U.S., Soviets to Orbit Joint Radiotelescope : Space: The antenna dish will be tuned to distant galaxies and objects such as neutron stars. It will seek clues to the universe.

Inspired in part by a letter written by Nobel Peace laureate Andrei D. Sakharov just before his death, the United States has agreed to join the Soviet Union in operating the first orbiting radiotelescope, the two countries announced Thursday.

In a joint appearance, Vice President Dan Quayle and Soviet Ambassador Yuri V. Dubinin hailed the venture as a harbinger of a new era of cooperation between the world’s dominant space powers. Quayle called it a “significant step,” to be followed by a “fresh look at international cooperation and all of the options that will be available to us.”

Soviet officials plan to launch their Radioastron telescope into Earth orbit sometime between 1993 and 1995. Its 33-foot antenna dish will be tuned to distant galaxies and objects such as neutron stars and pulsars, which present intriguing clues about the nature of the universe.

Under the arrangement between the two countries, the United States will provide ground-based recorder terminals to receive and process data transmitted by the telescope. It also will make U.S. radiotelescope dishes in this country and in the Southern Hemisphere available to work in conjunction with the orbiting Soviet instrument.

American scientists will be asked to join Soviet colleagues in planning the two-to-five-year mission, including the selection of stars and galaxies to be studied.

Details regarding the use of U.S. radiotelescopes in the effort still are being worked out by the National Science Foundation and the National Radio Astronomy Observatory. But National Aeronautics and Space Administration officials said the use of American dishes will permit the orbiting Soviet instrument to make useful observations 90% of the time while it is on orbit, instead of 40% otherwise.

Seventeen other nations also are participating in the venture.

Previously, the most notable cooperative venture between the United States and Soviet space programs was in July, 1975, when an American Apollo spacecraft made an orbital rendezvous and docked with a Soviet Soyuz vehicle, allowing astronaut crews to exchange visits.

Soviet President Mikhail S. Gorbachev proposed in 1987 that the two countries cooperate in the exploration of Mars.

Last December, NASA Administrator Richard Truly received a letter from Sakharov, the famed Soviet physicist and political dissident, urging the United States to participate with the Soviets in the Radioastron project.

It was said to have been one of the last letters signed by Sakharov before he died last Dec. 14 from an apparent heart attack.

At the time, American space officials already were looking for potential cooperative undertakings with the Soviets. Truly referred the letter to the National Space Council. Quayle, the panel’s chairman, became interested and pursued it with Soviet officials.

The recording equipment the United States will provide for the Radioastron project already has been designed, and an export licensed has been obtained to ship four units to the Soviet Union for use in the project.

In addition to lending recording and processing equipment, the United States will make its tracking and data acquisition network around the world available to support the mission.

Quayle declined to speculate where the cooperative undertaking may lead, but he said the Bush Administration believes that the United States is “entering a golden era in relation to space exploration.”

The endeavor, Dubinin predicted, will be a “good and wonderful project,” the beginning of “a new phase” in U.S.-Soviet relations.