Scintillation
patterns were computed (auto and cross-correlations) in real time and
analyzed off line to retrieve continuously vertical profiles of optical
turbulence C_N^2(h) and wind speed V(h), from the ground up to 20 km.
Results: Using a simulated
annealing method, we have analyzed
about 6.5 h of observations, revealing the strong surface layer
contribution to seeing degradation. SSS results show a good seeing
agreement with simultaneous measurements with a Differential Image
Motion Monitor, even under very good seeing as low as 0.2 arcsec, as
well as wind speed agreement when compared to the weather archive from
NOAA.
Conclusions: SSS has shown its
usefulness for site
characterization since it simultaneously measures C_N2 and V
profiles, from which most adaptative optic parameters are deduced, such
as isoplanatic angle and coherence time of the wavefront. Due to its
small size, it is well adapted for site characterization, even when low
infrastructure is available.
42. Ziad A.,
Aristidi E., Agabi A., Borgnino
J., Martin F., Fossat E.
First
statistics of turbulence outer scale at Dome C A&A, 491, 917 (2008)
Abstract
:
Context. The outer scale of wavefronts is of interest for the
dimensioning and the optimisation of the High Angular Resolution
techniques (HAR) such Interferometry and Adaptive Optics particularly
for the new telescope generation as Extremely Large Telescopes
(ELT).
Aims. Providing the first
statistics of the outer scale at Dome C site to finalize the characterization of this site. Methods. A new
version of the Generalized Seeing Monitor has been developed for
extreme cold conditions. Indeed, two DIMMs have been coupled to extract
Angle-of-Arrival (AA) fluctuations using CCD detectors. Correlations
of these AA fluctuations for different baselines lead to outer scale
estimations.
Results. For the first time,
statistics of the outer scale at Dome C are provided leading to small
values comparatively to temperate sites reducing considerably the
fringe excursion of interferometers and the low orders of the Zernike
modes particularly the tip-tilt.
Conclusions. The Dome C small
outer scale combined to the large coherence time and large isoplanatic
angle are very beneficial for the development of Adaptive Optique
systems and long-baseline interferometers.
41. Prieur, J.-L.;
Scardia, M.;
Pansecchi, L.; Argyle, R. W.; Sala, M.;
Ghigo, M.; Koechlin, L.; Aristidi, E.
SPECKLE
OBSERVATIONS WITH PISCO IN MERATE: V. ASTROMETRIC MEASUREMENTS OF
VISUAL BINARIES IN 2006 MNRAS, 387 772 (2008)
Abstract
:
We present relative astrometric measurements of visual binaries made
during the first semester of 2006, with the Pupil Interferometry
Speckle camera and COronagraph at the 102-cm Zeiss telescope of the
Brera Astronomical Observatory, in Merate. Our sample contains orbital
couples as well as binaries whose motion is still uncertain. We
obtained 217 new measurements of 194 objects, with angular separations
in the range 0.1-4.2arcsec, and an average accuracy of 0.01arcsec. The
mean error on the position angles is 0.5 deg.. About half of those
angles could be determined without the usual 180 deg. ambiguity by the
application of triple-correlation techniques. We also present a revised
orbit for ADS 277 for which the previously published orbit resulted in
a large residual from our measurements.
40. Trinquet, H; Agabi, A; Vernin, J;
Azouit, M; Aristidi, E; Fossat, E
NIGHTTIME
OPTICAL TURBULENCE VERTICAL STRUCTURE ABOVE DOME C IN ANTARCTICA PASP, 120, 203 (2008)
Abstract
:
During the austral winter 2005, the first astronomical site testing
campaign were performed at Dome C, in Antarctica. Thirty-five
meteorological balloons equipped with microthermal sensors were used to
sense the vertical profile of the optical turbulence intensity C N 2
profiles of midlatitude sites. Of the whole optical turbulence, 80%
lies within the first 33m above the ground and 9% in the upper part of
the boundary layer, between 33m and 1km above the ground. The remaining
11% are in the free atmosphere. This is an extreme situation when
compared with classical midlatitude sites where the surface layer
extends up to 200m. This strong and thin surface layer is the result of
the kinetic turbulent mixing of air combined with a strong potential
temperature gradient. The site is characterized from the adaptive
optics point of view. Seeing, isoplanatic angle, and coherence time are
estimated for each considered seasons. A four-layer decomposition for
each season is provided for adaptive optics simulations. For high
angular astronomy, a telescope at Dome C needs to be elevated over this
surface layer, or a specific GLAO needs to be designed. Combined with
the unique possibility of performing continuous observation from
Antarctica, scientific programs such as microlensing, pulsating stars,
and asteroseismology become feasible.
39. Scardia, M.; Prieur, J.-L.;
Pansecchi, L.; Argyle, R. W.; Sala, M.;
Basso, S.; Ghigo, M.; Koechlin, L.; Aristidi, E.
SPECKLE
OBSERVATIONS WITH PISCO IN MERATE: IV. ASTROMETRIC MEASUREMENTS OF
VISUAL BINARIES IN 2005 AN, 329 54 (2008)
Abstract
:
We present relative astrometric measurements of visual binaries made
during the second semester of 2005, with the speckle camera PISCO at
the 102 cm Zeiss telescope of Brera Astronomical Observatory, in
Merate. Our sample contains orbital couples as well as binaries whose
motion is still uncertain. The purpose of this long term program is to
improve the accuracy of the orbits and determine the masses of the
components. We performed 130 new observations of 120 objects, with most
of the angular separations in the range 0"1-4", and with an average
accuracy of 0"01. Most of the position angles could be determined
without the usual 180 deg. ambiguity with the application of
triple-correlation techniques, and their mean error is 0\fdg8. We have
found a possible new triple system: ADS 11077. Å¡kip0.15cm The
measurements of the closest binaries were made with a new data
reduction procedure, based on model fitting of the background of the
auto-correlations. As this procedure proved to be very efficient, we
have re-processed the old observations of close binaries made with
PISCO in Merate since 2004. We thus improved 20 measurements already
published and obtained 7 new measurements for observations that were
previously reported as ``unresolved".\ We finally present revised
orbits for ADS 684, MCA 55Aac (in the Beta 1 Cyg-Albireo multiple
system) and ADS 14783 for which the previously published orbits led to
large residuals with our measurements and for which the new
observations made since their computation allowed a significant
improvement of those old orbits. The sum of the masses that we derived
for those systems are consistent with the spectral type of the stars
and the dynamic parallaxes are in good agreement with the parallaxes
measured by Hipparcos.
Abstract
:
We report the observations of the clear-sky fraction at the
Concordia station during winter 2006 and derive from it the duty cycle
for the astronomical observations. The duty cycle and observation
duration at Dome C allow for efficient asteroseismic observations. This
performance is analyzed and compared to network observations. For
network observations, simulations were run using the helioseismic
Global Oscillation Network Group as a reference. Observations with one
site in Antarctica provide performance similar to or better than that
with a six-site network, since the duty cycle limited by meteorology is
as high as 92%. On bright targets, a 100 day long time series with a
duty cycle of about 87% can be observed, which is not possible for a
network observation.
Based on observations made by E.
Aristidi during the 2006 second overwinter at the French-Italian
Concordia Station, Dome C, Antarctica.
37. Millour, F.;
Petrov, R. G.; Chesneau, O.; Bonneau, D., et al.
(AMBER collaboration)
DIRECT
CONCTRAINT ON THE DISTANCE OF GAMMA2 VELORUM FROM AMBER/VLTI
OBSERVATIONS Astron. Astroph.,
464, 107 (2007)
Abstract
:
Context: Interferometry can provide spatially
resolved observations of massive star binary systems and their
colliding winds, which thus far have been studied mostly with
spatially unresolved observations. Aims:
We present the first
AMBER/VLTI observations, taken at orbital phase 0.32, of the
Wolf-Rayet and O (WR+O) star binary system Gamma2 Velorum and use the
interferometric observables to constrain its properties. Methods: The
AMBER/VLTI instrument was used with the telescopes UT2, UT3, and UT4
on baselines ranging from 46 m to 85 m. It delivered spectrally
dispersed visibilities, as well as differential and closure phases,
with a resolution R=1500 in the spectral band 1.95-2.17 μm. We
interpret these data in the context of a binary system with
unresolved components, neglecting in a first approximation the
wind-wind collision zone flux contribution. Results: Using WR- and
O-star synthetic spectra, we show that the AMBER/VLTI observables
result primarily from the contribution of the individual components
of the WR+O binary system. We discuss several interpretations of the
residuals, and speculate on the detection of an additional continuum
component, originating from the free-free emission associated with
the wind-wind collision zone (WWCZ), and contributing at most to the
observed K-band flux at the 5% level. Based on the accurate
spectroscopic orbit and the Hipparcos distance, the expected absolute
separation and position angle at the time of observations were
5.1±0.9 mas and 66±15 deg., respectively. However, using theoretical
estimates for the spatial extent of both continuum and line emission
from each component, we infer a separation of 3.62+0.11-0.30
mas and a position angle of 73+9-11 deg.,
compatible with the expected one. Our analysis thus implies that the
binary system lies at a distance of 368+38-13
pc, in agreement with recent spectrophotometric estimates, but
significantly larger than the Hipparcos value of 258+41-31
pc.
36. Weigelt, G.; Kraus, S.; Driebe, T.;
Petrov, R. G.; ., et al. (AMBER collaboration)
NEAR INFRARED INTERFEROMETRY OF ETA CARINAE WITH
SPECTRAL RESOLUTIONS 1500 AND 12000 USING AMBER/VLTI Astron. Astroph., 464, 87 (2007)
Abstract :
Aims. We present
the first NIR spectro-interferometry of the LBV Eta Carinae. The
observations were performed with the AMBER instrument of the ESO Very
Large Telescope Interferometer (VLTI) using baselines from 42 to 89
m. The aim of this work is to study the wavelength dependence of η
Car's optically thick wind region with a high spatial resolution of 5
mas (11 AU) and high spectral resolution. Methods: The observations
were carried out with three 8.2 m Unit Telescopes in the K-band. The
raw data are spectrally dispersed interferograms obtained with
spectral resolutions of 1500 (MR-K mode) and 12 000 (HR-K mode). The
MR-K observations were performed in the wavelength range around both
the He I 2.059 μm and the Brγ 2.166 μm emission lines, the HR-K
observations only in the Brγ line region. Results: The spectrally
dispersed AMBER interferograms allow the investigation of the
wavelength dependence of the visibility, differential phase, and
closure phase of Eta Car. In the K-band continuum, a diameter of
4.0±0.2 mas (Gaussian FWHM, fit range 28-89 m baseline length) was
measured for η Car's optically thick wind region. If we fit Hillier
et al. (2001, ApJ, 553, 837) model visibilities to the observed AMBER
visibilities, we obtain 50% encircled-energy diameters of 4.2, 6.5
and 9.6 mas in the 2.17 μm continuum, the He I, and the Brγ
emission lines, respectively. In the continuum near the Brγ line, an
elongation along a position angle of 120 deg.±15 deg. was found,
consistent with previous VINCI/VLTI measurements by van Boekel et al.
(2003, A&A, 410, L37). We compare the measured visibilities with
predictions of the radiative transfer model of Hillier et al. (2001),
finding good agreement. Furthermore, we discuss the detectability of
the hypothetical hot binary companion. For the interpretation of the
non-zero differential and closure phases measured within the Brγ
line, we present a simple geometric model of an inclined,
latitude-dependent wind zone. Our observations support theoretical
models of anisotropic winds from fast-rotating, luminous hot stars
with enhanced high-velocity mass loss near the polar regions.
Abstract :
We
study the geometry and kinematics of the circumstellar environment of
the Be star kappa CMa in the Br-gamma emission line and its nearby
continuum. Methods: We use the AMBER/VLTI instrument operating in the
K band, which provides a spatial resolution of about 6 mas with a
spectral resolution of 1500, to study the kinematics within the disk
and to infer its rotation law. To obtain more kinematical constraints
we also use a high spectral resolution Paβ line profile obtain in
December 2005 at the Observatorio do Pico do Dios, Brazil and we
compile V/R line profile variations and spectral energy distribution
data points from the literature. Results: Using differential
visibilities and differential phases across the Brγ line we detect
an asymmetry in the disk. Moreover, we found that κ CMa seems
difficult to fit within the classical scenario for Be stars,
illustrated recently by α Arae observations, i.e. a fast rotating B
star close to its breakup velocity surrounded by a Keplerian
circumstellar disk with an enhanced polar wind. We discuss the
possibility that kappa CMa is a critical rotator with a Keplerian
rotating disk and examine whether if the detected asymmetry can be
interpreted within the "one-armed" viscous disk framework.
Abstract
:
Aims.We investigate the origin of the Brγ emission
of the Herbig Ae star HD 104237 on Astronomical Unit (AU) scales.
Methods: Using AMBER/VLTI at a spectral resolution R=1500 we
spatially resolve the emission in both the Brγ line and the adjacent
continuum. Results: The visibility does not vary between the
continuum and the Brγ line, even though the line is strongly
detected in the spectrum, with a peak intensity 35% above the
continuum. This demonstrates that the line and continuum emission
have similar size scales. We assume that the K-band continuum excess
originates in a "puffed-up" inner rim of the circumstellar disk,
and discuss the likely origin of Br-gamma. Conclusions: .We conclude that
this emission most likely arises from a compact disk wind, launched
from a region 0.2-0.5 AU from the star, with a spatial extent similar
to that of the near infrared continuum emission region, i.e., very
close to the inner rim location.
33. Malbet F., Benisty M., De Wit
W.J., et al. (AMBER collaboration)
DISK AND WIND INTERACTION IN THE YOUNG STELLAR
OBJECT MWC 297 SPATIALLY RESOLVED WITH AMBER/VLTI Astron.
Astroph., 464, 43 (2007)
Abstract
:
The young stellar object MWC 297 has been observed
with the VLT interferometer equipped with the AMBER instrument. MWC
297 has been spatially resolved in the continuum with a visibility of
0.50 as well as in the Br gamma emission line where the visibility
decrease to a lower value of 0.33. This change in the visibility with
the wavelength can be interpreted by the presence of an optically
thick disk responsible for the visibility in the continuum and of a
stellar wind traced by Br gamma and whose apparent size is 40%
larger. We validate this interpretation by building a model of the
stellar environment that combines a geometrically thin, optically
thick accretion disk model consisting of gas and dust, and a
latitude-dependent stellar wind outflowing above the disk surface.
The continuum emission and visibilities obtained from this model are
fully consistent with the interferometric AMBER data. They agree also
with existing optical, near-infrared spectra and other broad-band
near-infrared interferometric visibilities. A picture emerges in
which MWC 297 is surrounded by an equatorial flat disk that is
possibly still accreting and an outflowing wind which has a much
higher velocity in the polar region than at the equator.
32. Tatulli E., Millour F., Chelli F., et al. (AMBER
collaboration)
INTERFEROMETRIC DATA REDUCTION WITH AMBER/VLTI.
PRINCIPLE, ESTIMATORS AND ILLUSTRATION Astron. Astroph., 464, 29 (2007)
Bibliographic Code :2007A&A...464...29T
Abstract :
Aims.In this paper,
we present an innovative data reduction method for single-mode
interferometry. It has been specifically developed for the AMBER
instrument, the three-beam combiner of the Very Large Telescope
Interferometer, but it can be derived for any single-mode
interferometer. Methods: The algorithm is based on a direct modelling
of the fringes in the detector plane. As such, it requires a
preliminary calibration of the instrument in order to obtain the
calibration matrix that builds the linear relationship between the
interferogram and the interferometric observable, which is the
complex visibility. Once the calibration procedure has been
performed, the signal processing appears to be a classical
least-square determination of a linear inverse problem. From the
estimated complex visibility, we derive the squared visibility, the
closure phase, and the spectral differential phase. Results: The data
reduction procedures have been gathered into the so-called amdlib
software, now available for the community, and are presented in this
paper. Furthermore, each step in this original algorithm is
illustrated and discussed from various on-sky observations conducted
with the VLTI, with a focus on the control of the data quality and
the effective execution of the data reduction procedures. We point
out the present limited performances of the instrument due to VLTI
instrumental vibrations which are difficult to calibrate.
31. Robbe-Dubois S., Lagarde S. Petrov R., et al. (AMBER
collaboration)
OPTICAL CONFIGURATION AND ANALYSIS OF THE AMBER/VLTI
INSTRUMENT Astron. Astroph., 464, 13 (2007)
Abstract :
Aims.This paper
describes the design goals and engineering efforts that led to the
realization of AMBER (Astronomical Multi BEam combineR) and to the
achievement of its present performance. Methods: On the basis of the
general instrumental concept, AMBER was decomposed into modules whose
functions and detailed characteristics are given. Emphasis is put on
the spatial filtering system, a key element of the instrument. We
established a budget for transmission and contrast degradation
through the different modules, and made the detailed optical design.
The latter confirmed the overall performance of the instrument and
defined the exact implementation of the AMBER optics. Results: The
performance was assessed with laboratory measurements and
commissionings at the VLTI, in terms of spectral coverage and
resolution, instrumental contrast higher than 0.80, minimum magnitude
of 11 in K, absolute visibility accuracy of 1%, and differential
phase stability of 10-3 rad over one minute.
30. Petrov R., Malbet F., Weigelt, et al. (AMBER collaboration)
AMBER, THE
NEAR INFRARED SPECTRO INTERFEROMETRIC THREE TELESCOPE VLTI INSTRUMENT Astron. Astroph., 464, 1 (2007)
Abstract
:
Context: Optical long-baseline interferometry is moving a crucial step
forward with the advent of general-user scientific instruments that
equip large aperture and hectometric baseline facilities, such as the
Very Large Telescope Interferometer (VLTI). Aims: AMBER is one of the
VLTI instruments that combines up to three beams with low, moderate and
high spectral resolutions in order to provide milli-arcsecond spatial
resolution for compact astrophysical sources in the near-infrared
wavelength domain. Its main specifications are based on three key
programs on young stellar objects, active galactic nuclei central
regions, masses, and spectra of hot extra-solar planets. Methods: These
key science goals led to scientific specifications, which were used to
propose and then validate the instrument concept. AMBER uses
single-mode fibers to filter the entrance signal and to reach highly
accurate, multiaxial three-beam combination, yielding three baselines
and a closure phase, three spectral dispersive elements, and specific
self-calibration procedures. Results: The AMBER measurements yield
spectrally dispersed calibrated visibilities, color-differential
complex visibilities, and a closure phase allows astronomers to
contemplate rudimentary imaging and highly accurate visibility and
phase differential measurements. AMBER was installed in 2004 at the
Paranal Observatory. We describe here the present implementation of the
instrument in the configuration with which the astronomical community
can access it. Conclusions: .After two years of commissioning tests and
preliminary observations, AMBER has produced its first refereed
publications, allowing assessment of its scientific potential.
