Microwave technology innovations in orbiting VLBI

The radio astronomical technique of very long baseline interferometry (VLBI) will soon be extended beyond the Earth's surface by placing antennas and receiving systems in high Earth orbit. Two such orbiting VLBI telescopes are expected to be in operation by 1995. The technical challenges of these projects have produced several interesting innovations in the microwave area, including designs of large, deployable antennas; designs of multifrequency feed systems; cryogenic low-noise amplifiers; and methods of precise time synchronization with ground telescopes.<>