These favorable conditions have led astronomers to characterise more precisely the astronomical quality of Dome C: the process of site testing.
? E. Aristidi (2006)The instruments used to test the site of Dome C are installed on the ground or on wood platforms at 8 m above the ground-level. The two towers of the Concordia station are in the background.
The Earth's atmosphere is one of the astronomers' greatest enemies: The lowest 25 to 30 km of the atmosphere is made up of many layers lying on top of each other, each with different pressure, temperature and humidity, causing turbulence. As the starlight crosses these layers, it is disturbed: this is optical seeing. By site testing, a few fundamental parameters are determined. These parameters are compared with those of the best current world astronomical sites such as Cerro Paranal in Chile or Mauna Kea in Hawaii, to evaluate the astronomical quality of the site. Furthermore, these parameters determine the requirements of an optical system to correct, in real time, the deformations produced by the atmosphere: Adaptive Optics.
? E. Aristidi (2006)
Video of a star at the focus of a ground telescope. The light coming from this star is disturbed when it travels through the Earth's atmosphere. The crossed layers present differences of pressures, temperature and moisture which the astronomers are trying to measure.
The site testing thus consists in determining a certain number of fundamental parameters to evaluate quantitatively the astronomical quality of the site. These parameters are compared with those of the best current world astronomical sites such as Cerro Paranal in Chile or Mauna Kea in Hawaii. Furthermore these parameters are very important to determine thereafter the instrumental constraints of a system able to correct in real time deformations induced by the atmosphere : adaptive optics.
)
