Optical Turbulence On The Antarctic Plateau

Atmospheric turbulence results taken on the Antarctic plateau are presented in this thesis. Covering two high sites: South Pole and Dome C, this work describes their seeing and meteorological conditions. Using an acoustic sounder to study the turbulence profile of the first kilometre of the atmosphere and a Differential Image Motion Monitor (DIMM) to investigate the integrated seeing we are able to deduce important atmospheric parameters such as the Fried parameter (r0) and the isoplanatic angle (θ0). It was found that at the two sites, the free atmosphere (above the first kilometer) was extremely stable and contributed between 0.2′′ and 0.3′′ of the total seeing with no evidence of jet or vortex peaks of strong turbulence. The boundary layer turbulence is what differentiates the two sites. Located on the Western flank of the plateau, the South Pole is prone to katabatic winds. Dome C on the other hand is on a local maximum of the plateau and the wind conditions are amongst the calmest in the world. Also linked to the topography is the vertical extent of the temperature inversion that is required to create optical turbulence. At the South Pole the inversion reaches 300 m and only 30 m at Dome C. This difference results in relatively poor seeing conditions at the South Pole ('1.8′′) and excellent at Dome C (0.27′′). The strong correlation between the seeing and the ground layer meteorological conditions indicates that even better seeing could be found at Dome A, the highest point of the plateau. Having most of the turbulence near the ground is also incredibly advantageous for adaptive optics. The isoplanatic angle is respectively 3.3′′ and 5.7′′ for the South Pole and Dome C. This is significantly larger than at temperate sites where the average isoplanatic angle rarely exceeds 2′′. This means that wider fields can be corrected without the complication of conjugation to specific layers. For such purpose the potential is even more