Status and Plans of the Russian Deep Space Network with Emphasis on the VLBI/Delta-DOR Techniques

The differential VLBI technique (delta-VLBI) is applied for measuring spacecraft position with accuracy up to 1 mas. This procedure allows to link the sky position of object with the position of close ICRF quasar on the celestial sphere. Few delta-VLBI measurements can urgently improve the knowledge of object trajectory in the times of critical maneuvers. The Russian Deep Space Network that was based on three large antennas: 70 m in Evpatoria (Ukraine) and Ussuriysk (Far East), and 64 m in Bear Lakes (near Moscow) arranged the trial delta-VLBI experiments with help of four scientific institutions. The specialized "Orion" system for regular delta-VLBI measurements was not finally completed. The series of delta-VLBI runs was carried out from 1984 to 1993 for the Venus-15, Vega-1, 2 and Phobos-1, 2 interplanetary stations, Astron and Granat highly-apogee spacecrafts. Since 1999 the differential VLBI radar (VLBR) method is under development using 6-cm transmitter in the Evpatoria to radio sound the space objects. The VLBR observations of space debris objects at geostationary and highly elliptical orbits, Venus and Mars planets were arranged to determine their trajectories in Radio Reference Frame and measure the variations of proper rotation. The further development is connected with Phobos sample return mission. It is planned to adjust the delta-VLBI technique in near real time with translation of signals from antennas to correlator through Internet.