DRIFT SCANNING FROM GROUND AND IN-SPACE

The drift scanning technique offers, in principle, a simple and effici ent method for imaging wide regions of the sky with intrinsic high ast rometric accuracy. its performance is analyzed in two distinct environ ments, namely from a small class ground based telescope and a spacebor ne interferometer. In particular, the study is referred to the propose d ESA cornerstone mission GAIA (Global Astrometric Interferometer for Astrophysics). The constant clock rate of a CCD, due to the declinatio n dependent sidereal speed variation, results in a systematic image sm earing, which Limits the positional accuracy. Moreover, the readout ti ming accuracy provides an additional random noise corresponding to a d rift speed jitter. Stability requirements on the order of 10(-6) or be tter have to be fulfilled for the space option. Both effects can be ad dressed by proper system design; provisional implementation strategies are discussed for both applications.