VRAD (SELENE VLBI Radio Satellite, VStar, Ouna)

VRAD [JAXA]

VRAD (Very-Long-Baseline-Interferometer Radio source), later renamed Ouna, is a subsatellite to the Japanese SELENE (Kaguya) lunar orbiter and will be used to conduct precise investigations on the position and precession of the Moon. Radio waves from the VRAD and RSat are received at VERA radio telescopes in NAOJ and others. Orbits of the sub-satellites are precisely determined by tracking the radio sources onboard sub-satellites with differential VLBI, which contributes the accuracy of the gravity field, especially on the lunar limb areas.