An instrument named the grating scale monitor for measuring the outer scale L0 from the angle-of-arrival (AA) fluctuations of a perturbed wave front was developed a few years ago at Nice University. The AA is detected with a 5-ms time resolution by modulation of the stellar image in a small telescope with a grating. One uses the normalized covariance of AA fluctuations to estimate L0. A new version of this instrument, the generalized seeing monitor (GSM) is described. It consists of four identical modules for measuring the AA at four locations on the wave front. A spatiotemporal analysis of these data leads to the determination of seeing epsilon0, outer scale L0, and the wave-front speed. In addition, isoplanatic angle theta0 is determined from scintillation, making the characterization of turbulence with the GSM almost complete. We describe the instrument and make a detailed analysis of its performance and accuracy. Several site-testing campaigns have been conducted with the GSM: at La Silla (Chile), Oukaïmeden (Morocco), Maidanak (Uzbekistan), and Cerro Pachon and Cerro Paranal (Chile). The main results of these campaigns are presented and discussed.

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 2 n (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 = 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.

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 2 n 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.

We present summer site testing results based on DIMM data obtained at Dome C, Antarctica. These data were collected on the bright star Canopus during two 3-months summer campaigns in 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 and a median isoplanatic angle of 6.8 . The seeing appears to have a deep minimum around 0.4 almost every day in late afternoon.

No abstract