Radio astronomy gets off the ground.

That dream became reality last week when Japan's Institute of Space and Astronautical Science launched an 8-meter radio telescope into an elliptical orbit that takes it from 990 kilometers to nearly 20,000 km away from Earth. On its own, the sensitivity of this lightweight device, a meshwork of gold-coated molybdenum wire, is nothing to write home about. But by observing radio sources in concert with an existing network of some 40 telescopes distributed across the planet, this space-based detector promises to provide astronomers with their sharpest view yet of the universe.

To attain such resolution, astronomers rely on a technique called very long baseline interferometry, which combines images from a group of widely separated telescopes to generate a single, high-resolution image. Astronomers began using large arrays of radio telescopes on the ground in the 1980s but have been limited by Earth's diameter. "Now . . . we will be able to break this barrier and see fine details of celestial objects that are beyond the reach of a purely ground-based telescope array," says Paul A. Vanden Bout, director of the National Radio Astronomy Observatory in Charlottesville, Va. With the addition of the Japanese telescope, the resolution of the network has tripled; it now has the sensitivity of a single telescope with a diameter about 2.5 times that of Earth. At that resolution, an observer in Los Angeles could discern a grain of rice in Tokyo.

The Very Long Baseline Space Observatory, as the new, internationally funded system is known, should begin operation in April, recording radio emissions at wavelengths of 18, 6, and 1.3 centimeters. The observatory is best suited to studying bright, compact sources, such as high-speed jets of gas shooting from the center of galaxies, quasars, and other phenomena thought to be fueled by black holes. James M. Moran of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., says the network will enable him to probe emissions from clouds of water molecules orbiting within one-hundredth of a light-year of the black hole believed to reside at the heart of the galaxy NGC 4258. Such clouds constitute cosmic masers-regions that emit intense radio emissions and often indicate sites of new star formation. Calculating precise distances to masers may give astronomers another tool for estimating the scale and age of the universe.