29. Sadibekova T., Fossat E., Genthon C., Krinner G.,
Aristidi E., Agabi K., Azouit M
ON THE ATMOSPHERE FOR ASTRONOMERS ABOVE DOME C,
ANTARCTICA Antarctic Science, 18, 437
(2006)
Abstract :
This paper
describes a comparison between balloon radio-soundings made in summer
at the Concordia station, Dome C, Antarctica and coincident
model-based meteorological analyses. The comparison allows the
assessment of the reliability of the analyses in summer. This allows
the use of the winter analyses within an estimated range of
uncertainty, while the first in situ measurements are just becoming
available. The astronomical interest is to produce an estimate of
atmospheric turbulence during the Antarctic winter at this very
promising site. For this work the 6-hourly ECMWF operational analyses
were used, concurrently with the data obtained in situ by the
radio-sounding made at Concordia with standard meteorological
balloons and sondes during four summer seasons (November-January),
from December 2000 to the end of January 2004.
28. Scardia M., Prieur J.-L., Pansecchi L.,
Argyle R. W., Basso S., Sala M., Ghigo M.,
Koechlin L., B. Aristidi E.
SPECKLE OBSERVATIONS WITH PISCO AT MERATE - III.
ASTROMETRIC MEASUREMENTS OF VISUAL BINARIES IN 2005 AND SCALE
CALIBRATION WITH A GRATING MASK MNRAS, 374, 965 (2007)
Abstract :
We present
relative astrometric measurements of visual binaries made during the
first semester of 2005, with the Pupil Interferometry Speckle Camera
and Coronagraph (PISCO) at the 102-cm Zeiss telescope of the Brera
Astronomical Observatory, in Merate. We performed 214 new
observations of 192 objects, with angular separations in the range
0.2-4.3arcsec, and with an average accuracy of 0.01arcsec. Most of
the position angles could be determined without the usual 180 deg.
ambiguity, and their mean error is . Our sample contains orbital
couples as well as binaries whose motion is still uncertain. The
purpose of this long-term programme is to improve the accuracy of the
orbits and constrain the masses of the components.
For the first time with PISCO, the
astrometric calibration was made with a grating mask mounted at the
entrance of the telescope. The advantage of this procedure is to
provide a reliable and fully independent scale determination.
We have found two possible new triple
systems: ADS 7871 and KUI 15. We propose a preliminary orbit for ADS
4208
27. Agabi A., Aristidi E., Azouit M., Fossat E., Martin F.,
Sadibekova T., Vernin J., Ziad A.
FIRST WHOLE ATMOSPHERE NIGHT TIME SEEING MEASUREMENTS
AT DOME C, ANTARCTICA PASP, 118, 344 (2006)
Abstract :
We report site
testing results obtained in night-time during the polar autumn and
winter at Dome C. These results were collected during the first
Concordia winterover by A. Agabi. They are based upon seeing and
isoplanatic angle monitoring, as well as in-situ balloon measurements
of the refractive index structure constant profiles C_n^2(h).
Atmosphere is divided into two regions: (i) a 36 m high surface
layer responsible of 87% of the turbulence and (ii) a very stable
free atmosphere above with a median seeing of 0.36+-0.19 arcsec at an
elevation of h=30m. The median seeing measured with a DIMM placed on
top of a 8.5m high tower is 1.3+-0.8 arcsec.
Abstract :
We present relative
astrometric measurements of visual binaries taken during the
second semester of 2004 with the Pupil Interferometry Speckle camera
and Coronagraph (PISCO) at the 1-m Zeiss telescope of the Brera
Astronomical Observatory, in Merate, Italy. We performed 207 new
observations of 194 objects with angular separations in the range
0.1-4.0 arcsec and an accuracy better than ~0.01 arcsec. Our sample
contains orbital couples as well as binaries whose motion is still
uncertain. Our purpose is to improve the accuracy of the orbits and
constrain the masses of the components.
Those measurements show that the orbit
of ADS 15115 needs to be revised; we propose a new orbit for this
object.
25. Kellerer A., Sarazin M.,
Coudé Du Foresto V., Agabi K., Aristidi E.,
Sadibekova T.
METHOD OF ESTIMATING TIME SCALES OF THE ATMOSPHERIC
PISTON AND ITS APPLICATION AT DOME C (ANTARCTICA) App. Opt., 45, 5709
(2006)
Abstract :
Analysis of the
first interferometric fringes recorded at Dome C, Antarctica are
presented. Measurements were taken 31 January and 1 February 2005
during daytime. Our purpose in performing the analysis was to measure
temporal fluctuations of the atmospheric piston, which are critical
for interferometers, and determine their sensitivity. These scales
are derived through the motion of the image that is formed in the
focal plane of a Fizeau interferometer. We could establish a lower
limit to the coherence time by studying the decay rate of correlation
between successive fringes. Coherence times are measured to be larger
than 10 ms, i.e., at least three times higher than the median
coherence time measured at the site of Paranal (3.3 ms).
24. E. Aristidi, A. Agabi, E. Fossat, Azouit M., Martin F.,
Sadibekova T., Travouillon T., Vernin J., Ziad A.
SITE TESTING IN SUMMER AT DOME C, ANTARCTICA Astron. Astroph., 444, 651
(2005)
Abstract :
We present summer
site testing results based on DIMM data obtained at Dome C,
Antarctica. These data have been collected on the bright star Canopus
during the 3-months summer campaings 2003-2004 and 2004-2005. We
performed continuous monitoring of the seeing and the isoplanatic
angle in the visible. We found a median seeing of 0.54 arcsec and a
median isoplanatic angle of 6.8 arcsec. The seeing appears to have a
deep minimum around 0.4 arcsec almost every day in late afternoon.
23. E. Aristidi, K. Agabi, M. Azouit, E. Fossat, J. Vernin, T.
Travouillon, J.S. Lawrence, C. Meyer, J.W.V. Storey, B. Halter, W.L.
Roth, and V. Walden
AN ANALYSIS
OF TEMPERATURES AND WIND SPEEDS ABOVE DOME C, ANTARCTICA Astron. Astroph., 430, 739
(2005)
Abstract :
A good astronomical
site must fulfill several criteria including low atmospheric
turbulence and low wind speeds. It is therefore important to have a
detailed knowledge of the temperature and wind conditions of a
location considered for future astronomical research. Antarctica has
unique atmospheric conditions that have already been exploited at the
South Pole station. Dome C, a site located on a local maximum of the
Antarctic plateau, is likely to have even better conditions. In this
paper we present the analysis of two decades of wind speed
measurements taken at Dome C by an automated weather station (AWS).
We also present temperature and wind speed profiles taken over four
Antarctic summers using balloon-borne weather sondes. We will show
that as well as having one of the lowest average wind speed ever
recorded at an existing or potential observatory, Dome C also has an
extremely stable upper atmosphere and a very low inversion layer.
Abstract :
We present relative
astrometric measurements of visual binaries made with the Pupil
Interferometry Speckle Camera and Coronograph (PISCO) at the 1-meter
Zeiss telescope of Brera Astronomical Observatory, in Merate. We
provide 135 new observations of 103 objects, with angular separations
in the range 0.1-4.0 arcsec and with an accuracy better than
0.01arcsec. Our sample is made of orbital couples as well as binaries
whose motion is still uncertain. Our purpose is to improve the
accuracy of the orbits and constrain the masses of the components.
This work already leads to the revision of the orbits of three
systems (ADS 5447, 8035 and 8739).
Abstract :
This paper
describes a method of beam-combination in the so-called
hypertelescope imaging technique recently introduced by Labeyrie in
optical interferometry. The method we propose is an alternative to
the Michelson pupil reconfiguration that suffers from the loss of the
classical object-image convolution relation. From elementary theory
of Fourier optics we demonstrate that this problem can be solved by
reconfiguring images instead of pupils. Imaging is performed in a
combined pupil-plane where the point-spread function (PSF) tends
towards a pseudo Airy disc for a sufficiently large number of
telescopes. Our method is applicable to snap-shot imaging of extended
sources with a field limited to the Airy pattern of single telescopes
operated in a co-phased multi-aperture interferometric array. It thus
allows to apply conveniently focal plane coronagraphy. Our technique
called Interferometric Remapped Array Nulling (IRAN) is particularly
suitable for high dynamic imaging of extra-solar planetary companions
or extra-galactic objects where long baseline interferometry would
closely probe the central regions of AGNs for instance. We also
discuss the application of IRAN to improve the performances of
imaging and/or nulling interferometers like the full-fledged VLTI
array or the DARWIN space-borne mission.
Abstract :
The first
astronomical seeing monitoring has been made with a DIMM instrument
at the Antarctic plateau site of Dome C in December 2002 on the
bright star Canopus (alpha Eri) during the daytime. In these far from
optimal conditions, a median seeing value of 1,20 arcsec has been
obtained, with extended periods better than 1 arcsec and 12 percent
of the time better than 0.75 arcsec.
19. J. L. Prieur, J. M. Carquillat, N. Ginestet, L. Koechlin, A.
Lannes, E. Anterrieu, S. Roques, E. Aristidi, and M. Scardia
SPECKLE
OBSERVATIONS OF COMPOSITE SPECTRUM STARS : II. Differential Photometry
of the Binary Components The Astroph. Journal Suppl. Series, 144, 263
(2003)
Abstract :
Multicolor
differential photometry measurements of the two components of 18
close binary stars, mostly composite spectrum stars, are presented.
They are based on observations made at Pic du Midi Observatory with
the speckle camera PISCO between 1993 and 1998. Optical bench
experiments were also performed to access the validity of the whole
process from the data acquisition with the ICCD detector to the final
photometry measurements. The results are discussed and compared with
(i) Hipparcos and speckle photometry, (ii) spectroscopic measurements
and (iii) composite spectra computed with a spectral library. Our
measurements are in good agreement with other observations. We also
determined the evolution stage of the individual components : the
absolute visual magnitudes of the cool giant stars that we found are
compatible withe calibrations made by other authors. This work shows
that PISCO is well adapted to efficiently perform relative photometry
of close binary stars.
18. Prieur J.L., Koechlin L., Ginestet N., Carquillat
J.-M., Aristidi E., Scardia M., Arnold L., Avila R., Festou M., Morel
S., Perez J.-Ph.
SPECKLE
OBSERVATIONS OF COMPOSITE SPECTRUM STARS WITH PISCO IN 1993-1998 The Astroph. Journal Suppl.
Series, 142, 95 (2002)
Abstract :
We present speckle
observations of a list of 47 composite spectrum stars made at Pic du
Midi Observatory between 1993 and 1998. This represents wore than 150
independent 10 mn sequences of observations with a companion
detection rate of 76%. The angular separations range from 1"2 to
~0"05. Three high sensitivity detectors were used : the CAR, the
ICCD and the PAPA. We also give a series of 23 measurements of an
additionnal list of 9 close binaries and confirm the duplicity of HD
156729 (HR 6436) discovered by Hipparcos, with a large difference of
magnitudes (delta m =4.2).
17. Prieur J.L., Aristidi E., Lopez B., Scardia M., Mignard F.,
Carbillet M.
HIGH
ANGULAR RESOLUTION OBSERVATION OF LATE-TYPE STARS The Astroph. J. Suppl. 139, 249-258 (2002)
Abstract :
This paper presents
speckle observations of Mira (o Ceti) and late type stars with the
PISCO speckle camera of Pic du Midi in the period 1995-1998. A survey
for binarity among a sample of late type stars was performed
,which led to 7 positive detections out of 36 objects.
Photomertric and color variations of the companion of Mira were
search for, but no significant brightness variation could be found
over time scale of ~ 5-10 mn. The position and photometry
measurements, the restored image with high angular resolution of the
binary system Mira A-B (ADS 1778) are in full agreement with HST data
obtained at the same epoch. A new orbit has been derived for
Mira A-B.
16. Scardia M., Prieur J.L., Koechlin L., Aristidi E.
ORBITAL
ELEMENTS OF SIX VISUAL BINARY STARS Astron. Nachr.322, 161-169(2001)
Abstract :
Revised orbital
elements of the visual binary stars STT 515, BU 4 AB, STF 183 AB,
A 207, STT 43 and A 2413 are given. Dynamical parallaxes and total
masses of the systems have been calculated.
AMBER : THE
NEAR INFRARED FOCAL INSTRUMENT FOR THE VERY LARGE TELESCOPE
INTERFEROMETER C.R. Acad. Sci., Paris, T.2, série IV,
67--77 (2001)
Abstract :
AMBER is the
General User near-infrared focal instrument of the Very Large
Telescope interferometer. Its specifications are based on three key
programs on Young Stellar Objects, Active Galactic Nuclei central
regions, masses and spectra of hot Extra Solar Planets. It has an
imaging capacity because it combines up to three beams and very high
accuracy measurements are expected from the spatial filtering of
beams by single mode fibers and the comparicon of measurements made
simultaneously in different spectral channels.
14. Prieur J.L., Oblak E., Lampens P., Kurpinska-Winiarska M.,
Aristidi E., Koechlin L., Ruymaekers G.
SPECKLE
OBSERVATIONS OF BINARY SYSTEMS MEASURED BY HIPPARCOS Astron. Astroph 367,
865-875 (2001)
Abstract :
From speckle
observations made with the PISCO speckle camera at the Pic du Midi
observatory, we present high angular resolution astrometric data for
43 binary stars already observed by the Hipparcos satellite. This
sample consists of mainly new Hipparcos eclipsing binaries with a
visual companion closer than one arcsecond, choosen with the aim to
study the dynamical implications of a third component on the
observationnal parameters of the eclipsing systems. In addition, we
also included a sample of close visual binaries with few speckle data
in order to analyse systematic departures between the speckle and
non-speckle orbits. The reduction method and the results are
presented in detail. For the close visual binaries we confront our
observations with the epemerides based on the best known orbits. For
the wide visual binaries the confrontation is made directly with the
Hipparcos data. Our observations are consistent both with the
previous speckle data and with most of the Hipparcos measurements.
13. Scardia M., Prieur J.L., Aristidi E., Koechlin L.
ORBITAL
ELEMENTS OF FIVE CLOSE VISUAL BINARY STARS Astron. Nachr.321, 255--262 (2000)
Abstract :
Revised orbital
elements of the visual binary stars STT 2, STT 4, BU 1015, STT 6 and
BU 395 are given. Dynamical parallaxes and total masses of the
systems have been calculated.
12. Scardia M., Prieur J.L., Aristidi E., Koechlin L.
SPECKLE
OBSERVATIONS OF DOUBLE STARS WITH PISCO AT PIC DU MIDI : MEASUREMENTS
IN 1998 The Astrophys. Journal Suppl. 131, 561--569 (2000)
Abstract :
We
present astrometric measurements of binary stars based on speckle
observations of 164 independent sequences of observations (~10000
frames each) made with the PISCO speckle camera at Pic du Midi. The
measurements concern 147 objects, of which 134 were found to be
double with a separation in the range 0"1-1"0. These
objects were mainly selected amond grade 3 orbits to improve the
accuracy of their orbits and to constrain their masses. We discovered
the binarity of 59 Aql with an angular separation of 0"09 +/-
0"01.
11. Aristidi E., Prieur J.L., Scardia M., Avila R., Carbillet M.,
Lopez B., Rabbia Y., Koechlin L., Nisenson P., Ghezari D.
SPECKLE
OBSERVATIONS OF DOUBLE AND MULTIPLE STARS AT PIC DU MIDI :
MEASUREMENTS DURING 1995 AND 1997 AND NEW ORBITS Astron. Astrophys. Suppl. Series134, 545--552 (1999)
Abstract :
We present speckle
observations of 48 double and multiple stars observed with the
2-meter ``Télescope Bernard Lyot'' (TBL) in December 1995, January
1997 and June 1997. Angular separations, absolute position angles and
relative photometry result from these observations. New orbital
elements have been recalculated for 8 double stars.
Abstract :
We present speckle
observations of nineteen double stars and the triple star 2 Cam.
Angular separations, absolute position angles and relative photometry
result from these observations. The angular separation is derived
from the power spectrum. The position angle and the relative
photometry are determined by two recent techniques: the
cross-correlation between the speckle images and their square, and
the ratios of twofold probability density functions of the images.
Abstract :
We present in this
paper a technique for imaging binary stars from speckle data. This
technique is based upon the computation of the cross-correlation
between the speckle frames and their square. This may be considered
as a simple, easy to implement, complementary computation to the
autocorrelation function of Labeyrie's technique for a rapid
determination of the position angle of binary systems. Angular
separation, absolute position angle and relative photometry of binary
stars can be derived from this technique. We show an application to
the bright double star zeta Sge observed at the 2 m Bernard Lyot
telescope.
Abstract :
The
probability imaging technique applied to double stars speckle data is
presented within the framework of a new approach, giving more
directly the intensity ratio and relative position of the components.
The twofold probability density function is used for this purpose. A
theoretical model is developed, pointing out a relevant quantity
deduced from the twofold probability density functions of the binary
system and a nearby reference star. A method using this quantity is
proposed to reconstruct the binary system, together with a
reference-less version of it. The practical implementation of the
method is tested for limiting cases and is improved by numerical
simulations. Making use of the resulting procedure, intensity ratios
and relative positions of the components are obtained for three close
binary stars: beta Del, Moai 1 and gamma Per.
Abstract :
The effect of
atmospheric turbulence on the imaging of scenes, for an horizontal
propagation of the light over a distance of 20km, 15 meters above the
sea surface, was analyzed at visible wavelength using a 20cm
telescope. Point-sources images were recorded during the night, and
the Fried parameter r0 was derived using several methods, leading to
r0 values ranging from 2 to 4cm depending on observing conditions. A
very high level of scintillation was observed. Studies of
correlations between close-by sources lead to a very small domain of
isoplanatism. Daytime observations of an extended source are also
performed; an image motion of small spatial coherent length seems to
be drawn by an horizontal
wind producing wave-like distortion of
horizontal lines and boiling-like of vertical ones.
Abstract :
We report in this
letter the discovery of a close double star. The binarity of the
bright star SAO 12917 is determined from visible speckle
interferometry with the Bernard Lyot telescope. The sepa ration and
the position angle of the binary system are measured together with a
relative photometry in the three visible spectral bands B, V and R.
