In February 1997, the "HALCA" (MUSES-B), which was the world's first radio-astronomy satellite that enabled the "Space Very Long Baseline Interferometer" (Space VLBI) method, was launched by M-V launch Vehicle No. 1 (M-V-1) from the Uchinoura Space Center (USC.) The satellite observed deep-space including the high-resolution imaging of active galactic nuclei. The HALCA mission was one segment of the major international collaboration called the VLBI Space Observatory Program (VSOP), and it became a core part of the VSOP.
Based on the results of the VSOP, the upgraded project "VSOP-2" is currently planned. The "VSOP-2" is a successive plan of the VSOP to realize high-resolution celestial observations by launching a satellite with a radio-telescope onboard. The "ASTRO-G" is the satellite for the "VSOP-2."
The VSOP mission will focus on observations in the millimeter wave-band that enables the imaging of objects directly with the best resolution. This will allow studies of fields where extreme space physical conditions are encountered, including the elucidation of "the scale of the accretion disk and jet generation and acceleration region surrounding the active galactic nuclei black holes." Compared to the telescope onboard the HALCA, the ASTRO-G telescope is expected to be 10 times higher in frequency. It will also have improved resolution, higher sensitivity and astrometry using the phase referencing technique, and a magnetic field measurement function by polarized wave observation.