Gravimetric missions by VLBI and Doppler in SELENE

SELENE is a mission in preparation for launch in 2007 by JAXA (Japan Aerospace Exploration Agency). It execute 15 experiments, two of which (RSAT and VRAD) are gravimetric experiments using radio waves. RSAT (Relay Satellite Transponder) mission will undertake 4-way Doppler measurements of the main orbiter through the Rstar sub-satellite. This is in addition to 2-way Doppler and ranging measurements of the satellites and will realize the first direct observation of the gravity fields on the far side of the Moon. VRAD (Differential VLBI Radio Source) mission involves observing the trajectories of Rstar and Vstar sub-satellites using differential VLBI with both a Japanese network (VERA), and an international network. We have already finished development of the onboard instruments and are carrying out proto-flight tests under various conditions. We have also performed test VLBI observations of orbiters with the international network.