The data reduction is performed making use of a cross-correlation
technique, derived from the speckle masking technique. We discuss the
nature of the components and roughly estimate that the period of this
double star system is about 13 years.
Abstract :
This paper present
numerical illustrations of the effects of clipping of photoevents in
speckle interferometry and speckle masking. The clipping is due to a
saturation of the photon-counting detectors that cannot count more
than one photon per pixel, causing the image to be composed of ``0"
and ``1". The theoretical basis for this study has been
published by Aime and Aristidi (1992). Clipping effects are
investigated numerically on real star data. As predicted by theory,
the clipping introduces several effects on auto and triple
correlation functions, such as a linear global loss of energy, and
non linear terms which affects mainly the high frequencies. Attention
is focused on the way the astronomical information is affected by
this kind of detection, especially for the case of the double stars.
Abstract :
We
use the Richardson-Lucy algorithm to deconvolve a set of images which
are gray-levels representations of twofold probability density
functions (PDF). The PDF of the true signal is blurred by the PDF of
the noise. The deconvolution is first performed on simulated data,
for two levels of additive noise, i.e. for two different widths of
the blurring function. These images are linked to one another,
and we check the goodness of the deconvolution procedure by verifying
that the properties of the image power spectrum (a quantity that is
derived from the whole set of PDFs) are well conserved during the
deconvolution. We discuss thequality of the result, which depends of
the number of iterations, and analyze the problems produced by an a
priori "support constraint" (i.e. a limited domain of
values) on the images. An application is made to real physical data.
3. Aime C., Aristidi E., Lantéri H., Ricort G.
USE OF A
REFERENCE SOURCE IN PROBABILITY IMAGING Applied Optics, 32, 2747-2757 (1993)
Abstract :
We describe the
relations between the statistics of the speckled image I(x) that is
produced by an astronomical object at the focus of a telescope and
the statistics of the point-source speckle pattern S(x) that is
obtained under comparable conditions of turbulence. We show that the
characteristic function (CF) of I(x) can be written as a central
slice of a higher order CF of S(x); as a consequence, probability
density functions of I(x) and S(x) are related to one another by
means of projections. An illustration, consisting of one-dimensional
scans obtained with the European Southern Observatory's slit-scanning
infrared specklograph, is made or real data. It is shown how the
onefold and the twofold PDF's of a double star can be synthesized
from the twofold ans the threefold PDF's of the reference source.
2. Aime C., Aristidi E.
STATISTICAL
APPROACH TO BIAS EFFECTS IN THE TECHNIQUES OF SPECKLE INTERFEROMETRY
AND SPECKLE MASKING J. Opt.Soc. Am. A, 9, 1812-1821 (1992)
Abstract :
We present an
approach to the speckle interferometry techniques of Labeyrie and
Weigelt that is based on the use of the moment generating function
(MGF). The remarkable properties of the MGF 's of photodetected
images make it possible to obtain the expression for the photon-bias
terms by a method completely different from the usual Goodman-Belsher
approach [J.W. Goodman, Statistical optics, (Wiley, New York, 1985)].
It gives us the mathematical relations to predict the effects of a
clipped photodetection of the image on the autocorrelation and triple
correlation functions. As a result, clipping ruins the linear
relationship between object and reference source for these functions.
The effect of photon recentering is also investigated and directly
related to a single-photon clipping effect. Analytical expressions
for a normal speckle pattern are
given.
1. Aime C., Aristidi E.
PROBABILITY
IMAGING : THE STATISTICS OF SPECKLE PATTERNS OF EXTENDED ASTRONOMICAL
SOURCES AT HIGH LIGHT LEVEL J. Opt.Soc. Am. A , 8, 1434-1441 (1991)
Abstract :
Assuming that the
complex amplitude of the wave at the focus of a large telescope is
Gaussian and making use of a technique of orthonormal expansion, we
give a mathematical expression for the characteristic function of any
order of the speckle pattern of an extended astronomical object as
the inverse of the determinant of a matrix whose elements are defined
by the spatial correlation function of the amplitude of the
point-source speckle pattern and a diagonal matrix representing the
astronomical object. This mathematical model is intended to be used
in an inverse procedure to find the object most compatible with the
observed spatial statistical properties. An exemple of application is
given for a double star.
Communications
104. Phung D.A., Samain E., Chabé J., Courde C., Ziad A., Giordano C., Ziad A., Aristidi E. et al.,
Optical bench development for laser communication OSIRIS mission at Grasse (France) station
International Conference on Space Optics 2020, virtual conf., 30 March - 2 April 2021
Abstract :
The Grasse Satellite Laser Ranging (SLR) station (ID7845), part of the International Laser Ranging Service (ILRS) network, participates to various laser applications including SLR, Lunar Laser Ranging (LLR), Time Transfer by Laser Link (T2L2), high-resolution imagery, and debris detection. Since 2014, in collaboration with the France Space Agency (CNES), the Grasse station has been upgrading in order to be able to take part in laser communication (lasercom) experiments. The main challenges of these experiments are the implementation of a complete laser communication chain from space to ground and the characterization of the turbulent atmosphere during the optical data transfer. Several campaigns have been successfully performed and planned since 2015 between Grasse station and LaserComm terminal at low Earth orbit, SOTA onboard SOCRATES [NICT ref], OPALS integrated on ISS [NASA ref], and recently DLR’s OSIRIS mission. To prepare for possible higher data-rate LaserComm campaigns in the near future (OSIRISv1 at 40 Mbps, OSIRISv2 & Optelµ at 1 Gbps, OSIRISv3 at 10 Gbps) Grasse SLR station is upgrading on LaserComm optical bench, with a fine auto-tracking system and a high sensitivity telecom detector. In the proceeding, we will describe the architecture of our optical bench for high data-rate lasercom link and some primary results of the lasercom link between OSIRISv1 (onboard FlyingLaptop satellite) and the station.
103. Rafalimanana A., Giordano C., Ziad A., Aristidi E.,
Towards an optimal prediction of atmospheric turbulence by means of WRF model
International Conference on Space Optics 2020, virtual conf., 30 March - 2 April 2021
Abstract :
The performance of ground-based astronomical observations suffers from atmospheric turbulence and meteorological conditions. The a priori knowledge of atmospheric turbulence conditions several hours before observations allows to optimize the programmation of astronomical observations (flexible scheduling). In this communication we present a prediction study based on the Weather Research and Forecast (WRF) model. It allows to predict and characterize the useful set of meteorological parameters relevant to atmospheric physics (e.g. pressure, temperature, relative humidity, wind speed and wind directon). Predicted parameters are
then injected into a turbulence model to compute the refractive index structure parameter Cn2 and infer optical turbulence integrated parameters such as the seeing, isoplanatic angle, Fried parameter and the coherence time. We perform sets of simulations for Cerro Pachon Observatory using the data from the National Centers for Environmental Prediction (NCEP)
Climate Forecast System Reanalysis (CFSR). An important question is how accurately numerical weather prediction models can reproduce conditions over the complex terrain of Cerro Pachon area. In order to produce a reliable forecast, meteorological prognostic skills need accurate representations of the physical parameterization options including Planetary Boundary Layer (PBL) schemes, Microphysics, Cumulus, Land-surface models, Radiation schemes. Three widely used PBL schemes (Yonsei University (YSU), Asymmetrical Convective Model version 2 (ACM2), and Mellor-Yamada-Janjic (MYJ)) and two Land Surface Model (LSM) (Rapid Update Cycle (RUC) and Noah) were tested, analysed and compared in order to find the optimal WRF configuration. Predictions are compared to real data coming from ground-based meteorological observations and balloon-borne radiosoundings. It is determined that
WRF, coupled with the YSU planetary boundary layer scheme and RUC land surface model give the most reliable solutions in the Cerro Pachon Obervatory area. Seasonal statistics are also presented for different weather and turbulence parameters.
102. Giordano C., Ziad A., Aristidi E., Chabé J, Fantei-Caujolle Y., Renaud C., Rafalimanana A.,
CATS: continuous turbulence characterization for both optical link and astronomical support
International Conference on Space Optics 2020, virtual conf., 30 March - 2 April 2021
Abstract :
The optical turbulence measurement and characterization has become an essential information for optical link (telecommunication, telemetry, time transfert, ...) and for high-angular resolution imaging in astronomy. For example, it has an impact on the quality and on the bit error rate of optical communication signals and it decrease the resolution of astronomical images. The J.L. Lagrange Laboratory of the Observatoire de la Cote d'Azur has a long and recognized expertise in atmospheric optics and turbulence for astronomical purposes. We have developed recently a new generation of autonomous instruments for daytime and nighttime
atmospheric optical turbulence measurement. In 2015, a complete instrumental platform, the Calern Atmospheric Turbulence Station (CATS) has been installed at the Calern observatory. CATS is an automatic station equipped with a set of complementary instruments using original techniques for monitoring optical turbulence from the first meters above the ground up to the top of the atmosphere including the dome seeing. The station is based on 4 instruments. PML measures continuously the vertical profiles of the refractive index structure constant Cn2 with a high vertical resolution (100m at ground level). GDIMM monitors the wavefront coherence parameters (seeing, isoplanatic angle, coherence time, scintillation, outer scale). A weather station provides the ground meteorological conditions (pressure, temperature, relative humidity, wind speed and direction). And the nighttime cloud fraction is given by an all-sky camera. Another instrument called INTENSE (INdoor TurbulENce Sensor) is occasionally associated with CATS station to measure the seeing inside the dome of the 1.5m MeO telescope to evaluate its contribution to the whole turbulence. The last tool integrated to the CATS station is a forecasting model using the Weather Research and Forecasting (WRF) system coupled to a turbulence model to predict daytime and nighttime meteorological and optical turbulence conditions for the next 48h.
Monitoring the atmospheric turbulence profile with high vertical resolution with the PML instrument
SPIE Astronomical Telescopes + Instrumentation, 2020, 14-18 Dec 2020
Abstract :
Wide-Field Adaptive Optics systems will be a key component of the future generation of Extremely Large Telescopes.
All the components of such Adaptive Optics systems have to be precisely specified using the atmospheric
turbulence parameters of the site, particularly the profile of the refractive index structure constant C2n(h). The
monitor PML (Profiler of Moon Limb), for the extraction of the C2n(h) profile with high vertical resolution for
nighttime and daytime conditions, has been developed and is now routinely exploited at the Calern Observatory
(French Riviera). The PML instrument uses a differential method with two small subapertures mask through
which the Moon limb or Sun edge are observed leading to a continuum of double stars allowing a scan of the
whole atmosphere with high resolution in altitude. In addition, PML provides, in real time, a complete characterization
of the atmospheric turbulence since it is able to measure the other turbulence parameters like the
total seeing and the isoplanatic angle.
100. Giordano C., Rafalimanana A., Ziad A., Aristidi E., Chabé J, Fantei-Caujolle Y., Renaud C.,
Statistical Learning as a new approach for optical turbulence forecasting
SPIE Astronomical Telescopes + Instrumentation, 2020, 14-18 Dec 2020
Abstract :
For the new generation of Extremely Large Telescopes the knowledge of atmospheric turbulence conditions is
become an information of primary importance to design and optimize all focal instrumentation. In the same way,
the forecast of these atmospheric conditions is also of interest to allow both flexible scheduling and long term
site testing. Until now we have used weather forecast tools coupled with turbulence models to predict turbulence
conditions. In addition, we are developing a predictive statistical learning tool, using a large atmospheric
database. Since 2015, the Calern Observatory hosts the Calern Atmospheric Turbulence Station (CATS) which
measures during daytime and nighttime, ground meteorological conditions, vertical profiles of the C2n
and all
relevant integrated parameters characterizing the optical turbulence. This large CATS database is used as input
for our predictive statistical learning tool. This latter should take into account more closely the local specificities,
seasonal variations and day/night transitions. A comparison between turbulence predictive models and statistical
learning tools is presented and discussed.
99. Ziad A., Aristidi E., Chabé J, Fantei-Caujolle Y., Renaud C., Giordano C.
Which isoplanatic patch size for High Angular Resolution Techniques ?
SPIE Astronomical Telescopes + Instrumentation, 2020, 14-18 Dec 2020
Abstract :
The isoplanatic patch size is of interest to reach a high performance with an Adaptive Optics system, since the reference star for its calibration should be located in the same isoplanatic domain than the science source. Different techniques and methods have been developed leading to estimations of the isoplanatic patch but all are model-dependent. We first present a review of these techniques and methods of isoplanatic patch size measurement. We developed a new technique for the estimation of the isoplanatic angle based on an extended object. This technique is now part of our new turbulence profile monitor PML based on the observation of the
Moon limb or Sun edge. The first statistics of the isoplanatic angle with this new technique are presented and compared to the exiting techniques based on scintillation measurements or other turbulence parameters such as Fried parameter and/or C2n profile.
98. Rafalimanana A, Giordano C., Ziad A., Aristidi E.
Towards an optimal prediction of atmospheric turbulence by means of WRF model
SPIE Astronomical Telescopes + Instrumentation, 2020, 14-18 Dec 2020
Abstract :
Forecasts of meteorological and atmospheric turbulence conditions are important for optical link optimization in laser
telemetry, for free space telecommunications reliability and optical imaging systems. It has become a necessary information for an optimal programming of the ground-based astronomical observations, called "flexible scheduling". In this study, we present the ability of the Weather Research and Forecasting (WRF) model to predict the meteorological parameters (temperature, relative humidity, wind speed and wind direction) as well as the optical turbulence conditions (profile of the refractive index structure parameter Cn2, seeing, Fried parameter, isoplanatic angle and coherence time) above Cerro Pachon Observatory in Chile. Radiosounding balloons and mast based observations have been used to evaluate the model performance. We will show that WRF model can reach a good agreement with the radiosoundings measurements.
97. Cottalorda E, Aristidi E., Carbillet M, Guinard, M., Vour’ch S.
Post-AO image reconstruction with the PSE algotithm
SPIE Astronomical Telescopes + Instrumentation, 2020, 14-18 Dec 2020
Abstract :
We propose, in the framework of short-exposure high angular resolution imaging, a new technique denoted as Power Spectrum Extended (PSE). This method allows to perform direct imaging of extended objects from a series of short-exposure frames, and is well adapted to post-adaptive optics images and/or small diameter telescopes. The algorithm works in the Fourier domain. It combines information from the average power spectrum of images with phase information estimated from an ad hoc shift-and-add process. It can be used together with a Lucky Imaging selection algorithm. It gives very encouraging results, especially on very extended objects (greater than the isoplanatic angle) and at low light level (photon counting). In this communication, we present results obtained on astronomical objects as well as artificial satellites. We also show a comparison of performance compared to other speckle and Lucky Imaging techniques.
96. Aristidi E., Fantei-Caujolle Y., Ziad A., Chabé J, Giordano C., Renaud C., Rafalimanana A.,
Turbulence monitoring at Calern observatory with the Generalised Differential Image Motion Monitor
SPIE Astronomical Telescopes + Instrumentation, 2020, 14-18 Dec 2020
Abstract :
The Generalised Differential Image Motion Monitor (GDIMM) was proposed a few years ago as a new generation instrument for turbulence monitoring. It measures integrated parameters of the optical turbulence, i.e the seeing, isoplanatic angle, scintillation index, coherence time and wavefront coherence outer scale. GDIMM is based on a fully automatic small telescope (28cm diameter), equipped with a 3-holes mask at its entrance pupil. The instrument is installed at the Calern observatory (France) and performs continuous night-time monitoring of turbulence parameters. In this communication we present long-term and seasonnal statistics obtained at Calern, and combine GDIMM data to provide quantities such as the equivalent turbulence altitude and the effective wind speed.
95. Aristidi E., Cottalorda E., Carbillet M., Abe L., Makki K., Rivet J.P., Vernet D., Bendjoya P.,
The power spectrum extended technique applied to images of binary stars in the infrared
SPIE Astronomical Telescopes + Instrumentation, 2020, 14-18 Dec 2020
Abstract :
We recently proposed a new lucky imaging technique, the Power Spectrum Extended (PSE), adapted for image reconstruction of short-exposure astronomical images in case of weak turbulence or partial adaptive optics correction. In this communication we show applications of this technique to observations of about 30 binary stars in H band with the 1m telescope of the Calern C2PU observatory. We show some images reconstructed at the diffraction limit of the telescope and provide measurements of relative astrometry and photometry of observed couples.
94. Cottalorda E., Aristidi E., Carbillet M., Guinard M., Vourc'h S
Power spectrum extended, a new reconstruction method for post-adaptive optics short exposure imaging
Workshop on wavefront sensing in the VLT/ELT era V, virtual workshop, 13-15 Oct 2020
Abstract :
We propose, in the framework of short-exposure and post-adaptive optics (AO) imaging, a new technique denoted as Power Spectrum Extended (PSE). This method allows to perform direct high-angular resolution imaging from a series of short-exposure frames. It is well adapted to post-AO data. The algorithm works in the Fourier domain. It combines information from the average power spectrum of images with phase information estimated from an ad hoc shift-and-add process. It can be used together with a Lucky Imaging selection algorithm. In this poster, we present our PSE technique together with results on simulated post-AO images.
93. Cottalorda E., Aristidi E., Carbillet M., Guinard M., Vourc'h S
Power Spectrum Extended: Preliminary results
SF2A-2019, Nice (France), 14-17 May 2019
Abstract :
We propose, in the framework of short-exposure high-angular-resolution imaging (Lucky Imaging, speckle techniques), a simple improvement of the original Labeyrie's speckle interferometry technique. This new method, denoted as Power Spectrum Extended, allows to perform direct imaging of extended objects in the case of post-adaptive optics images and/or small diameter telescopes. The algorithm works in the Fourier domain. It combines informations from the average power spectrum of an ensemble of images with phase information estimated from an ad hoc shift-and-add process. It can be used together with a Lucky Imaging selection process. Preliminary results are presented, with application to images of both an astronomical object and an artificial satellite.
Abstract :
The optical turbulence forecasting has become a necessary information for an optimal programmation of the astronomical observations, called "flexible scheduling". We propose the prediction of the optical turbulence by means of the Weather Research and Forecasting (WRF) model combined with an optical turbulence model. We performed a set of simulations to obtain a 24-hours period forecast for optical turbulence parameters above the Calern observatory. We present the results of our forecasting and comparisons with the CATS (Calern Atmospheric Turbulence Station) measurements.
