History, Present Status & Future of Site Testing at Dome C
Résumé
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).