VLBI in the 1990s

The feasibility of earth-to-space VLBI measurements has been demonstrated by a series of experiments using the NASA tracking and data relay satellite (TDRSS) in combination with ground radio telescopes in Australia and Japan. Three dedicated space VLBI missions are discussed for a possible launch in the 1990s. The ability of global and space VLBI systems to image astronomical objects with sub-mas angular resolution and with high fidelity and dynamic range will open up a wide range of important scientific opportunities. Global VLBI observations made at 1.3 cm wavelength will have an angular resolution of only 0.3 mas, corresponding to 1 km on solar system scales, 1 AU in the Galaxy, 0.01 pc for nearby galaxies, and several pc throughout the universe.