Abstract :
The Profiler of Moon Limb (PML) is a recent instrument dedicated to the monitoring of optical turbulence profile of the atmosphere. Fluctuations of the Moon or the Sun limb allow to evaluate the index refraction structure constant Cn2(h) and the wavefront coherence outer scale L0(h) as a function of the altitude h. The atmosphere is split into 33 layers with an altitude resolution varying from 100m (at the ground) to 2km (in the upper atmosphere). Profiles are obtained every 3mn during daytime and nighttime. We report last advances on the instrument and present some results obtained at the Plateau de Calern (France).
90. Giordano C., Rafalimanana A., Ziad A., Aristidi E., Chabé J., Fantei-Caujolle Y., Renaud C.,
Optical turbulence forecasting and comparisons with daytime and nighttime measurements
AO4ELT6, Québec (Canada), 9-14 June 2019
Abstract :
Forecasting the optical turbulence has become a necessary information to plan astronomical observations in the best
possible way and to avoid scientific and pecuniary losses. This planification, called the "flexible scheduling", has been studied from
different viewpoints in the past. Our choice is to use the Weather Research and Forecasting model coupled with different turbulence
models to compare and analyse a set of possible options. At this point, the model mainly used in our group has been developed
empirically from a large amount of balloons sounding. We present, in this paper, a study of a forecasting above the Calern observatory
and comparisons with daytime and nighttime optical measurements obtained by the Calern Atmospheric Turbulence Station (CATS).
We will show that we can reach a good precision above the Calern site, mainly above an altitude of a few hundreds meter, by binding
the model with measurements. We will also present a user-friendly tool in development which will allow users to run predictions above
different regions every where in the world using different sets of parametrization.
89. Ziad A., Chabé J., Fantei-Caujolle Y., Aristidi E., Renaud C., Giordano C.
CATS: a new autonomous station for atmospheric turbulence characterization
AO4ELT6, Québec (Canada), 9-14 June 2019
Abstract :
The Observatoire de la Côte d'Azur and the J.L. Lagrange Laboratory have a long
recognized expertise in Atmospheric Optics. The Calern Observatory took benefits from this experience and has
been equipped with a station of atmospheric turbulence measurement (CATS: Calern Atmospheric Turbulence
Station). The CATS station is equipped with a set of complementary instruments for monitoring atmospheric
turbulence parameters. These new-generation instruments are autonomous for a fully monitoring of the turbulence
within original techniques for measuring optical turbulence since the first meters above the ground to the borders of
the atmosphere. The CATS station provides a real-time turbulence conditions over the Calern Observatory. The
CATS station is a support involved in many scientific and educational projects at the Calern observatory such as an
ongoing study of turbulence impact on the laser links of the MeO Laser Ranging Station, development of Adaptive
Optics projects and on site training for students of the international master in Astrophysics (MAUCA) and OPTICS
through the organization of on-sky practical works.
88. Aristidi E., Fantei-Caujolle Y., Chabé J., Renaud C., Ziad A., Ben Rahhal M.
Turbulence monitoring at the plateau de Calern with the GDIMM instrument
SPIE conf on Astronomical Telescopes + Instrumentation, Austin (Texas), 10-15 June 2018
Abstract :
We present some statistics of turbulence monitoring at the Plateau de Calern (France), with the Generalised Differential Image Motion Monitor (GDIMM). This instrument allows to measure integrated parameters of the atmospheric turbulence, i.e. seeing, isoplanatic angle, coherence time and outer scale, with 2 minutes time resolution. It is running routinely since November 2015 and is now fully automatic. A large dataset has been collected, leading to the first statistics of turbulence above the Plateau de Calern.
87. Ziad A., Chabé J., Fantei-Caujolle Y., Aristidi E., Renaud C., Ben Rahhal M.
CATS: an autonomous station for atmospheric turbulence characterization
SPIE conf on Astronomical Telescopes + Instrumentation, Austin (Texas), 10-15 June 2018
Abstract :
From its long expertise in Atmospheric Optics, the J.L. Lagrange Laboratory of the Observatoire de la Côte d'Azur has developed a new generation of autonomous stations of atmospheric turbulence measurement. Since two years, the Calern Observatory is equipped with this kind of stations called CATS for Calern Atmospheric Turbulence Station. CATS is an autonomous station consisting of a set of complementary instruments within original techniques for measuring optical turbulence since the first meters above the ground to the borders of the atmosphere including the dome seeing. Indeed, one of the CATS instruments is the PML (Profiler of Moon Limb) measuring the vertical distribution of turbulence using lunar and solar limbs with a resolution reaching 100m in the ground layer. The second instrument is a Generalized DIMM dedicated to provide wavefront parameters at ground level (seeing, outer scale, coherence time and isoplanatic angle). A third instrument called INTENSE (INdoor TurbulENce Sensor) is occasionally associated with CATS station to measure the turbulence inside the dome of the 1.5m MeO telescope to evaluate its contribution to the whole turbulence. The CATS station is also a support for our educative activities as part of our Masters in Astronomy and Optics, through the organization of on-sky training works.
86. Chabé J., Giauffret T., Phung D, Ziad A., Aristidi E., Ben Rahhal M., Samain E., Fantei-Caujolle Y.
Study of the local optical turbulence in a 1.5m telescope dome with the INTENSE instrument
SPIE conf on Astronomical Telescopes + Instrumentation, Austin (Texas), 10-15 June 2018
Abstract :
Optical systems performances can be affected by local optical turbulence created by its surrounding environment (telescope dome, clean room, atmospheric surface layer). We present recent measurements of the local turbulence inside the 1.5m ?eO telescope dome at Calern observatory (France) with the INTENSE (INdoor TurbulENce SEnsor) instrument. Relationships between the dome turbulence and the local meteorological measurements (temperature, pressure, wind speed and direction) are investigated. The impact of the local dome turbulence on the seeing at the focal plane of the 1.5 m telescope is highlighted.
85. Crouzet N., Mékarnia D., Bayliss D.D.R., D., Guillot T., Abe L., Agabi A., Fantéi-Caujolle Y., Gillon M., Zhou G., Rivet JP., Chapellier E., Schmider F.X., Gonçalves I., Daban J.B., Gouvret C., Aristidi E., Fruth T., Erikson A., Rauer H., Bondoux E., Challita Z., Pouzenc C., Jehin E., Fressin F., Valbousquet F., Blazit A., Bonhomme S., Bouchy F., Gerakis J., Bouchez G.
A 76 day period G-M eclipsing binary discovered from Dome C, Antarctica
SCAR/IASC Open Science Conference, Davos, Switzerland, 15-26 June 2018
Abstract :
M-dwarfs account for 75% of stars in the Milky Way. However, their properties are not well understood and significant discrepancies exist between model predictions and observations. Low mass stars in detached eclipsing binaries are the most valuable objects to study because their radius, mass, and temperature can be measured. The vast majority of systems that have been characterized to date have short orbital periods (less than 10 days), yielding a strong coupling between both stars. Sampling a larger parameter space is mandatory to explore the observed discrepancies. The four month continuous night during the Antarctic winter combined with excellent weather conditions is favorable to the detection of variable objects including with long periods. We observed a field centered on the celestial South pole during four winters with the ASTEP South instrument, a 10 cm refractor in a thermalized box installed at Dome C, Antarctica, and detected a 76 day period G-M eclipsing binary. In this talk, we present this discovery, the follow-up observations of this object, and investigate the properties of the M dwarf. At such a long orbital period, both stars are largely decoupled making this system a unique benchmark for the study of low mass stars. We also present some results about the characterization of Dome C for photometry in the visible.
84. N. Crouzet, E. Chapellier, D. Mékarnia, T. Guillot, L. Abe, A. Agabi, Y. Fantéi-Caujolle, D.D.R. Bayliss, G. Zhou, J.-P. Rivet, F.-X. Schmider, I. Gonçalves, J.-B. Daban, C. Gouvret, E. Aristidi, T. Fruth, J. Szulagyi, A. Erikson, H. Rauer, E. Bondoux, Z. Challita, C. Pouzenc, F. Fressin, F. Valbousquet, A. Blazit, S. Bonhomme, F. Bouchy, J. Gerakis, and G. Bouchez
Detection of transiting planet candidates and variable stars with ASTEP at Dome C
4th SCAR AAA 2017 Workshop, Chiang Mai, Thailand, 31 July – 4 August, 2017
Abstract :
Between 2008 and 2013, the ASTEP project aimed at discovering and characterizing extrasolar planets and variable stars from Dome C in Antarctica and at determining the quality of this site for photometry in the visible. Two instruments were deployed: a 40 cm Newton telescope designed to perform high precision photometry under the extreme conditions of the Antarctic winter, and a 10 cm refractor installed in a thermalized box pointing towards the celestial South pole. These instruments observed almost continuously during four winters and we extracted lightcurves for thousands of stars. In this talk, I will focus on the performances of the instruments and on our search for transiting planet candidates and variable stars in the lightcurves. The exceptional phase coverage allows us to detect variable objects with long periods as well as period and amplitude variations over the years. I will present new objects that we identified with ASTEP and I will show a detailed analysis of some of the most interesting ones.
83. Ziad A., Chabé J., Fantéi-Caujolle Y. Aristidi E., Renaud C.
CATS: a new station for a complete characterization of atmospheric turbulence
AO4ELT 5, Tenerife, Canary Islands, June 25-30, 2017
Abstract :
Since autumn 2015, the Observatoire de la Côte d'Azur and the J.L. Lagrange Laboratory have equipped the Calern Observatory with a new generation station of atmospheric turbulence measurement (CATS: Calern Atmospheric Turbulence Station). The CATS station is equipped with a set of complementary instruments for monitoring atmospheric turbulence parameters. These new-generation instruments are autonomous for a fully monitoring of the turbulence within original techniques since the first meters above the ground to the borders of the atmosphere. The CATS station provides a real-time turbulence conditions over the Calern Observatory. The CATS station is a support involved in many scientific and educational projects at the Calern observatory such as an ongoing study of turbulence impact on the laser links of the MeO Laser Ranging Station, development of Adaptive Optics projects and on site training for students of the international master in Astrophysics (MAUCA) and Optics through the organization of on-sky practical works.
Representation of Signals as Series of Orthogonal Functions
EAS Publications Series, Volume 78-79, p.99 (2016)
Abstract :
This paper gives an introduction to the theory of orthogonal projection of functions or signals. Several kinds of decomposition are explored: Fourier, Fourier-Legendre, Fourier-Bessel series for 1D signals, and Spherical Harmonic series for 2D signals. We show how physical conditions and/or geometry can guide the choice of the base of functions for the decomposition. The paper is illustrated with several numerical examples.
81. Crouzet N., Mékarnia D., Guillot T., Abe L., Agabi A., Fantéi-Caujolle Y., Bayliss G., Zhou G., Rivet JP., Schmider F.X., Gonçalves I., Daban J.B., Gouvret C., Aristidi E., Fruth T., Szulagyi J., Erikson A., Rauer H., Bondoux E., Challita Z., Pouzenc C., Fressin F., Valbousquet F., Blazit A., Bonhomme S., Bouchy F., Gerakis J., Bouchez G.
Analysis of four-winter photometric lightcurves obtained by ASTEP South at Dome C
SCAR 2016, conf. on Astronomy and Astrophysics from Antarctica, Kuala Lumpur, August 2016
Abstract :
ASTEP South is part of the ASTEP project that aims to determine the quality of Dome C for photometry in the visible and to discover and characterize extrasolar planets. ASTEP South consists of a front-illuminated 4k x 4k CCD camera, a 10 cm refractor, and a simple mount in a thermalized enclosure observing a 4x4 square degree field of view centered on the celestial South pole. ASTEP South has been observing nearly continuously for 4 winters, collecting about 30 TB of science data. We present the full analysis of these data. The observing mode of ASTEP South, with stars moving around the CCD with a 1-sidereal day period, make the data reduction particularly challenging. We describe the procedures that we specifically developed for these data as well as the corrections of various effects that affect the photometry. We extract the lightcurves for 6000 stars over 4 winters. Using this unique data base, we infer the quality of Dome C for photometry from the lightcurves themselves, and we search for periodic signals. Comparisons with similar instruments located at temperate sites show the advantage of the continuous phase coverage that can be achieved from Dome C. In particular, we detect long period transit signals that could hardly be detected from temperate sites. As an example, we present the detection of a long-period eclipsing binary system and the follow-up observations of this object, which will allow us to constrain the evolution models of low-mass stars. These results are very encouraging for time-series photometry from Dome C.
80. Chabé J., Ziad A., Fantéi-Caujolle Y., Aristidi E., Renaud C., Blary F., Marjani M.
The Calern atmospheric turbulence station
SPIE conf 9906 on Astronomical telescopes + instrumentation Edinburgh, 26 June - 1 July 2016
Abstract :
From its long expertise in Atmospheric Optics, the Observatoire de la Cote d'Azur and the J.L. Lagrange Laboratory have equipped the Calern Observatory with a station of atmospheric turbulence measurement (CATS: Calern Atmospheric Turbulence Station). The CATS station is equipped with a set of complementary instruments for monitoring atmospheric turbulence parameters. These new-generation instruments are autonomous within original techniques for measuring optical turbulence since the first meters above the ground to the borders of the atmosphere. The CATS station is also a support for our training activities as part of our Masters IMAG2E and OPTICS, through the organization of on-sky practical works.
79. Crouzet N., Mékarnia D., Guillot T., Abe L., Agabi A., Rivet JP., Gonçalves I., Schmider F.X., Daban J.B., Fantéi-Caujolle Y., Gouvret C., Fruth T., Barbieri M., Bayliss D., Zhou G., Aristidi E., Szulagyi J., Erikson A., Rauer H., Bondoux E., Challita Z., Fressin F., Valbousquet F., Bonhomme S., Bouchy F., Gerakis J., Bouchez G.
Six winters of photometry from Dome C, Antarctica: challenges, improvements, and results from the ASTEP experiment
SPIE conf 9908 on Astronomical telescopes + instrumentation Edinburgh, 26 June - 1 July 2016
Abstract :
ASTEP (Antarctica Search for Transiting ExoPlanets) is a pilot project that aims at searching and characterizing transiting exoplanets from Dome C in Antarctica and to qualify this site for photometry in the visible. Two instruments were installed at Dome C and ran during the winters between 2008 and 2013. The analysis of the collected data is nearly complete. In this paper, we present the technical challenges, solutions, and limitations of these instruments in light of the quality of the extracted lightcurves. We detail issues and improvements made over the years and their impact on the operations and data quality. Overall, results from the ASTEP experiment will serve as a basis to design and operate future optical and near infrared telescopes in Antarctica.
78. Chadid M., Vernin J., Abe L., Agabi A., Liu L.Y., Yao Y., Aristidi E.
Opening a new window on the southern stars for less money: PAIX the first Antarctica polar mission photometer
SPIE conf 9908 on Astronomical telescopes + instrumentation Edinburgh, 26 June - 1 July 2016
Abstract :
In this talk, we describe the first polar mission PAIX -Photometer AntarctIca eXtinction- and the first outcome of stellar pulsation from the heart Antarctica during 1 polar night. We briefly discuss our new results and perspectives on the polar instrumentation development and stellar evolution from Antarctica, especially the connection between temporal hydrodynamic phenomena and cyclic modulations and how PAIX challenges space telescopes and even has more advantages in observing in UBVRI bands and then collecting multicolor photometric measurements. Finally, we highlight the impact of PAIX -the robotic Antarctica photometer- on the stellar pulsation and evolution study.
77. Moretto G., Abe L., Aristidi E., Carbillet M., Epchtein N., Vakili F., Ziad A., Langlois M., Vauglin I.
How to capitalize the unique Antarctica site performance for astronomy
Astronomy and Astrophysics from Antarctica, Third Workshop of the SCAR AAA
7-10 August 2015, Kilauea Military Camp, Hawaii
76. Moretto G., Agabi A., Aristidi E., Carbillet M., Chadid M., Fossat E., Guillot T., Vernin J., Ziad A.
Antarctica Dome C astronomy activities update (2015)
Astronomy and Astrophysics from Antarctica, Third Workshop of the SCAR AAA
7-10 August 2015, Kilauea Military Camp, Hawaii
Post-adaptive optics bispectral speckle imaging
AO data processing workshop, Marseille, 26-27 May 2015
Abstract :
Adaptive Optics (AO) in the visible is more difficult with respect to near-infrared because of
degraded spatial and temporal coherence of the turbulent atmosphere. Images are less corrected and
generally contain a large amount of speckle residuals. Dedicated
image processing techniques become necessary to reach the telescope theoretical
resolution. We propose to apply the ''Speckle Masking'' method to post-AO
partially corrected images to reconstruct objects at the
diffraction limit of the telescope. We present here first results based
on numerical simulation of binary stars, using the ''Building Block''
Post-adaptive optics speckle imaging in the visible
ESO HIRES 2014: Astronomy at high angular resolution - a cross-disciplinary approach
, Garching, 24-28 November 2014
Abstract :
In the visible domain, turbulence is very fast and strong, and adaptive optics (AO) systems cannot provide full correction. In this context one can wonder whether deconvolution techniques are still that relevant, or whether it would be more interesting to work directly on short-exposure images by means of speckle methods used on partially corrected images. The purpose of this work is hence to make a first comparison, by means of numerical simulations of binary star post-AO images, between: (i) deconvolution methods applied to a long-exposure image, and (ii) speckle methods applied to a set of short-exposure images.
73. Carbillet M., La Camera A., Deguignet J., Prato M., Bertero M., Aristidi E., Boccacci P.,
Strehl-constrained reconstruction of post-adaptive optics data and the Software Package AIRY, v. 6.1
SPIE conf 9145 on Astronomical telescopes + instrumentation Montreal, 22-27 June 2014
Abstract :
We first briefly present the last version of the Software Package AIRY, version 6.1, a CAOS-based tool which includes various deconvolution methods, accelerations, regularizations, super-resolution, boundary effects reduction, point-spread function extraction/extrapolation, stopping rules, and constraints in the case of iterative blind deconvolution (IBD). Then, we focus on a new formulation of our Strehl-constrained IBD, here quantitatively compared to the original formulation for simulated near-infrared data of an 8-m class telescope equiped with adaptive optics (AO), showing their equivalence. Next, we extend the application of the original method to the visible domain with simulated data of an AO-equiped 1.5-m telescope, testing also the robustness of the method with respect to the Strehl ratio estimation.
