ИСТИНА

The gravitational red shift effect belongs to the experimental basis of General Relativity and was reliably registered. At present it has to be taken into account in satellite navigation, chronometric geodesy and other applications. At the same time the measurement of this effect with an increased accuracy is important in searching for a new physics behind the General Relativity. Experimental studies of gravitation using spacecrafts are complicated by the necessity of separating tiny gravitational effects from much larger contributions due to nonrelativistic and relativistic Doppler, ionospheric and tropospheric phenomena, instrumental noise, etc. Compensation of such effects becomes possible with data acquisition systems using concurrent frequency measurements of 1- and 2-way radio links as well as satellite laser ranging. We discuss the compensation schemes used by the GP-A and ACES missions as well as our own approach developed for the RadioAstron spacecraft. We also present a status update of the gravitational redshift experiment with RadioAstron using the developed technique.