ANTARCTIC SITE TESTING - MICROTHERMAL MEASUREMENTS OF SURFACE-LAYER SEEING AT THE SOUTH-POLE

Results from experiments measuring the optical seeing in the surface l ayer at the South Pole Station are presented. Seeing measurements were taken over 49 data runs between April and August 1994, using microthe rmal sensors placed at 3 levels on a 27 m-high mast. The seeing contri bution from this region was quite large in comparison with similar exp eriments performed at other sites, with a mean value measured over thi s period of 0.64 ''. However, there is often a significant decrease in the optical turbulence over the height of the mast, with mean values of 0.37 '' and 0.46 '' measured in the upper (17-27 m) and lower (7-17 m) sections respectively. These measurements coincide with a large an d highly variable temperature inversion, the behaviour of which is oft en well correlated with the observed turbulence profile. The results c an be roughly separated into four or five categories, characterised by the temperature inversion alone. Further analysis of the data should provide some predictive power about the likely optical turbulence prof ile of the surface layer in given observing conditions.