72. Blary F., Ziad A., Borgnino J., Fantei-Caujolle Y., Aristidi E., Lantéri H.
Monitoring atmospheric turbulence profiles with high vertical
resolution using PML/PBL instrument
SPIE conf 9145 on Astronomical telescopes + instrumentation Montreal, 22-27 June 2014
Abstract :
Wide-Field Adaptive Optics (WFAO) new concepts for adaptive optics (AO) improvement have been proposed
for the next generation of telescopes. In order to be efficient, correction using WFAO require knowledge of
atmospheric turbulence parameters. The structure constant of index-of-refraction fluctuations (CN2)
being one
of them, indirect methods implemented in MASS, SLODAR, CO-SLIDAR and MOSP instrument have been
proposed to measure CN2(h) profile through different layers of the atmosphere. A new monitor called the Profiler
of Moon Limb (PML) is presented. In this instrument, CN2(h) profiles are retrieved from the transverse covariance via minimization of a maximum likelihood criterion under positivity constraint using an iterative gradient
method. An other approach using a maximum a posteriori (MAP)/Expectation Maximization (EM) algorithm is
also studied. Instrument errors are mainly related to the detection of the Moon limb position and are mostly due
to photon noise. Numerical simulations are used to evaluate the error on the extracted profile and its propagation
in the inverse technique.
Abstract :
We present first results of a new instrument, the Generalized Differential Image Motion Monitor (GDIMM), aiming at monitoring parameters of the optical turbulence (seeing, isoplanatic angle, coherence time and outer scale). GDIMM is based on a small telescope equipped with a 3-holes mask at its entrance pupil. The seeing is measured by the classical DIMM technique using two sub-pupils of the mask (6~cm diameter separated by a distance of 20~cm), the isoplanatic angle is estimated from scintillation through the third sub-pupil (its diameter is 10~cm, with a central obstruction of 4~cm). The coherence time is deduced from the temporal structure function of the angle of arrival (AA) fluctuations, thanks to the high-speed sampling rate of the camera. And the difference of the motion variances from sub-apertures of different diameters makes it possible to estimate the outer scale. GDIMM is a compact and portable instrument, and can be remotely controlled by an operator. We show in this paper the first results of test campaigns obtained in 2013 and 2014 at Nice observatory and the Plateau de Calern (France). Comparison with simultaneous data obtained with the Generalized Seeing Monitor (GSM) are also presented.
70. Rivet J.P., Vernet D., Scardia M., Prieur J.L., Bendjoya P., Suarez O., Abe L., Pansecchi L., Argyle B., Aristidi E.,Koechlin L.
The current status of PISCO at Calern
Workshop on Automation and Robotic Operation of Moderate-Sized Telescopes for Speckle Interferometry, U.S. Naval Observatory, Washington, DC, USA 2-3 June 2014
Abstract :
The futures large telescopes will be certainly equipped with Multi-Conjugate Adaptive Optics systems. The optimization of the performances of these techniques requires a precise specification of the different components of these systems. Major of these technical specifications are related to the atmospheric turbulence particularly the structure constante of the refractive index Cn2(h) and the outer scale L0(h). New techniques based on the moon limb observation for the monitoring of the Cn2(h) and L0(h) profiles with high vertical resolution will be presented. A new monitor PBL (Profileur Bord Lunaire) for the extraction of the Cn2(h) profile with high vertical resolution has been developed. This instrument uses an optical method based on observation of the moon limb with a DIMM configuration (Differential Image Motion Monitor). Indeed, in the PBL the lunar limb is observed through two sub-apertures of 6cm separated by a base of ~30cm. The moon limb offers a continuum of stars at different angular separations allowing the scan the atmosphere with a very high resolution. The angular correlation along the lunar limb between of the differential distance between the two images of the lunar edge leads to the Cn2(h) profile. The other parameters of turbulence are also accessible from this instrument as the profile of outer scale, the seeing and isoplanatic & isopistonicdomains. The PBL succeeded to our first moon limb profiler MOSP (Monitor of Outer Scale Profile) which was developed mainly for outer scale profile extraction. Several campaigns have been carried out with MOSP particularly at Mauna Kea Observatory (Hawaii) and Cerro Paranal in Chile. The PBL instrument has been installed at Dome C in Antarctica since January 2011. In addition to this winterized PBL for Dome C, a second copy of this instrument has been developed for mid-latitude sites. A first campaign with this light version of PBL, was carried out at the South African Large Telescope (SALT) Observatory in August 2011.
68. Vauglin I., Langlois M., Moretto G., Epchtein N., Aristidi E., Carbillet M., Abe L.
A New Generation of Infrared Sky Survey for the E-ELT era Proc. SF2A-2013, p.37-39 (2013),
Abstract :
A New Generation Infrared Sky Survey (ANGISS) is proposed for the next decade offering performances matching the requests of the new extremely large telescopes such as the E-ELT in order to prepare and follow-up their programmes. This will require the coverage of thousands of square degrees at K=25 or better, with an angular resolution of 300 mas and time domain exploration. Set up on the Antarctic Plateau, a NGISS using a relatively modest telescope (2.5 to 4 m) looks particularly attractive. Moreover, an off-axis optical combination is preferred to fully benefit from the exceptional atmospheric properties of the site and to explore the 2.3-4 micron window in optimal thermal emission conditions.
67. Epchtein N., Moretto G., Langlois M., Vauglin I., Abe L., Carbillet M., Aristidi E.
New Generation Near Infrared Surveys for the E-ELT era ESO Conf. EELT 2013 - Shaping E-ELT Science and Instrumentation
, 25 Feb--1 Mar 2013
Abstract :
The Extremely Large Telescopes will require a new generation of large
scale or even all-sky surveys much deeper than those presently
available. The LSST will probably provide an appropriate answer for the
optical range, but few projects have been proposed in the near
infrared, so far. I''ll briefly review the existing projects in that
respect with a special emphasis on a possible settlement of a survey
facility on the Antarctic continent.
66. Petenko I., Aristidi E., Agabi K., Bouchez G.
Bondoux E., Pietroni I., Argentini S., Viola A.,
Casasanta G., Mastrantonio G.
Influence of the optically active turbulence on astronomical seeing at Concordia station, Dome C, Antarctica EGU General Assembly, Vienna, 7--12 April 2013
Abstract :
The study of the distorting action of the atmospheric turbulence is
important to understand the reason of the astronomical seeing
variability, and to propose reliable methods to estimate the seeing
quality. The influence of the atmospheric surface layer thermal
turbulence on distortion of astronomical images is investigated. During
a campaign carried out at Concordia station at Dome C, East Antarctica
in winter 2012, an experiment was carried out to determine the behaviour
and the contribution of the optically-active atmospheric turbulence in
the lowest tens meters. The surface layer in the interior of Antarctica
during winter is extremely stably stratified with the difference of
temperature between the surface and the top of the inversion reaching
30-40 °C. Direct optical measurements of the seeing made by
differential image motion monitors (DIMM) at two levels, 8 and 20 m,
were made simultaneously with turbulence observations in the
near-surface atmospheric layer. The intensity of the thermal turbulence
was detected and evaluated using both a specially designed
high-resolution sodar, and sonic anemometer measurements. The statistics
of some meteorological variables, including long-wave downwelling
radiation, characterising the presence of cloudiness are obtained.
Typical patterns of the turbulence shown by sodargrams are analysed and
classified. The statistics of the heights of the surface-based turbulent
layer and of the seeing quality values are presented. A correlation
exists between the seeing quality and the intensity of turbulence
measured by sodar. Statistics of turbulent optical factor (TOF) for
different layers within the surface layer are analysed for the total
period and for clear sky conditions to give recommendations on how to
choose an optimal height for the installation of the astronomical
instrumentation.
65. Aime C., Aristidi E., Rabbia Y.
The Fresnel
diffraction: a story of light and darkness. EAS Pub. Series, 2012, 59, 37 (2013)
Abstract :
In a first part of the paper we give a simple introduction to the free
space propagation of light at the level of a Master degree in Physics.
The presentation promotes linear filtering aspects at the expense of
fundamental physics. Following the Huygens-Fresnel approach, the
propagation of the wave writes as a convolution relationship, the
impulse response being a quadratic phase term. We give its
corresponding filter in the Fourier plane. As an illustration, we show
how a periodic structure propagates at various distances, introduce
lenses as quadratic phase terms, discuss their Fourier transform
properties and give some properties of Soret screens. Classical
diffractions of rectangular figures are also given there. In a second
part of the paper, the presentation turns onto the use of external
occulters in coronagraphy for the detection of exoplanets and the study
of the solar corona. There we look to the shadows produced by the
screens. Making use of Lommel series expansions, we obtain the
analytical expression for the diffraction of a circular screen, thereby
giving the complete formalism for the Arago-Poisson spot. The paper
ends with a brief presentation of shaped occulters.
Abstract :
We present long term site testing statistics obtained at Dome C,
Antarctica with various experiments deployed within the Astroconcordia
programme since 2003. We give values of integrated turbulence
parameters in the visible at ground level and above the surface layer,
vertical profiles of the structure constant Cn^2 and a statistics of
the thickness of the turbulent surface layer.
63. Aristidi E., Agabi A., Fossat E., Ziad A., Abe L., Bondoux
E., Bouchez G., Challita Z., Jeanneaux F., Mékarnia D., Petermann D.,
Pouzenc C.
Dome C site
testing: long term statistics of integrated optical turbulence
parameters at ground level. IAU Symposium 288
Astrophysics from Antarctica, Beijing, 20-24 August 2012
Abstract :
We present long term site testing statistics based on DIMM and GSM data
obtained at Dome C, Antarctica. These data have been collected on the
bright star Canopus since the end of 2003. We give values of the
integrated turbulence parameters in the visible (wavelength 500 nm).
The median value we obtained for the seeing are 1.2 arcsec, 2.0 arcsec
and 0.8 arcsec at respective elevations of 8m, 3m and 20m above the
ground. The isoplanatic angle median value is 4.0 arcsec and the median
outer scale is 7.5m. We found that both the seeing and the isoplanatic
angle exhibit a strong dependence with the season (the seeing is larger
in winter while the isoplanatic angle is smaller).
62. Abe L., Rivet J.P., Agabi A., Aristidi E., Mékarnia D.,
Goncalves I., Guillot T., Barbieri M., Crouzet N., Fressin F., Schmider
F.X., Fantei-Caujolle Y., Daban J.B., Gouvret C., Peron S., Petit P.Y.,
Robini A., Dugué M., Bondoux E.
Two years of
polar winter observations with the ASTEP400 telescope SPIE - Astronomical
telescopes and instrumentation, Amsterdam, 1-6 July 2012
Abstract :
The ASTEP program is dedicated to
exo-planet transit search from the Concordia Station located at Dome
C, Antarctica. It comprises two instruments: a fixed 10cm refractor
pointed toward the celestial South Pole, and a 400mm Newton telescope
with a 1×1 degree field of view. This work focuses on the latter
instrument. It has been installed in November 2009, and has been
observing since then during the two polar winters 2010 and 2011.
After presenting the main science observing programs, we review the
telescope installation, performance, and describe its operating
conditions as well as the data reduction and handling strategy. The
resulting lightcurves are of unprecedented quality for a ground-based
telescope of that size, comparable with a 1-m class telescope located
at a tempered site.
61. Argentini S., Petenko
I., Viola A., Mastrantonio G.,
Pietroni I., Casasanta G., Aristidi E., Genthon C., Conidi A.
Thermal
structure of the boundary layer over the snow: results from an under
way experimental field at
CONCORDIA station, Dome C, Antarctica 16th
International Symposium for the Advancement of Boundary-Layer Remote
Sensing – ISARS 2012, 5-8 June 2012,
Boulder, Colorado, USA
(2012)
Abstract :
A field experiment was launched at the French - Italian station of
Concordia at Dome C, east Antarctic Plateau,
on December 2011. The main objective of the experiment is to monitor
the fine structure of the atmospheric surface layer in order to
determine the space/time scales of the turbulent processes under very
stable conditions. We also want to study the processes which lead to
the formation of the warming events observed periodically during the
winter. The
experiment will last until January 2013. The measurements are made with
a surface layer mini-sodar
(SLM-sodar) and a sonic anemometer. The radiation budget and heat flux
measurements into the snow are
also provided. To ensure vertical extensions and resolutions suitable
to the study of both processes, the
SLM-sodar is set to operate in a configuration that allows to switch
from high resolution surface layer
observations (carrier frequency: 4850 Hz; pulse repetition time: 2 s;
range: 2 - 300 m) to long range
operation (carrier frequency: 2000 Hz; pulse repetition time: 6 s;
range: 15 - 900 m). A few results of the first
two months of measurements are presented together with the experimental
strategy planned for the winter.
60. Genthon C., Six D., Traullé O. Aristidi E.
Two years of atmospheric boundary layer tower
observation at Dome C, Antarctic plateau XXVth International
Union of Geodesy and Geophysics General Assembly , IUGG,
Melbourne, Australie, June 28 - July 7, 2011
Abstract :
The
lower atmospheric boundary layer at Dome C, on the Antarctic plateau
((75°06' S, 123°20' E, 3233 m a.s.l.) is monitored since January 2008
(Genthon et al., J. Geophys. Res.,2010). Anemometers, thermometers and
hygrometers were deployed at 6 levels above the surface to ~43 m. Harsh
local conditions (extreme cold temperatures, frost deposition) have
affected the operation of the instruments. Several failed in the winter
of 2008 but improvements since have allowed essentially
continuous records with limited interruptions since 2009. Cases of
thermal convective mixing (adiabatic temperature profile, in summer) as
well as cases of very strong inversions (more than 2°C per meter
locally, in winter) were recorded. The mean winter (MJJA) temperature
is 7°C (3°C) warmer at the lowest (resp. highest) observation level in
2009 than in 2010. The reports from the Antarctic Meteorological
Research Center automatic weather station at Dome C indicate that the 2
winters are the warmest and coldest (resp) on record over the past
decade. This allows characterizing and contrasting “warm” and “cold'
winter boundary layers on the Antarctic plateau, as several occurrences
of winter “warm events” have occurred in 2009 whereas surface
temperatures have dropped below -80°C in 2010. Operating and processing
sonic anemometers and thermometers was particularly difficult but
should provide direct measures of turbulence parameters within those
extreme boundary layers. Turbulent fluxes computation were tested
following “AmeriFlux” protocols (cleaning high-pass filtering,
despiking, double-rotation, etc). Validating
evaluations of turbulence in such particular conditions is not
straightforward though.
59. Allouche F., Glindemann A., Aristidi E., Vakili F.
APIC : Absolute Position Interfero Coronagraph for direct exoplanet detection: first laboratory results
SPIE 7735, 267 (2010)
Abstract :
For the detection and direct imaging of exoplanets, when the intensity
ratio between a star and its orbiting planet can largely exceed 106,
coronagraphic methods are mandatory. In 1996, a concept of achromatic
interferocoronagraph (AIC) was presented by J. Gay and Y. Rabbia for the
detection of very faint stellar companions, such as exoplanets. In an
earlier paper, we presented a modified version of the AIC permitting to
determine the relative position of these faint companions with respect
to the parent star, a problem unsolved in the original design of the
AIC. Our modification lied in the use of cylindrical lens doublets as
field rotator. By placing two of them in one arm of the interferometric
set-up of AIC, we destroyed the axis of symmetry induced by the AIC's
original design. Our theoretical study, along with the numerical
computations, presented then, and the preliminary test bench results
aiming at validating the cylindrical lens doublet field rotation
capability, presented in this paper, show that the axis of symmetry is
destroyed when one of the cylindrical doublets is rotated around the
optic axis.
58. Briot D., Arnold L., Jacquemoud S., Schneider J.,
Agabi K., Aristidi E., Berthier J., Bondoux E.,
Challita Z., Petermann D., Pouzenc C., Rocher P.
The LUCAS program: detecting vegetation and traces of life in the Earthshine
Highlights of Astronomy, 15, 625 (2010)
Abstract :
The aim of the LUCAS program is to observe chlorophyll and atmospheric
molecules in the Earthshine spectrum in order to prepare the detection
of life in terrestrial extrasolar planets to be discovered. Actually,
observations from Antarctica offer a unique possibility to study the
variations of Earthshine spectrum during Earth rotation while various
parts of Earth are facing the Moon. Special instrumentation for the
LUCAS program was designed and put in the Concordia station in the Dome
C. Observations are in progress.
57. Robbe-Dubois S., Bresson Y., Aristidi E., Lagarde S.,
Antonelli P., Lopez B., Petrov R.
Fresnel
diffraction in an interferometer : application to MATISSE
SPIE, 7734,
124 (2010)
Abstract :
While doing optical study in an instrument similar to the
interferometers dedicated to the Very Large Telescope (VLT), we have to
take care of the pupil and focus conjugations. Modules with artificial
sources are designed to simulate the stellar beams, in terms of
collimation and pupil location. They constitute alignment and
calibration tools. In this paper, we present such a module in which the
pupil mask is not located in a collimated beam thus introducing Fresnel
diffraction. We study the instrumental contrast taking into account the
spatial coherence of the source, and the pupil diffraction. The
considered example is MATISSE, but this study can apply to any other
instrument concerned with Fresnel diffraction.
56. Briot D., Arnold L., Jacquemoud S., Schneider J.,
Agabi A., Aristidi E., Berthier J., Bondoux E.,
Challita Z., Petermann D., Pouzenc C., Rocher P.
The LUCAS experiment: spectroscopy of Earthshine in Antarctica for detection of life
EAS Pub. Series, 40, 361 (2010)
Abstract :
So as to prepare future observations of terrestrial extrasolar planets
liable to shelter life, we attempt to detect the life on the Earth seen
as a dot. We use the Moon Earthshine, in which any place reflects the
totality of the enlightened part of Earth facing the Moon. Observing
from OHP and from ESO, we detected terrestrial chlorophyll in the near
infrared, the so-called Vegetation Red Edge, and this detection is
larger when forests are present than when an ocean is mainly visible from the Moon. Only if observations are
made from a high latitude location, and at some moments in the year,
Earthshine can be observed during a large part of the day. During these
long observing windows, different “landscapes" are facing the
Moon. So the Earthshine corresponding to various parts of our Earth
could be studied. Preliminary testing observations have been made at
Concordia since the first winterover campaign and the LUCAS experiment has been set up.
55. Carbillet M., Maire A.-L., Le Roux B., Aristidi E.,
Giordano C., Pasqueron de Fommervault O., Gautier J.,
Trinquet H
Adaptive optics (AO) and ground-layer AO for Dome C: numerical simulation results
EAS Pub. Series, 40, 157 (2010)
Abstract : We present the latest results of our on-going closed-loop
“end-to-end” numerical adaptive optics (AO) simulations
concerning both a standard-AO and a three-star ground-layer AO system
for a near-infrared 2-m class telescope at Dome C, Antarctica. We
demonstrate that Dome C is an ideal site for wide-field AO-aided
astronomy, define in details the AO system(s) optimized for the median
turbulence profile considered, and finally show that a 0.3 Strehl ratio
and 200-mas-wide stable point-spread function is reached in band J on at
least a 15'-diameter field.
