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 factor. We give the corresponding filter in the Fourier plane. As an illustration, we describe the propagation of wave with a spatial sinusoidal amplitude, introduce lenses as quadratic phase transmissions, discuss their Fourier transform properties and give some properties of Soret screens. Classical diffractions of rectangular diaphragms are also given here. In a second part of the paper, the presentation turns into the use of external occulters in coronagraphy for the detection of exoplanets and the study of the solar corona. Making use of Lommel series expansions, we obtain the analytical expression for the diffraction of a circular opaque screen, giving thereby the complete formalism for the Arago-Poisson spot. We include there shaped occulters. The paper ends up with a brief application to incoherent imaging in astronomy.

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).

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 Cn2. We report here the first analysis of these data.

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.

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.

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.

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.

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".

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.

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.

Hereafter we give a brief history of our contribution to astronomical site testing in Antarctica, at least for thehigh 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 Chicagowith the participation of Peter Gillingham, Al Harper and Jean Vernin where each one took the respectiveresponsibility 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 abovethe ice level.From this study, it becomes clear that the noticeable katabatic wind present at South Pole was generatingthis huge surface layer and that is why we oriented our astronomical site characterization towardDôme 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 seeingwas 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 motionmonitor (DIMM) was also setup with success. At mid winter, Agabi et al. (2006, PASP, 118, 344) showed that mostof the optical turbulence came from the first 30 m surface layer and very little from the rest of theatmosphere (1.3 arcsec above 8.5 m and 0.37 arcsec above 30 m).

Here we present the first light of the Single Star Scidar (SSS) at Dome C, during January 2005 andthe first results obtained during the winter 2006. We recall the SSS principle, how it is designedto resist to very low temperatures and to be adjusted in a very simple way. No exemple of longperiod of observation can be given since the huge amount of data cannot be sent back to our laboratoryto 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 opticalturbulence. Almost 300 hours of observations have been taken successfully during winter 2006.

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 14'' 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.

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.

IRAN is a method of beam-combination in thehypertelescope imaging technique recently introduced byLabeyrie 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 apseudo 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.

We present results of daytime site testing at Dome C in summer2003–2004. Daytime seeing has been monitored during 2$\frac{1}{2}$months using a DIMM on the bright star Canopus, giving median value of0.54 arcsec. An every-day best seeing period has been observed around5 pm with seeing around 0.3 arcsec. First isoplanatic anglemeasurements, based on stellar scintillation, were also performedduring the month of January 2004, and have given median value of 6.8 arcsec.


This paper describes a coronagraphic nulling interferometer calledKEOPS (Kiloparsec Explorer for Optical Planet Search) to be placedon the Dome C plateau of Antarctica. KEOPS is an interferometricarray of 39 1 m–2 m telescopes spread over kilometric baselines andoperated in the thermal IR region. It could search and characterizeall potential exoEarths within the 1 kpc diameter region observablefrom Dome C. We argue that even in the very difficult operationconditions of Antarctica, such a facility can compete at a muchlower cost with the non-zero risk space missions, both for for ExPNssearch and their spectroscopic characterization plus sub-massnap-shot imaging of galactic and extra-galactic compact sources.

We present wind and temperature profiles at Dome C measured during thepolar summer by balloon born sonds. Data from 197 flights have beenprocessed for 4 campaigns between 2000 and 2004. We show theexceptionnal wind conditions at Dome C: averaged ground wind speed is 3.6 m s-1. We noticed in mid-november the presence of high altitude strong winds (40 m s-1) probably due to the polar vortex which disappear in summer. These winds seem to have no effect on seeing measurements made with a DIMM at the same period. Temperature profiles exhibit a minimum at height 5500 m (over the snow surface) that defines the tropopause. Surface layer temperature profile has negative gradient in the first 50 m above ground in the afternoon and a strong inversion layer (5°C over 50 m) around midnight. Wind profiles are compared with other astronomical sites, and with a meteorological model from Meteo France.

We present a beam combining technique capable of directinstantaneous imaging. The particularity is that the image (or PSID, point source intensity distribution) is formed in apupil plane. We present the concept on a theoretical basis,comment on the PSID for on- and off-axis sources and finallycompare it to Fizeau imaging. Future experiments and reflectionsabout this concept are finally considered.

On the Antarctica plateau, a joint project of french and italianpolar programmes in just near completion: the Concordia stationwill be open for winterover operation in 2005. The high altitudeand high latitude of this site, the exceptionally cold, clear andstable atmosphere, the almost indefinitely flat snow surface andthe not so difficult access make this site the most promising onEarth for future ground based astronomical projects in variousfields, including High Angular Resolution and High ContrastImaging.