Atmospheric and astronomical conditions at Dome A, Antarctica

• Main Author: Sims, Geoffrey
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: UNSW, Sydney 2013
• Subjects: Aurora; Antarctica; Astronomy; Sky brightness; Twilight; Water vapour; Dome A; Ridge A; Airglow; Antarctic; Austral; The Antarctic; Antarc*
• Online Access: http://hdl.handle.net/1959.4/53042; https://unsworks.unsw.edu.au/bitstreams/3ff1a360-3e42-4aa9-b335-16bf786178b8/download; https://doi.org/10.26190/unsworks/16484

Antarctica has long been recognised as an exceptionally good location for astronomy. On the Antarctic plateau, high altitudes combine with cold temperatures, low wind speeds, and a low atmospheric boundary layer to produce the best sites for optical, infrared and sub-millimetre astronomy on the planet. Dome A, situated at the highest point on the plateau, is one of the newer sites to have been established. As Dome A is still in the `site testing' phase, a number of site characteristics are yet to be quantified, of which this thesis examines four: Far away from artificial light pollution, even in the absence of moonlight the night sky is never completely dark. Airglow, and more importantly at polar latitudes, the aurora, can significantly brighten the night sky for extended periods of time. A statistical analysis of the airglow and auroral contribution to the optical sky brightness at Dome A is presented, derived from spectroscopic observations spanning the Austral winter of 2009. To examine the sky brightness more generally, optical imagery is used to demonstrate how cloud cover, extinction, and aurora distribution may be determined across the entire sky. Another consequence of high latitude observing sites is the extended periods of deep twilight that result from the Sun's near-horizontal motion across the sky. As such, it is very important to determine at what solar zenith distance twilight ends, as this will ultimately determine the amount of available observing time. The zenith distance at which the sky becomes completely dark is obtained as a function of wavelength, as well as for a number of standard astronomical filters. Finally, the amount of precipitable water vapour in the atmosphere above the Antarctic plateau is estimated using both ground-based and satellite data. The variations and stability are examined, in the context of searching for the best sub-millimetre observing site on Earth.