54. Travouillon T., Aristidi E., Fossat E., Bondoux E.,
Challita Z., Mekarnia D., Jeanneaux F., Odoardi D., Lawrence J. S.
Studying the vertical extent of the ground layer turbulence using sonic anemometers
EAS Pub. Series, 40, 115 (2010)
Abstract : The optical turbulence above Dome C in winter is mainly concentrated in
the first tens of meters above the ground. The properties of this
so-called surface layer were investigated during the last two winterover
by a set of sonics anemometers placed on a 45 m high tower. These
anemometers provide measurements of the temperature and the wind speed
vector. The sampling rate of 10 Hz allows to derivate the refractive
index structure constant C_n^2. We report here the first analysis of
these data.
53. Fossat E., Aristidi E., Astroconcordia Team.
Dome C boundary layer and seeing peculiarities
EAS Pub. Series, 40, 73 (2010)
Abstract : This paper presents some statistical information about the Concordia
turbulent surface inversion layer, regarding height and turbulent
energy, its contribution to the peculiar local seeing, and the free
atmosphere seeing encountered just above this surface layer.
52. Ziad A., Aristidi E., Agabi A., Fossat E.; Borgnino J.; Maire J.; Martin F.
Implication of turbulence optical parameters on HAR techniques at Dome C
EAS Pub. Series, 40, 21 (2010)
Abstract : The HAR observing methods such as Adaptive Optics and Interferometery,
require a better understanding of the behavior of the perturbed
wavefronts, more exactly a better knowledge of the atmospheric
turbulence model in addition to the associate parameters. This is very
crucial for modeling the HAR techniques and particularly for the
evaluation of their performance. Indeed, it is well-known that the
performance of an AO system depends upon the seeing conditions, the
outer scale, the isoplanatic angle and the coherence time. A review of
the site-testing instruments deployed at Dome C will be given, their
pertinence and their implications on HAR techniques will be discussed
comparatively to the Paranal site.
51. Moore A., Allen G., Aristidi E., Ashley M., Bedding T.,
Beichman C., Briguglio R., Busso M., Candidi M., Ciardi D., Cui
X., Cutispoto G., Distefano E., Espy P., Everett J., Feng L., Hu J.,
Jiang Z., Kenyon D., Kulesa C., Lawrence J., Le Roux B., Leslie T., Li
Y., Luong-Van D., Phillips A., Qin W., Ragazzoni R., Riddle R.,
Sabbatini L., Salinari P., Saunders W., Shang Z., Stello D., Storey J.,
Sun B., Suntzeff N., Taylor M., Tosti G., Tothill N., Travouillon T.,
Van Belle G., Von Braun K., Wang L., Yan J., Yang H., Yuan X., Zhu Z.,
and Zhou X .
GATTINI: A
MULTISITE CAMPAIGN FOR THE MEASUREMENTS OF SKY BRIGHTNESS
IN ANTARCTICA
SPIE, 7012,
76 (2008)
Abstract :
We present the Gattini project: a multisite campaign to measure the
optical sky properties above the two high altitude Antarctic
astronomical sites of Dome C and Dome A. The Gattini-DomeC project,
part of the IRAIT site testing campaign and ongoing since January 2006,
consists of two cameras for the measurement of optical sky brightness,
large area cloud cover and auroral detection above the DomeC site, home
of the French-Italian Concordia station. The cameras are transit in
nature and are virtually identical except for the nature of the lenses.
The cameras have operated successfully throughout the past two
Antarctic winter seasons and here we present the first results obtained
from the returned 2006 dataset. The Gattini-DomeA project will place a
similar site testing facility at the highest point on the Antarctic
plateau, Dome A, with observations commencing in 2008. The project
forms a small part of a much larger venture coordinated by the Polar
Research Institute of China as part of the International Polar Year
whereby an automated site testing facility called PLATO will be
traversed into the DomeA site. The status of this exciting and
ambitious project with regards to the Gattini-DomeA cameras will be
presented.
50. Travouillon T., Aristidi E., Fossat E.,
Lawrence J.
SAMPLING THE
GROUND LAYER OF THE ATMOSPHERE AT DOME C USING FAST SONIC ANEMOMETERS
SPIE, 7012, 147 (2008)
Abstract :
The ground layer turbulence at Dome C is the cause for more than 90% of
the total turbulence column. While the height of this layer has been
currently measured to be approximately 30m, no long term statistics is
available from this part of the atmosphere. In order to plan the
construction of future telescope at this site temperature site,
temperature, wind speed and turbulence measurements are also necessary.
Using fast sonicanemometers we present, a preliminary set of data
covering January to October 2007 sampling these quantities at heights
of 8, 16 and 28 meters..
49. Allouche F., Vakili F., Glindemann A., Aristidi E.,
Abe L., Fossat E., Douet R.
IRAN:
LABORATORY TEST BENCH FOR HYPERTELESCOPE PUPIL-PLANE RECOMBINATION
SPIE, 7013,
117 (2008)
Abstract :
In 2004, our group proposed IRAN, an alternative beam-combination
technique to the so-called hypertelescope imaging method introduced by
Labeyrie in the 1990s. We have recently set up a laboratory experiment
aiming at validating our image densification approach instead of the
pupil densification scheme of Labeyrie. In our experiment, seven
sub-apertures illuminated by laser sources are recombined using the
IRAN scheme. The validation of the IRAN recombination consists
basically in retrieving the point-spread intensity distribution (PSID),
demonstrating the conservation of the object-image convolution
relation. We will introduce IRAN, compare it to the hyper-telescope,
and present the experimental results that we obtained.
48. Trinquet, H; Agabi, A;
Vernin, J;
Azouit, M; Aristidi, E;
Fossat, E
OPTICAL
TURBULENCE AND OUTER SCALES ABOVE DOME C IN ANTARCTICA
SPIE, 7012,
75, (2008)
Abstract :
Dome C in Antarctica is a particular astronomical site when considering
the optical turbulence conditions. From the first winterover campaign
performed in 2005 at Dome C, the set of 34 meteorological balloon
profiles has been analyzed. The meteorological balloons were equipped
with microthermal sensors used to sense the vertical 2 2 profile
of the optical turbulence intensity Cn . The Cn median profile,
mean temperature and mean horizontal 2 wind speed
are given. The Cn median profile is characterized by a very
strong and thin turbulent surface layer. The surface
layer height is defined. The median outer scale profile at Dome C is
computed using the Tatarski definition. The von
Karman outer scale is also deduced. The integrated parameters as Fried
parameter r0 , a a coherence time tau0 , isoplanatic angle theta0 and the
spatial-coherence outer scale L0 used to define astronomical site
quality, are computed
at 8 m above the ground and above the turbulent surface layer.
Keywords: atmospheric effects, interferometry, site testing, outer
scale
47. Moore A. M.; Leslie T.; Ashley M. C. B.;
Aristidi E.; Bedding T.; Briguglio R.; Busso M.; Candidi M.; Cutispoto
G.; Distefano E., Everett, J.; Kenyon, S.; Lawrence, J.;
Le Roux, B.; Luong-van, D.; Phillips, A.;
Ragazzoni, R.; Sabbatini, L.; Salinari, P.;
Stello, D.; Storey, J. W. V.; Taylor, M.;
Tosti, G.; Travouillon, T.
The Dome C Gattini sky brightness cameras: results from the first year of operation
EAS Pub. Series 33, 13, (2008)
Abstract : The Gattini-DomeC project, part of the IRAIT site testing campaign and
ongoing since January 2006, consists of two cameras for the measurement
of optical sky brightness, large area cloud cover, and auroral detection
above the DomeC site, home of the French-Italian Concordia station. The
cameras are transit in nature and are virtually identical except for the
nature of the lenses. The cameras have operated throughout the past two
Antarctic winter seasons and here we present the results obtained from
the 2006 winter-time dataset of the wide field “All-sky camera".
Abstract :
The idea of starting an astronomical site testing in Antarctica began
during a congress organized by French Académie des Sciences, in 1992,
and entitled "Recherches polaires-Une Stratégie pour l'an 2000â€".
At this time, one of us (Vernin 1994) gave a proposal for an
astronomical site testing in Antarctica. This proposal was rapidly
followed by a meeting between Al Harper (from ‘Center for
Astrophysical Research in Antarctica’, Chicago), Peter Gillingham
(from the Anglo Australian Observatory, Australia) and Jean Vernin
(from Nice University) at Lake Geneva, Wisconsin, in 1993. It was
decided to investigate what was the astronomical quality of South Pole
station, each institute bringing its own participation: CARA, the South
Pole infrastructure, University of New South Wales, a PhD student and
Nice University its expertise and instruments.
Abstract :
In the recent years, a lot of instruments have been put into operation
during the polar summer at DomeC., Then, during the first polar night
when the Astro-Concordia sation was open for the first time during
winter, about 40 balloons (Azouit & Vernin) instrumented to measure
optical turbulence profiles and 2 Differencial Image Motion Monitors
(DIMM) were setup. The main results from this first important campaign
are found in Agabi et al. (2006). It appears from this first night time
observations that almost all the optical turbulence was concentrated in
the first 30 m above the ice. At an elevation of 8.5 m above the ice
the seeing is about 1".4, while above an elevation of 30 m the seeing
drops down to 0″.36. This last figure is coherent with the estimation
from Lawrence et al. (2004) if one takes into account that they were
not sensitive to the first 30 m., which corresponds to the turbulent
surface layer.
Abstract :
The next generation (post-VLTI) of multi-telescope interferometric
arrays operated in optical/infrared wavelengths should be kilometric,
from 1 to 10 km. The Concordia station offers a unique opportunity to
set such an interferometer in the best atmospheric conditions presently
known on Earth.
A TEST FOR THE DETECTION OF VEGETATION ON
EXTRASOLAR PLANETS: DETECTION OF VEGETATION IN EARTHSHINE SPECTRUM AND
ITS DIURNAL VARIATIONS
Highlights of Astronomy 14, 711, 2007
Abstract :
The search for life in extraterrestrial planets is to be tested first
with the only planet known to shelter life. If the planet Earth is used
as an example to search for a signature of life, the vegetation is one
of its possible detectable signature, using the Vegetation Red Edge due
to chlorophyll in the near infrared (0.725 microns). We focus on the
test
of the detectability of vegetation in the spectrum of Earth seen as a
simple dot, using the reflection of the global Earth on the lunar
surface, i.e., Earthshine. On the Antartic, the Earthshine can be seen
during several hours in a day (not possible at our latitudes) and so
variations due to different parts of Earth, that is to say oceans and
continents facing the Moon could be detected.
42. Guerri G., Abe L.; Aristidi E.; Daban J. B.;
Rivet J. P.; Bendjoya P.; Vakili F.; Agabi A.
CORONA: FIRST LIGHT AT DOME C OF THE
ANTARCTICA PROTOTYPE APKC CORONOGRAPH EAS Pub. Series 25, 339, 2007
Abstract :
We present the results of the first light of CORONA obtained during the
summer campaign 2005 at Dome C. The CORONA experiment uses an automated
14in antarctized telescope for its remote operation from the Concordia
station. The instrument includes an Achromatized Phase Knife
Coronagraph (APKC) with no tip-tilt correction. The high contrast long
exposure is obtained from image selection among raw short exposures.
41. Sabibekova T., Fossat E.; Vernin J.; Agabi A.; Aristidi
E.; Azouit M.; Chadid M.; Trinquet H.; Genthon C.; Krinner G.; Sarazin
M.
CHOOSING DOME C, ANTARCTIC PLATEAU AS FUTURE
ASTRONOMICAL OBSERVATORY
EAS Pub. Series 25, 69, 2007
Abstract :
In this paper we present year-round climatological analysis made from
radio-sounding measurements and ECMWF Data. And we end up with a
generalized conclusion (scientific aspect) from statistical results of
site-testing at Concordia concerning the feasibility of the future
astronomical exploitation of Dome C.
40. Vernin J.,
Agabi A., Aristidi E., Azouit M., Chadid M.,
Fossat E., Sadibekova T., Trinquet H., Ziad A.
HISTORY, PRESENT
STATUS AND FUTURE OF SITE TESTING AT DOME C
EAS Pub. Series 25, 23, 2007
Abstract : Hereafter we give a brief history of our contribution to astronomical
site testing in Antarctica, at least for the high angular resolution in
the visible range. The decision to undertake the first site testing at
South Pole began one year after a congress organized by French
Académie des Sciences, in year 1992. Indeed, in 1993 a meeting
took place in Chicago with the participation of Peter Gillingham, Al
Harper and Jean Vernin where each one took the respective responsibility
of 1) giving a PhD student, 2) the South Pole infrastructure and 3) the
relevant instruments. During winter 1995, thanks to a mast equipped with
micro-thermal sensors, we demonstrated (Marks et al., 1996, A&AS,
118, 1) that the first 30 m of the surface layer was disrupted by strong
optical turbulence. Then, the year after, 15 balloons equipped with
micro-thermal probes were successfully launched from South Pole. Marks
et al. (1999, A&AS, 134, 161) shown that most of the optical
turbulence at South Pole was concentrated within a layer 200 m thick
above the ice level. From this study, it becomes clear that the
noticeable katabatic wind present at South Pole was generating this huge
surface layer and that is why we oriented our astronomical site
characterization toward Dôme C. Our first summer seeing
estimations began in 2000, which demonstrated (Aristidi et al., 2003,
A&AS, 406, L19 & Aristidi et al., 2005, A&A, 444, 651) that,
as expected, the surface wind was much less than at South Pole, and, as
a matter of fact, the seeing was much better, and was even exceptional
during the four hours of the afternoon where a seeing of less than 0.5
arcsec was measured. In 2005, the Concordia base was first open during
the polar night, and one of us, A. Agabi was able to launch 41 balloons
equipped with micro-thermal sensors. A differential image motion monitor
(DIMM) was also setup with success. At mid winter, Agabi et al. (2006,
PASP, 118, 344) showed that most of the optical turbulence came from the
first 30 m surface layer and very little from the rest of the atmosphere
(1.3 arcsec above 8.5 m and 0.37 arcsec above 30 m).
39. Chadid M., Vernin J., Aristidi E.,
Trinquet H., Azouit M., Sadibekova T.
SINGLE STAR SCIDAR AT DOME C
EAS Pub. Series 25, 63, 2007
Abstract :
Here we present the first light of the Single Star Scidar (SSS) at Dome
C, during January 2005 and the first results obtained during the winter
2006. We recall the SSS principle, how it is designed to resist to very
low temperatures and to be adjusted in a very simple way. No exemple of
long period of observation can be given since the huge amount of data
cannot be sent back to our laboratory to be offline processed, due to
low data transfer available from Dome C. But, a short file is shown,
which demonstrates the major contribution of the surface layer to the
whole atmosphere optical turbulence. Almost 300 hours of observations
have been taken successfully during winter 2006.
38. Moore A., Aristidi E.; Ashley M.; Briguglio R.; Busso M.;
Candidi M.; Everett J.; Kenyon S.; Lawrence J.; Le Roux B.; Luong-van
D.; Phillips A.; Ragazzoni R.; Salinari P.; Storey J.; Taylor M.;
Tosti G.; Travouillon T.
THE GATTINI CAMERAS FOR OPTICAL SKY
BRIGHTNESS MEASUREMENTS AT DOME C, ANTARCTICA
EAS Pub. Series 25, 35, 2007
Abstract :
The Gattini cameras are two site testing instruments for the
measurement of optical sky brightness, large area cloud cover and
auroral detection of the night sky above the high altitude Dome C site
in Antarctica. The cameras have been operating since installation in
January 2006 and are currently at the end of the first Antarctic winter
season. The cameras are transit in nature and are virtually identical,
both adopting Apogee Alta CCD detectors. By taking frequent images of
the night sky we obtain long term cloud cover statistics, measure the
sky background intensity as a function of solar and lunar altitude and
phase and directly measure the spatial extent of bright aurora if
present and when they occur. The full data set will return in December
2006 however a limited amount of data has been transferred via the
Iridium network enabling preliminary data reduction and system
evaluation. An update of the project is presented together with
preliminary results from data taken since commencement of the winter
season.
37. Vernin J., Chadid-Vernin M., Aristidi E.,
Trinquet H., Sadibekova T.
SINGLE STAR SCIDAR FIRST LIGHT FROM DOME C
IAU 26th meeting, special session on
Astronomy in Antarctica. Prague, August 22-23, 2006
Abstract : Here, we present the SSS first light from Dome C Antarctica. Results
obtained during Chadid's expedition in the Summer Season 2005-2006 . The
alpha Car observations are obtained during the day and using a 40 cm
telescope. The SSS "Single Star Scidar" technique derives from the
so-called Scidar (SCIntillation Detection and Ranging) technique, which
analyses the scintillation, on the entrance pupil of a telescope, of a
double star. The scientific goal is to measure vertical profiles of the
Optical Turbulence C_N ^2 (h) and the wind speed *V*(h) at Dome C from
the scintillation of a single star. From those two profiles it is
possible to deduce almost all the parameters which can help to optimize
all the instruments devoted to High Angular Resolution Astronomy, such
as Adaptive Optics and Interferometry. The SSS at Dome C is composed of
a 40 cm telescope driven by an equatorial mount. A short focal lens is
used to collimate the optical beam, and the defocussed image of the
telescope pupil is acquired by a CCD. Several thousands of images are
analyzed in real time to deliver spatio-temporal cross correlations.
Each few tens of seconds, such a correlation is stored in order be
processed off line with the "simulated annealing" method. The
development and construction of this instrument was made possible with
help of: Air Force Office of Scientific Research and the European Office
of Aerospace Research and Development (USA), Programmes Internationaux
de Cooperation Scientifique, INSU and CNRS contracts, a European "ELT
Design Study" contract, the IPEV infrastructure and financing,
AFRL-VSBYA (USA), IAC (Spain) and ANR "CASDOA" contract.
36. Vernin J.,
Agabi A., Aristidi E., Azouit M., Chadid-Vernin M.,
Fossat E., Sadibekova T., Ziad A.
