Time has come to implement a new way to study the stellar physics from the ground with long-term uninterrupted time series, multi-color photometry, flexibility during observing runs and all for less money. PAIX, Photometer AntarctIca eXtinction, gives new insight to cope with unresolved stellar enigma and stellar oscillation challenges and bears witness, for the first time, to a new technology of the polar instrumental robotization under extreme human and weather conditions in the heart of Antarctica. In fact, the stellar pulsation plays a crucial role in understanding the Universe, however progress is limited by the data accuracy needed to detect numerous modes of oscillations with small amplitudes and by the discontinuous nature of typical ground-based data strings which often introduce ambiguities in the determination of oscillation frequencies. The recent space missions enable to overcome both difficulties, However, the outcome of the space missions shows large gaps in terms of flexibility during the observing runs, the choice of targets, the repair of failures and the inexorable high costs. We present here the new technology from Antarctica, in particular from South Polar Site Dome C that benefits from great image quality and 150 days high time coverage, where the seeing reaches a median value of 1 arcsec during the polar night. We briefly describe the instrumental performances of PAIX, its low-cost commercial components, robotic telescope, multi-band photometer and automatic control, working under harsh weather conditions, even when the temperature reach values as low as -80°C. The polar mission PAIX challenges the space missions and even has more advantages than CoRoT and KEPLER in observing in UBVRI bands and then collecting multicolor light curves simultaneously of several targets. We discuss here the first outcomes of stellar physics from the heart of Antarctica during 10 polar nights and PAIX new results and perspectives on the pulsating stars from Antarctica, especially the connection between the stellar pulsation enigma and the Universe mysteries. Finally, we highlight the impact of PAIX -the robotic Antarctica photometer- on the Astronomy development.
In this invited paper, we implement a new way to study the stellar oscillations, pulsations and their evolutionary properties with long uninterrupted and continuous precision observations over 150 days from the ground, and without the regular interruptions imposed by the earth rotation. PAIX–First Robotic Antarctica Polar Mission– gives a new insight to cope with unresolved stellar enigma and stellar oscillation challenges and offers a great opportunity to benefit from an access to the best astronomical site on Earth –DomeC–. The project is made of low cost commercial components, and achieves astrophysical measurement time-series of stellar physics fields, challenging photometry from space that shows large gaps in terms of flexibility during the observing runs, the choice of targets, the repair of failures and the inexorable high costs. PAIX has yet more advantages than space missions in observing in UBV RI bands and then collecting unprecedented simultaneous multicolor light curves of several targets. We give a brief history of the Astronomy in Antarctica and describe the first polar robotized mission PAIX and the outcome of stellar physics from the heart of Antarctica during several polar nights. We briefly discuss our first results and perspectives on the pulsating stars and its evolution from Antarctica, especially the connection between temporal hydrodynamic phenomena and cyclic modulations. Finally, we highlight the impact of PAIX on the stellar physics study and the remaining challenges to successfully accomplish the Universe explorations under extreme conditions.
The quality of astronomical observations is strongly related to the quality properties of the atmosphere. This parameter is important for the determination of the observation modes, and for observation program, the socalled flexible scheduling. We propose to present the implementation of the WRF model in order to routinely and automatically forecast the optical conditions. The purpose of our study is to predict 24 hours ahead the optical conditions above an observatory to optimize the observation time, not only the meteorological conditions at ground level, but also the vertical distribution of the optical turbulence and the wind speed, i.e the so-called astronomical seeing. The seeing is computed using the Trinquet-Vernin model coupled with the vertical profiles of the wind shear and the potential temperature predicted by the WRF model. We made a comparison between the WRF output and the in situ measurements made with the DIMM and an automatic weather station above the Observatorio del Roque de los Muchachos, Canary Island. Here we show that the increase of resolution in both the terrain model and 3D grid yields better forecast when compared with in situ optical and meteorological observations.
