A frozen desert far from all sources of human pollution, located on the high plateau of the Antarctic continent, Dome C is a dream for astronomers. Its geography and meteorology combine to yield exceptional conditions for observing the sky.
Extremely favorable geographical conditions!
Firstly, it is isolated: The Antarctic continent has no light or chemical pollution to harm astronomical observations. Secondly, Antarctica is a true desert.
Dome C is located at an altitude of 3233 meters, on the Antarctic high plateau. Because of this special location, Dome C is free from the powerful katabatic winds which sink downhill toward the coast, particularly to the Dumont D' Urville station, at 1100 km, where 324 km/h winds have been recorded.
Low-pressure systems circulate around the continent and rarely penetrate inland. Thus, surprisingly, it snows very little in Antarctica: Between 2 and 10 cm per year at Dome C! The very dry air gives Dome C excellent conditions for infrared astronomy (see ?Looking at the sky in new spectral windows?). The atmosphere's moisture content blocks infrared light: It retains the heat radiated upwards from the ground (the ?greenhouse effect?), and is also a particularly awkward filter for the infrared radiation coming from space, which astronomers want to observe. Thirdly, because of its polar location, the absence of day/night cycles for much of the year allows continuous observations over long periods of the stars in winter, or the sun during the southern summer. It was this property that led to the beginning of Antarctic astronomy in 1979 at the South Pole, with 6 days of continuous solar observations.
? E. Bondoux (2008)
The Concordia station is located at Dome C, 75? South?; because of its great distance from the geographical South Pole, there are 4 real annual seasons at Dome C, as well as in the temperate latitudes. The only differences (but very promising for astronomy) are?: the southern summer has 3 months of continuous daytime (december ? january ? february) and the southern summer has 3 months of continuous nighttime (june ? july ? august).?
In addition to these conditions, which are found throughout the Antarctic continent, there some which are peculiar to Dome C. 3233 metres above sea level, astronomers see significantly less atmospheric turbulence, which is responsible for the degradation of stellar images. Because of its location on the high plateau, Dome C is largely free of katabatics - powerful winds which sink downhill from the summits of the antarctic plateau, reaching 300 km/h at the coast. Finally, southern auroras, which can contaminate astronomical observations, are very rare at Dome C, which lies near the centre of the auroral oval, so that auroras are usually below the horizon.
)
)