SITE TESTING AT DOME C: HISTORY, PRESENT
STATUS AND FUTURE
IAU 26th meeting, special session on
Astronomy in Antarctica. Prague, August 22-23, 2006
Abstract :
Here we present why we decided to undertake a site characterization at
Dome C, Antarctica following a first step made at South Pole. It was
clear that poor seeing measured at South Pole was mainly due to ground
catabatic wind interacting with strong vertical temperature (refractive
index) gradient. Thus, we though to move to Dome C where no catabatic
wind is expected. We will recall the history of this long adventure.
Then we will present the more recent results which concern daytime
observations as well as nighttime observations, as measured by DIMM,
balloons, GSM and SSS. From this database and the very special vertical
distribution fo the optical turbulence at Dome C, we will present some
strong implications for High Angular Resolution astronomy at Dome C.
35. Briot D.,
Aristidi E., Arnold L., Francois P., Riaud P.,
Rocher P., Schneider J.
A TEST FOR THE DETECTION OF VEGETATION ON
EXTRASOLAR PLANETS: DETECTION VEGETATION IN EARTHSHINE SPECTRUM
IAU 26th meeting, special session on
Astronomy in Antarctica. Prague, August 22-23, 2006
Abstract :
The search for life in extrasolar planets is to be tested first with
the only planet known to shelter life. If the planet Earth is used as
an example to search for a signature of life, the vegetation is one of
its possible detectable signature, using the Vegetation Red Edge due to
chlorophyll in the near infrared (0.725 m). We focus on a test of the
detectability of vegetation in the spectrum of Earth seen as a simple
dot, using the reflection of the global Earth on the lunar surface i.e.
Earthshine. On the Antarctic, the Earthshine can be seen during several
hours in a day (not possible at our latitudes) and so variations due to
different parts of Earth, that is to say oceans and continents, facing
the Moon could be detected.
34. Guerri G., Daban J. B., Vakili F.,
Abe L., Aristidi E., Agabi K., Bendjoya P.,
Sarry J., Schmider F. X., Lopez B.
CORONA: PROGESS REPORT ON THE DOME C
PROTOTYPE APKC CORONOGRAPH
SPIE proc. 6269, 170 (2006)
Abstract :
We outline the concept and laboratory results of our coronagraphic
testbed which has been shipped on automn 2005 to Dome C in Antarctica.
We also describe the principle of our coronagraph achromatization and
the laboratory first data like the coronographic nulling results which
attain more than 103 at least. The future development of our
experiment for a much larger telescope is also outlined. We finally
present CORONA's on-sky first results.
33. Moore A.,
Aristidi, E., Ashley M., Busso M., Candidi M.,
Everett J., Kenyon S., Lawrence J., Luong-Van D.,
Phillips, A., Leroux B., Ragazzoni R., Salinari P., Storey J.,
Taylor M., Tosti G., Travouillon T.
GROUND LAYER TURBULENCE PROFILING USING A
LUNAR SHABAR
SPIE proc. 6269,186 (2006)
Abstract :
Profiling the ground layer turbulence for daytime seeing applications
using an array of photodiodes has been documented in literature, in
particular by Beckers who coined the term "SHABAR" for the instrument,
short for Shadow Band Ranger. In this case the photodiodes measure the
variation of solar intensity as a function of time and the correlation
of scintillation between spatially separated scintillometers can be
used to derive structure constant values for the lower 100m or so. More
recently SHABARs have been applied to night time atmospheric profiling
using the moon as the extended source, such as the Pan-STARRS lunar
SHABAR, a more challenging venture given the lower structure constant
values and therefore higher sensitivity required. We present a summary
of the lunar SHABAR currently operating at the Antarctic site of Dome
C, one of the three Gattini site testing instruments for the
Italian-led IRAIT project. The SHABAR was designed with low noise
performance in mind and for low temperature operation. Ground layer
profiling is of particular importance at the Dome C site during
winter-time as it is known the majority of the integrated seeing
measured at ground level is created in a turbulent layer very close to
the ground.
32. Moore A.,
Aristidi, E., Ashley M., Busso M., Candidi M.,
Everett J., Kenyon S., Lawrence J., Luong-Van D.,
Phillips, A., Leroux B., Ragazzoni R., Salinari P., Storey J.,
Taylor M., Tosti G., Travouillon T.
THE GATTINI CAMERAS FOR OPTICAL SKY
BRIGHTNESS MEASUREMENTS IN ANTARCTICA
SPIE proc. 6267, 53 (2006)
Abstract :
The Gattini cameras are two site testing instruments for the
measurement of optical sky brightness, large area cloud cover and
auroral detection of the night sky above the high altitude Dome C site
in Antarctica. The cameras have been in operation since January 2006.
The cameras are transit in nature and are virtually identical, both
adopting Apogee Alta ccd detectors. The camera called Gattini-SBC
images a 6 degree field centred on the South Pole, an elevation of 75
deg. at the Dome C site. The camera takes repeated images of the same 6
degree field in the Sloan g' band (centred on 477nm) and, by adopting a
lens with sufficiently long focal length, one can integrate the sky
background photons and directly compare to the equivalent values of the
stars within the field. The second camera, called Gattini-allsky,
incorporates a fish-eye lens and images ~110 degree field centred on
local zenith. By taking frequent images of the night sky we will obtain
long term cloud cover statistics, measure the sky background intensity
as a function of solar and lunar altitude and phase and directly
measure the spatial extent of bright aurora if present and when they
occur. An overview of the project is presented together with
preliminary results from data taken since operation of the cameras in
January 2006.
31. Aristidi E.,
Vakili F., Schutz A., Lanteri H., Abe L.,
Belu A., Gori P. M., Lardière O., Lopez B.,
Menut J. L., Patru F.
Abstract :
IRAN is a method of beam-combination in the hypertelescope imaging
technique recently introduced by Labeyrie in optical interferometry. We
propose to observe the interferometric image in the pupil plane,
performing multi-axial pupil plane interferometry. Imaging is performed
in a combined pupil-plane where the point-source intensity distribution
(PSID) tends towards a pseudo Airy disc for a sufficiently large number
of telescopes. The image is concentrated into the limited support of
the output pupil of the individual telescopes, in which the
object-image convolution relation is conserved. Specific deconvolution
algorithms have been developped for IRAN hypertelescope imagery, based
upon Lucy-like iterative techniques. We show that the classical (image
plane) and IRAN (pupil plane) hypertelescope imaging techniques are
equivalent if one uses optical fibers for beam transportation. An
application to the VLT/VIDA concept is presented.
30. Aristidi E., Agabi A., Azouit M., Fossat E., Vernin J.,
Sadibekova T., Ziad A., Martin F.
WINTER SITE TESTING AT DOME C, ANTARCTICA:
FIRST RESULTS
proc. of the JENAM2005, "Distant Worlds":
Technology Roadmap for Future Interferomeric Facilities, p. 171, 4-7
July 2005. Liège
Abstract :
We present site testing results obtained in the night time during the
polar winter at Dome C. These results were collected during the first
Concordia winterover by A. Agabi. They are based upon seeing and
isoplanatic angle monitoring, as well as in-situ balloon measurements
of the refractive index structure constant Cn2(h). The
atmosphere is divided into two regions: (i) a 36 m high surface layer
responsible for 87% of the turbulence and (ii) a very stable free
atmosphere above with a median seeing of 0.36+-0.19 arcsec at an
elevation of h=30 m. The median seeing measured with a DIMM placed on
top of a 8.5 m high tower is 1.3+-0.8 arcsec.
29. Valat B., Lopez B., Schmider F.X., Vakili F., Aristidi E.
PERSPECTIVE OF INTERFEROMETRY IN ANTARCTICA
proc. of the JENAM2005, "Distant Worlds":
Technology Roadmap for Future Interferomeric Facilities, p. 131, 4-7
July 2005. Liège
Abstract :
The recent Dome C site testing shows its potential for interferometry.
This article presents a part of discussion about the site
characteristics measured by E. Aristidi et al. during the polar night.
In Sect. 2 the site characteristics are described. In sect. m the
Mykerinos prototype interferometer is exposed. This instrument can be
the first step before the implementation of future large antarctic
interferometers. It will allow characterizing the best instrument
specifications, test technology in extreme conditions and check the
performances predicted for interferometer from Dome C. Its baseline and
precision will allow studies of hot Jupiters with small apertures.
28. Kellerer A., Agabi A., Aristidi E.,
Coudé Du Foresto V., Sadibekova T., Sarazin M.
INTERFEROMETRIC MEASUREMENTS AT DOME C,
ANTARCTICA
SF2A-2005: Semaine de l'Astrophysique
Francaise, Strasbourg France, June 27-30, 2005.
Abstract :
We have analysed the first interferometric fringes recorded at Dome C,
Antarctica. Measurements were done between 31/01 and 02/02/2005 at
daytime. Aim of the analysis is to measure temporal fluctuations of the
atmospheric piston, which are critical for interferometers and
determine their sensitivity. These scales are derived through the
motion of the image that is formed in the focal plane of a Fizeau
interferometer. Although the coherence time of piston could not be
determined directly due to insufficient temporal and spatial samplings,
a lower limit was nevertheless fixed by studying the decay rate of
correlation between successive fringe recordings. Coherence times are
measured larger than 10 ms, i.e. at least three times higher than the
median coherence time measured at the site of Paranal (3.3 ms).
27. Aristidi E., Agabi A., Fossat E., Travouillon T., Azouit M.,
Vernin J., Ziad A., Martin F., Sadibekova T.
SITE TESTING IN WINTER AT DOME C
SF2A-2005: Semaine de l'Astrophysique
Francaise, Strasbourg France, June 27-30, 2005.
Abstract :
We present site testing results obtained in night-time during the polar
winter at Dome C. These results were collected during the first
Concordia winterover by A. Agabi. They are based upon seeing and
isoplanatic angle monitoring, as well as in-situ balloon measurements
of the refractive index structure constant profiles C_n^2(h).
Atmosphere is divided into two regions: (i) a 36m high surface
layer responsible of 87% of the turbulence and (ii) a very stable free
atmosphere above with a median seeing of 0.36+-0.19 arcsec at an
elevation of h=30m. The median seeing measured with a DIMM placed on
top of a 8.5m high tower is 1.3+-0.8 arcsec.
26. Aristidi E., Agabi A., Azouit M., Fossat E., Martin F.,
Sadibekova T., Vernin J., Ziad A., Travouillon T.
SITE TESTING AT DOME C : SUMMER AND FIRST
WINTER RESULTS FROM THE CONCORDIASTRO PROGRAMME
Conf. on "Wide Field Survey Telecopes on Dome
C/A, Antarctica", Beijing, China, June 3-4, 2005.
Abstract :
We report site testing results obtained in summer and winter at Dome C.
They consist in seeing and isoplanatic angle monitoring, as well as
in-situ balloon measurements of the refractive index structure constant
profiles C_n^2(h). Summer results are based on data taken during two
3-month summer campaings in 2003-2004 and 2004-2005. Winter data were
collected during the first Concordia winterover by A. Agabi. Optical
turbulence appear to be very small in summer, with a median seeing of
0.54 arcsec in the visible, and a median isoplanatic angle of 6.8
arcsec. In winter the amosphere presents a 37 m high turbulent surface
layer. The median seeing measured with a DIMM placed on top of a 8.5 m
high tower is 1.2+-0.7 arcsec. Above this surface layer, at elevation
h=30~m the median seeing is very small: 0.36+-0.18 arcsec.
Abstract :
We present results of site testing at Dome C in summer 2003. Daytime
seeing has been monitored with a DIMM on the bright star Canopus during
the whole campaign, giving average values around 0.8 arcsec. Best
seeing values (below 0.2 arcsec) was obtained at the very beginning of
the campaign in November 2003. First isoplanatic angle measurements,
based on stellar scintillation, were also performed during January,
2004, and are presented in this paper.
Abstract :
We present wind and temperature profiles at Dome C measured by balloon
born weather sonds during the polar summer. Data from 197 flights have
been processed for 4 summer campaigns (200-2001, 2001-2002, 2002-2003
an 2003-3004). We show the exceptionnal wind conditions at dome C in
summer. Average ground wind speed is 3.6 m/s and strongest winds (13
m/s) are observed in the tropopause. We noticed in mid-november the
presence of high altitude strong winds (40 m/s) probably due to the
polar vortex which disappear in summer. These strong winds seem to have
no effect on seeing measurements made with a DIMM at the same period.
Temperature profiles exhibit a minimum at height 5500m (over the snow
surface) that defines the tropopause. Surface layer temperature profile
is classical, with negative gradient in the first 50m above ground in
the afternoon and a strong inversion layer (5 deg.C over 50m) around
midnight. Temperature profile in the 200 first meters becomes almost
flat around 10h and 17h where DIMM measurements have shown very low
turbulence on stellar images. Wind profiles are compared with other
astronomical sites, and with a meteorological model from Meteo
France.
23. Vakili F., Aristidi E., Fossat E., Abe L., Agabi A., Vernin
J., Belu A., Daban J.B., Hertmanni W., Schmider F.X., Maillard A.,
Assus P., Coudé du Foresto V., Swain M.
KEOPS : towards exo-Earths from Dome C of
Antarctica
EAS pub. series 14, 211, 2005.
Abstract :
In this presentation I describe a deployable large optical
interferometer with kilometric baselines targetting the primary goal of
a systematic survey for all F,G, K and M spectral type stars for
detecting their planetary companions. KEOPS is made of 1.5m off-axis
telescopes arranged in concentric rings of 6, 12 and 18 spread over 1
km baselines at maximum. The fast afocal Cassegrain-Coudé optics of
these telescopes are hosted in compact alt-alt mounts optimized for
shipping to Antarctica and their interferometric use: minimum number of
reflecting optics and IR thermal emission. The beams are transported in
burried tunnels to minimize horizontal seeing effects. Sideral OPDs are
corrected via long track delay-lines including switchable offsets to
enable continuous observations of several months during the polar
nights. The highly automated telescopes, beam-collector and the
interferometric focal combiner will be briefly described as well as the
nulling technique applied to detecting the planetray companions at
various separations and contrasts. In addition 100microarcs resolutions
in
the optical IR wavelengths provide KEOPS with unprecedent imaging
capablities which, added to the excellent seeing condtitions of Dome C,
open new windows to probing stellar surface structures, spectro-imaging
of central engines of AGNs in the local group and spatially resolving
micro-lensed events. It is argued that with a reasonnable budget
starting
from R&D for Antarctica technology we may expect KEOPS to become
operational around 2015 much before the zero-risk DARWIN and/or TPF
missions would be launched by space agencies.
22. Aristidi, E., Vakili F., Abe, L. Belu A.,
Lopez, B., Lantéri H., Schutz A., Menut J.L.
Abstract :
This paper describes a method of beam-combination in the so-called
hypertelescope imaging technique recently introduced by Labeyrie in
optical interferometry. The method we propose is an alternative to the
Michelson pupil reconfiguration that suffers from the loss of the
classical object-image convolution relation. From elementary theory of
Fourier optics we demonstrate that this problem can be solved by
observing in a combined pupil plane instead of an image plane. The
point-source intensity distribution (PSID) of this interferometric
``image''
tends towards a pseudo Airy disc (similar to that of a giant monolithic
telescope) for a sufficiently large number of telescopes. Our method is
applicable to snap-shot imaging of extended sources with a field
comparable to the Airy pattern of single telescopes operated in a
co-phased multi-aperture interferometric array. It thus allows to apply
conveniently pupil plane coronagraphy. Our technique called
Interferometric Remapped Array Nulling (IRAN) is particularly suitable
for high dynamic imaging of extra-solar planetary companions,
circumstellar nebulosities or extra-galactic objects where long
baseline interferometry would closely probe the central regions of AGNs
for instance.
21. Vakili F., Belu A., Aristidi E., Fossat E., Maillard A., Abe
L., Agabi A., Vernin J., Daban JB, Hertmanni W., Schmider FX, Assus P.,
Coudé du Foresto V., Swain M.
KEOPS : Kiloparsec Explorer for Optical
Planet Search, a direct-imaging optical array at Dome C, Antarctica
SPIE proc 5491, 1580, 2004.
Abstract :
Recent site seeing testing campaigns conducted by our team from
University of Nice show that Dome C represents the best site on Earth
for astronomical high angular resolution (HAR) observations at optical
and IR wavelengths. The dramatic gain over relevant HAR parameters r0,
L0, theta0 and tau0, added to very low temperatures during the polar
winter nights (-70 deg.C), the dry atmosphere and the possibility of
continuous observations during several nights make Dome C the ideal
site for deploying a kilometric optical interferometer before the 2015
horizon. Here we describe the concept of Kiloparsec Explorer for
Optical Planet Search (KEOPS) that is studied by our group at LUAN.
KEOPS is an interferometric array of 36 off-axis telescopes, each 1.5m
in diameter. Its kilometric baselines open sub-mas snap-shot imaging
possibilities to detect and characterize extra-solar planetary systems,
especially exo-Earths out to 300 parsecs from the visible to the
thermal IR. KEOPS can be considered as a DARWIN/TPF challenger but at a
much lower cost.
20. Abe L., Aristidi E., Vakili F., Domiciano A., Lopez, B.
IMAGING INTERFEROMETRY USING INTERFEROMETRIC
REMAPPED ARRAY NULLING
EAS Publications Series, Volume 12 Astronomy with
High Contrast Imaging , held in Nice, France, 6-10 October, 2003.
Edited by C. Aime and R. Soummer, pp.275-280 (2004)
Abstract :
We present a beam combining technique capable of direct instantaneous
imaging. The particularity is that the image (or PSID, point source
intensity distribution) is formed in a pupil plane. We present the
concept on a theoretical basis, comment on the PSID for on- and
off-axis sources and finally compare it to Fizeau imaging. Future
experiments and reflections about this concept are finally considered.
19. Fossat E., Aristidi E., Agabi A.
THE CONCORDIA STATION ON ANTARCTICA PLATEAU:
THE BEST SITE ON EARTH FOR HIGH ANGULAR RESOLUTION AND HIGH CONTRAST
IMAGING
EAS Publications Series, Volume 12 Astronomy with
High Contrast Imaging , held in Nice, France, 6-10 October, 2003.
Edited by C. Aime and R. Soummer, pp.125-133 (2004)
Abstract :
On the Antarctica plateau, a joint project of french and italian polar
programmes in just near completion: the Concordia station will be open
for winterover operation in 2005. The high altitude and high latitude
of this site, the exceptionally cold, clear and stable atmosphere, the
almost indefinitely flat snow surface and the not so difficult access
make this site the most promising on Earth for future ground based
astronomical projects in various fields, including High Angular
Resolution and High Contrast Imaging.
18. Vakili, F., Aristidi, E., Fossat, E.,
Abe, L.; Lopez, B., Domiciano, A.