To prepare long baseline interferometric arrays with large telescopes, at Dome C on the Antarctic plateau, we have to know the effect of the strong turbulent surface layer on the wave front propagation as sensed by two telescopes. The main limit of long baseline interferometer is the phase fluctuations, induced by the optical turbulence above each telescope and towarsds the focal beam combiner. PropHAn (Horizontal Propagation in Antarctica) is an instrument to study the optical turbulence effect on the horizontal propagation. PropHAn is designed to retrieve the phase fluctuations between two different horizontal paths of a coherent laser beam. It
is a Michelson periscopic interferometer with a variable baseline from 10 cm up to 1 m. The fringe pattern is recorded on a fast CCD camera to freeze the turbulent motions. The main goal of PropHAn is to test a simple interferometric table in Antarctic conditions, and to provide statistics on the turbulent coherence time and the
differential pistonmode for a 1 m baseline. These results, in complement with the results provided by DIMM, C2N balloons profiles and Single Star Scidar measurements, would be required to design long baseline interferometers and fringe tracker at Dome C.
Here we present the first photometric extinction measurements in the visible range performed at Dome C in
Antarctica, using PAIX photometer (Photometer AntarctIca eXtinction). It is made with "off the shelf" components,
Audine camera at the focus of Blazhko telescope, a Meade M16 diaphragmed down to 15 cm. For an
exposure time of 60 s without filter, a 10th V-magnitude star is measured with a precision of 1/100 mag. A first
statistics over 16 nights in August 2007 leads to a 0.5 magnitude per air mass extinction, may be due to high
altitude cirrus. This rather simple experiment shows that continuous observations can be performed at Dome C,
allowing high frequency resolution on pulsation and asteroseismology studies. Light curves of one of RR Lyrae
stars: SAra were established. They show the typical trend of a RRLyrae star.
A recent sophisticated photometer, PAIX II, has been installed recently at Dome C during polar summer
2008, with a ST10 XME camera, automatic guiding, auto focusing and Johnson/Bessel UBVRI filter wheels.
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
profile of the optical turbulence intensity C2n. The C2n
median profile, mean temperature and mean horizontal
wind speed are given. The C2n
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,
coherence time τ0, isoplanatic angle θ0 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.
At Dome C, Antarctica, the whole turbulence is reduced to a boundary layer of about 50 meters. WHITE is a project of an infrared survey based on a 2-m telescope using a ground-layer adaptive-optics instrument to obtain high angular resolution on a wide field of view. Simulation results obtained both analytically and from a numerical end-to-end approach are presented and then compared.
The French-Italian interferometric gravitational wave detector VIRGO is currently being commissioned. Its principal instrument is a Michelson interferometer with 3 km long optical cavities in the arms and a power-recycling mirror. This paper gives an overview of the present status of the system. We report on the presently attained sensitivity and the system’s performance during the recent commissioning runs.
The goal of the VIRGO program is to build a giant Michelson type interferometer (3 kilometer long arms) to detect gravitational waves. Large optical components (350 mm in diameter), having extremely low loss at 1064 nm, are needed. Today, the Ion beam Sputtering is the only deposition technique able to produce optical components with such performances.
Consequently, a large ion beam sputtering deposition system was built to coat large optics up to 700 mm in diameter. The performances of this coater are described in term of layer uniformity on large scale and optical losses (absorption and scattering characterization).
The VIRGO interferometer needs six main mirrors. The first set was ready in June 2002 and its installation is in progress on the VIRGO site (Italy). The optical performances of this first set are discussed. The requirements at 1064 nm are all satisfied. Indeed, the absorption level is close to 1 ppm (part per million), the scattering is lower than 5 ppm and the R.M.S. wavefront of these optics is lower than 8 nm on 150 mm in diameter. Finally, some solutions are proposed to further improve these performance, especially the absorption level (lower than 0.1 ppm) and the mechanical quality factor Q of the mirrors (thermal noise reduction).