Dome C, also known as Dome Circe or Dome Charlie, located at Antarctica at an altitude of 3,233 metres (10,607 ft) above sea level, is one of several summits or "domes" of the Antarctic Ice Sheet. Dome C is located on the Antarctic Plateau, 1,100 kilometres (680 mi) inland from the French research station at Dumont D'Urville, 1,100 kilometres (680 mi) inland from the Australian Casey Station and 1,200 kilometres (750 mi) inland from the Italian Zucchelli station at Terra Nova Bay. Russia's Vostok Station is 560 kilometres (350 mi) away. Dome C is the site of the Concordia Research Station, jointly operated by France and Italy.
Dome C is one of the coldest places on Earth. Temperatures hardly rise above −25 °C (−13 °F) in summer and can fall below −80 °C (−112 °F) in winter. The annual average air temperature is −54.5 °C (−66.1 °F). Humidity is low and it is also very dry, with very little precipitation throughout the year.Dome C does not experience the katabatic winds typical of the coastal regions of Antarctica because of its elevated location and its relative distance from the edges of the Antarctic Plateau. Typical wind speed in winter is 2.8 m/s (6 mph).
Dome C is situated on top of the Antarctic Plateau, the world's largest desert. No animals or plants live at a distance of more than a few tenths of a kilometre from the Southern Ocean. However, skuas have been spotted overflying the station, 1,200 kilometres (750 mi) away from their nearest food sources. It is believed that these birds have learned to cross the continent instead of circumnavigating it.
Dome C is notable for its potential to be an extremely good astronomical observation site; the transparency of the Antarctic atmosphere allows stars to be observed, even when the Sun is at its highest possible elevation angle of 38°. The good viewing is due to very low infrared sky emission, extremely low humidity, a high percentage of cloud-free time, low atmospheric aerosol and dust content, and an absence of light pollution other than auroras and moonlight. This location is a serious candidate for the ESO's E-ELT project (a telescope of 30 metres (98 ft) to 60 metres (200 ft) mirror diameter). However, sky coverage is less than at lower latitude locations as northern celestial hemisphere objects never rise or are too low above the horizon.
Writing in the Proceedings of the Astronomical Society of the Pacific in 2005, Karim Agabi et al. discuss the suitability of the site for astronomy in terms of the seeing.They determined the median seeing (measured with a Differential Image Motion Monitor placed on top of an 8.5 metres (28 ft) high tower) to be 1.3±0.8 arcseconds. This is significantly worse than most major observatory sites, but similar to other observatories in Antarctica. However, they found (using balloons) that 87% of turbulence was below 36 meters. A telescope built on a tower could rise above this "boundary layer" and achieve excellent seeing. The boundary layer is 200 metres (660 ft) at the South Pole and may be as low as 20 metres (66 ft) at Dome A.
In an earlier (2004) paper, Lawrence et al. considered the site and concluded that "Dome C is the best ground-based site to develop a new astronomical observatory".This team measured superior seeing of 0.27 arcseconds, twice as small as at Mauna Kea Observatory. This figure was taken with an instrument insensitive to near-ground turbulence and so it is comparable to the 0.35 arcseconds Agabi et al. measured for "free atmospheric seeing".The 2004 experiments to measure the astronomical conditions at the site were unattended, controlled by a computer system that had to supervise the generation of its own electricity using a jet-fuel powered stirling engine. The computer, running Linux, communicated with the outside world using an Iridium phone.