KEOPS : AN IMAGING/NULLING LONG BASELINE
INTERFEROMETER AT DOME C
SF2A-2003: Semaine de l'Astrophysique
Francaise, meeting held in Bordeaux, France, June 16-20, 2003. Eds.: F.
Combes, D. Barret and T. Contini. EdP-Sciences, Conference Series, p.
157.
Abstract :
We present our proposal to develop an imaging optical interferometer at
Dome C of Antarctica optimized for both extra-solar planets detection
in the thermal infrared and direct astroseismology of nearby stars. The
science rationale as well as different steps of technological R&D
to make this proposal successful against the adverse conditions of
polar nights will be described.
17. Abe L, Aristidi E., Vakili F.
INTERFEROMETRIC REMAPPED ARRAY NULLING
SF2A-2003: Semaine de l'Astrophysique
Francaise, meeting held in Bordeaux, France, June 16-20, 2003. Eds.: F.
Combes, D. Barret and T. Contini. EdP-Sciences, Conference Series, p.
157.
Abstract :
We present an interferometric beam recombination technique which allows
achromatic and direct true imaging of targets at very high angular
resolution. This technique intrinsically overcomes the main problems of
Labeyrie's hypertelescope design, and can be used in a nulling
configuration. It is thus particularly well suited for high contrast
imaging in the context of exo-planet search and characterization
especially for future space-borne arrays. We present the concept on a
formal basis, and discuss its instrumental implementation.
16. Aristidi E., Agabi A., Vernin J., Azouit M., Martin F., Ziad
A. Fossat E.
FIRST DAYTIME SEEING MONITORING AT DOME C Memorie della
Societa' Astronomica Italiana Suppl., 2, 146,
international workshop on "The
scientific outlook for Astronomy and Astrophysics research at the
Concordia Station", Capri, 28-30 April
2003
Abstract :
The first astronomical seeing monitoring has been made with a DIMM
instrument at the Antarctic plateau site of Dome C in December, 2002 on
the bright star Canopus (alpha Eri) during the daytime. In these far
from optimal conditions, a median seeing of 1.2 arcsec as been
obtained, with extended periods better than 1 arc-sec and 12 percent of
the time better than 0.75 arcsec.
15. Petrov R.G.,Malbet F., Richichi A., Hoffmann K.H., Mourard
D., Agabi K., Antonelli P., Aristidi E., Baffa C., Beckmann U., Berio
P., Bresson P., Cassaing F., Chelli A., Dreiss A., Dugué M., Duvert
G., Forveille T., Fossat E., Gennari S., Geng M., Glentzlin A., Kamm
D., Lagarde S., LeCoarer E., LeContel D., LeContel J.M., Lisi F., Lopez
B., Mars G., Matrinot-Lagarde G., Mekarnia D., Monin J.L., Mouillet D.,
Perrier-Bellet C., Puget P., Rabbia Y., Rebattu S., Reynaud F.,
Robbe-Dubois S., Rousselet-Perraut K., Sacchettini M., Schoeller M.,
Tallon-Bosc I., Weigelt G. C.
AMBER : THE
NEAR INFRARED FOCAL INSTRUMENT FOR THE VERY LARGE TELESCOPE
INTERFEROMETER SPIE proc 4006, p 68-70, "VLT interferometer: a unique instrument
for high-resolution astronomy",
Garching, Germany, March 25-31, 2000
Abstract
:
AMBER is a focal instrument for the Very Large Telescope Interferometer
working in the near infrared from 1.1 to 2.4 micrometers . It has been
designed having in mind the General User of interferometric
observations and the full range of his possible astrophysical programs.
However the three programs used to define the key specifications have
been the study of Young Stellar Objects, the study of Active Galactic
Nuclei dust tori and broad line regions and the measure of masses and
spectra of hot Extra Solar Planets. AMBER combines up to three beams
produced by the VLTI 8 m Unit Telescopes equipped with Adaptive Optics
and/or by the 1.8 m Auxiliary Telescopes. The fringes are dispersed
with resolutions ranging from 35 to 10000. It is optimized for high
accuracy single mode measurements of the absolute visibility, of the
variation of the visibility and phase with wavelength (differential
interferometry) and of phase closure relations with three telescopes.
The instrument and its software are designed to allow a highly
automated user friendly operation and an easy maintenance.
14. Duvert G.; Mouillet D. ; Malbet F. ; Berio P. ; Forveille T.
, Aristidi E. ; Hofmann K.-H.; Mege P.
AMBER data
simulator SPIE proc 4006, p 217-223, "VLT interferometer: a unique
instrument for high-resolution astronomy", Garching, Germany, March 25-31, 2000
Abstract
:
We present the design and realization of the AMBER data simulator. This
tool provides the AMBER team with: (1) a way to test the performance
and sensitivity of AMBER wrt. external parameters (e.g., observed
source magnitude, AO correction); (2) a means to validate proposed
visibility retrieval algorithms; and (3) a mean to obtain realistic
data flows to test and implement the AMBER data reduction
software.
13. Beaumont H., Aime C., Aristidi E., Lanteri H.
EXPERIMENTAL
ANALYSIS OF IMAGE QUALITY FOR AN HORIZONTAL OVERWATER PROPAGATION Denver 96 Symposium on Optical Science,
Engineering, and Instrumentation
Denver, Colorado USA, 4-9 August 1996
Abstract
:
The effect of atmospheric turbulence on the imaging of scenes, for an
horizontal propagation of the light over a distance of 20 km, 15 meters
above the sea surface, was analyzed at visible wavelength using a 20 cm
telescope. Point-sources images were recorded during the night, and the
Fried parameter r0 was derived leading to values ranging from 1.5 to
3.6 cm. A very high level of scintillation was observed. Studies of
correlations between close-by sources lead to a very small domain of
isoplanatism. Daytime observations of an extended source are also
performed; an image motion of small spatial coherent length seems to be
drawn by an horizontal wind producing wave-like distortion of
horizontal lines and boiling-like of vertical ones.
12. Marcel Carbillet, Claude Aime, Eric Aristidi, Gilbert Ricort
HIGH
RESOLUTION MEASUREMENTS OF CLOSE BINARY STARS AND THE PROBABILITY
IMAGING TECHNIQUE ESO workshop : Science with the VLTI, Garching, 13-19 June 1996
Abstract
:
We report in this communication the first experimental results in the
visible range obtained by the Probability Imaging technique applied to
close binary stars. Speckle data of the well known binary beta Del as
well as the newly discovered one Moai 1 (Carbillet et al. 1996) are
processed. An analysis of the probability density functions,
combined with the classical visibility, is used to reconstruct the
binary systems.
Abstract
:
During its observing time, the satellite Hipparcos has discovered 13000
new double stars, measuring their position angles and separations close
to 100 milli-arcsec. A few of these systems have primary late type
star. The study of such systems is of interest for the knowledge of the
stellar evolution and the understanding of the mass loss process of
late type stars. Interacting mass exchange may exist in binary systems.
For the prototype of Mira stars, Omicron Ceti, photometric variations
of the compagnon result from this mass exchange. Our project is to
observe these systems with visible speckle interferometry, in order to
confirm the post-Hipparcos stars and to study the light curves of the
compagnons. A speckle experiment is being developed for that purpose at
the "Laser Lune telescope" (France). We present also in this
communication the observation of two post-Hipparcos late type stars
observed at Pic du Midi (France).
10. Carbillet M., Aristidi E., Ricort G. and Aime C.
PROBABILITY
IMAGING OF BINARY STARS FROM INFRARED SPECKLE OBSERVATIONS SPIE International Conference on
Holography and Correlation Optics.
SPIE vol. 2647, pp.422-432, Chernivtsy, Ukraine, 15-19 May, 1995
Abstract
:
We report in this communication experimental results obtained by the
technique of Probability Imaging (PI) applied to double stars in the
near-infrared. Intensity ratios and relative positions of components
are obtained for the data of six double stars in the near-infrared. The
two-fold probability density function (PDF) of one-dimensional images
is used to reconstruct the binary system. The data reduction is made
with a parametric approach, by minimizing a distance between observed
two-fold PDFs and modelled ones, obtained by using a close-by reference
star.
9. Ricort G., Lantéri H., Aime C., Aristidi E., Sultani F.
SUR L'ORDRE
D'ANALYSE D'UNE STRUCTURE DE SPECKLES EN ASTRONOMIE A HAUTE RESOLUTION
ANGULAIRE
Poster, 14e
colloque GRETSI sur le Traitement du Signal et des Images Juan-les-Pins, 13-16 sept.1993
Abstract
:
The paper deals with the problem of image reconstruction in astronomy
by means of a statistical analysis of the speckle pattern present at
the focus of a large telescope. Under the assumption that the N points
defining the object are well separated one another regard to the
telescope resolution, it is shown that a statistical analysis of order
N completely defines the statistical properties of the image speckle
pattern. This result is based upon the fact that the characteristic
function of order N+1 can be obtained from lower order ones.
APPLICATION
DU RECUIT SIMULE A L'INVERSION DE LA TRANSFORMATION DE POISSON-MANDEL 14e colloque GRETSI sur le Traitement du
Signal et des Images Juan-les-Pins,
13-16 sept 1993
Abstract
:
Nous présentons dans ce papier la mise en oeuvre du recuit simulé
ainsi que l'application de deux types de régularisations pour inverser
la transformation de POISSON-Mandel.
EFFECTS OF CLIPPED PHOTON DETECTION IN
THE TRIPLE CORRELATION TECHNIQUE ESO Conference in "High Resolution Imaging
by Interferometry II" Garching bei
Munchen, 14-18 octobre 1991, Beckers and F. Merkle eds , p 203-212
PROBABILITY IMAGING AT PHOTON-COUNTING
LEVELS ESO Conference in "High Resolution Imaging
by Interferometry II" Garching bei
Munchen, 14-18 octobre 1991, Beckers and F. Merkle eds , p 289-298
PROBABILITY
IMAGING OF EXTENDED ASTRONOMICAL SOURCES AT LOW LIGHT LEVELS OIC-ICO Topical Meeting, on Atmospheric,
Volume and Surface Scattering and Propagation, Florence, 27-31 Aout
1991
Abstract
:
We show the relevant role of the characteristic function (CF) in
Probability Imaging of extended astronomical sources. Low light level
and photon counting are considered. We propose iterative reconstruction
procedures using the analytical expression of the CF.
4. Aristidi E., Ricort G., Lantéri H., Aime C.
EFFECTS OF
CLIPPED PHOTON DETECTION IN SPECKLE INTERFEROMETRY OIC-ICO Topical Meeting, on Atmospheric,
Volume and Surface Scattering and Propagation, Florence, 27-31 Aout
1991
Abstract
:
3. Aristidi E.
VERS LA
TRES HAUTE RESOLUTION ANGULAIRE EN ASTRONOMIE : LA SYNTHESE
D'OUVERTURE Physique en Herbe, Poitiers, 1-5 Juillet 1991
2. Aristidi E.
IMAGERIE A HAUTE RESOLUTION EN
ASTRONOMIE OPTIQUE Physique en Herbe, Aussois, 25-29 Juin1990
1. Aime C., Aristidi E., Lantéri H., Ricort G.
SECOND
ORDER STATISTICS OF ASTRONOMICAL SPECKLE PATTERN USED FOR IMAGE
RECONSTRUCTION SPIE International Symposium Mathematical
Imaging, Digital Image Synthesis and Inverse Optics San Diego, California, 9-13 juillet 1990, SPIE Vol.
1351 pp. 628-639
Abstract
:
We report in this Communication the current
progress in development at the Nice University of the technique of
Probability Imaging based ona complete statistical analysis of the
speckle pattern observed at the focusof a large telescope. The
technique, which was first proposed for the imagingof double and
multiple stars, is here generalized to the image reconstructionof any
general extended astronomical object. Making use of a techniqueof
orthonormal expansion currently employed in statistical optics,
amathematical expression for the characteristic function of any order
ofthe speckle pattern is given as the inverse of the determinant of a
matrix whose elements are defined by the spatial correlation function
of the amplitudeof the point source speckle pattern and a diagonal
matrix representing theastronomical object. Recent results obtained for
the bright infrared doublestar zeta Aqr and simulations of the
implementation of the algorithm foroptical photon-counting detectors
with clipping problems are given. The use of the technique for
synthesized apertures is also considered.
Other publications
Scardia M., Prieur J.L., Pansecchi L., J. Ling, Argyle R.W., Aristidi E., et al.
Orbital elements of double stars: BU 453, A 819, STT 406, BU 367
IAU Commission G1 double stars circular 205(2021)
Scardia M., Prieur J.L., Pansecchi L., J. Ling, Argyle R.W., Aristidi E., et al.
Orbital elements of double stars: A 207
IAU Commission G1 double stars circular 202(2020)
Scardia M., Prieur J.L., Pansecchi L., J. Ling, Argyle R.W., Aristidi E., et al.
Orbital elements of double stars: BU 1185, A 122, A 570, HU 577
IAU Commission G1 double stars circular 201(2020)
Scardia M., Prieur J.L., Pansecchi L., J. Ling, Argyle R.W., Aristidi E., et al.
Orbital elements of double stars: STF 2281AB
IAU Commission G1 double stars circular 200(2020)
Scardia M., Prieur J.L., Pansecchi L., J. Ling, Argyle R.W., Aristidi E., et al.
Orbital elements of double stars: : HU 907, A 163 and STF 2576 FG
IAU Commission G1 double stars circular 199(2019)
J. Ling, Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Aristidi E., et al.
Orbital elements of double stars: STF 2672 and A 307
IAU Commission G1 double stars circular 198(2019)
M. Scardia, J.L. Prieur, L. Pansecchi, R. Argyle, J. Ling, E. Aristidi et al.
Orbital elements of double stars: STT 213AB, REU 1, MCA 55Aa,Ac and A 1226
IAU Commission G1 double stars circular 198(2019)
J. Ling, Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Aristidi E., et al.
Orbital elements of double stars: BU 602 and HU 143 Aa,Ab
IAU Commission G1 double stars circular 197(2019)
E. Aristidi
Grands télescopes : le choix du bon site
Ciel et Espace Mars 2018(2018)
M. Scardia, J.–L. Prieur, L. Pansecchi, R. Argyle, J. Ling, E. Aristidi et al.
Orbital elements of double stars: ADS 7704 and A 1101 AB
IAU Commission G1 double stars circular 196(2018)
Ling, M. Scardia, J.–L. Prieur, L. Pansecchi, R. Argyle, E. Aristidi et al.
Orbital elements of double stars: ADS 1005
IAU Commission G1 double stars circular 195(2018)
M. Scardia, J.–L. Prieur, L. Pansecchi, R. Argyle, J. Ling, E. Aristidi et al.
Orbital elements of double stars: ADS 1548
IAU Commission G1 double stars circular 194(2018)
Ling, M. Scardia, J.L. Prieur, L. Pansecchi, R. Argyle, A. Zanutta, E. Aristidi et al.
Orbital elements of double stars: 15186+2356 and ADS 12746
IAU Commission G1 double stars circular 193(2017)
M. Scardia, J.L. Prieur, L. Pansecchi, R. Argyle, J. Ling, E. Aristidi, et al.
Orbital elements of double stars: ADS 9318, 10206 and 16448
IAU Commission G1 double stars circular 193(2017)
J. Ling, Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Zanutta A., Aristidi E., Abe L., Bendjoya P., Combier-Dimur C., Rivet J.P., Suarez O., Vernet D.
New orbits of binary stars ADS 7435, ADS 7785
IAU Commission G1 double stars circular 192(2017)
Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Ling J., Zanutta A., Aristidi E., Abe L., Bendjoya P., Combier-Dimur C., Rivet J.P., Suarez O., Vernet D.
New orbits of binary stars BU 453AB and A 2059
IAU Commission G1 double stars circular 191(2017)
Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Aristidi E., Abe L., Bendjoya P., Combier-Dimur C., Rivet J.P., Suarez O., Vernet D.
Orbite de : ADS 13169 IAU Commission G1 double stars circular 190(2016)
Scardia M., Prieur J.L., Rivet J.P., Vernet D., Pansecchi L., Argyle R.W., Aristidi E., Abe L., Bendjoya P., Combier-Dimur C., Suarez O.
Orbites de : ADS 5958, ADS 6276, ADS 7294, ADS 8211 IAU Commission G1 double stars circular 189(2016)
Scardia M., Prieur J.L., Pansecchi L., Argyle R.W., Aristidi E., Abe L., Bendjoya P., Dimur C., Rivet J.P., Suarez O., Vernet D.
The speckle camera pisco is now mounted on the 104 cm "Epsilon" telescope of the Observatoire de la Côte
d'Azur, on the Plateau de Calern, France
IAU Commission G1 double stars circular 187(2015)
Scardia M., Prieur J.L., Koechlin L., Aristidi, Lampens P.,
Strigachev A., Oblak E., Kurpinska-Winiarska M., Ghigo M., Mazzoleni
F., Sala,
The speckle camera PISCO is now
operational on the 1-meter telescope of INAF - Oss. di Brera, Merate,
Italy IAU Commission 26 circulaire 153 (2004)
Scardia M., Prieur J.L., Aristidi, Koechlin L., Sala M.,
Orbite de : ADS 5447, ADS 8035 IAU Commission 26 circulaire 153 (2004)
Scardia M., Prieur J.L., Koechlin L., Aristidi E.,
Orbites de : WDS 06474+1812, WDS
11037+6145 IAU Commission 26 circulaire 151 (2003)
Scardia M., Prieur J.L., Koechlin L., Aristidi E.,
Orbite de : WDS 19296-1239 IAU Commission 26 circulaire 150 (2003)
Scardia M., Prieur J.L., Koechlin L., Aristidi E.,
Orbite de : ADS 5514, ADS 10235, WDS
21001+0731 IAU Commission 26 circulaire 149 (Fev.
2003)
Scardia M., Prieur J.-L., Koechlin L., Aristidi E.
Orbites de : ADS 10279, ADS 16650 IAU Commission 26 circulaire 148
(Octobre 2002)
Scardia M., Prieur J.-L., Koechlin L., Aristidi E.,
Orbites de : ADS 7307, ADS 17030 IAU Commission 26 circulaire 147 (Juin
2002)
Scardia M., Prieur J.-L., Koechlin L., Aristidi E.,
Orbites de : WDS 03344+2428, WDS
16366+6948, WDS 21125+2821, WDS 21423+0555 IAU Commission 26 circulaire 146 (Fev
2002)
Scardia M., Prieur J.-L., Koechlin L., Aristidi E.,