The VSOP mission: A general introduction and current overview Original Research Article

The Institute of Space and Astronautical Science (ISAS) launched the first space VLBI (Very Long Baseline Interferometry) satellite, HALCA, in February 1997. After completing a series of engineering experiments to verify space-VLBI observations, the first VLBI fringes and images were obtained in May and in June, respectively. HALCA has now been operated for science observations at 1.6 and 5 GHz for the VSOP (VLBI Space Observatory Programme) project in cooperation with many organizations and radio telescopes around the world. In this paper the current science activities of the mission are reviewed and results presented.