Associated Press
Wednesday, July 29, 1998; Page A06

Engineers have made radar contact with a crippled satellite sent up to observe the sun, but are unable to establish a radio link because the satellite apparently has no electrical power, NASA officials said yesterday.

Radio signals from the Solar and Heliospheric Observatory (SOHO) satellite, a joint U.S. and European project, were abruptly interrupted June 24. Engineers have been trying since to find a way to reestablish contact with the craft.

SOHO was located by beaming signals from the 990-foot radio telescope at Arecibo, Puerto Rico. The signals apparently bounced off the satellite, which is about 1 million miles from Earth, and the echo was detected by NASA's deep space tracking dish in Goldstone, Calif. The technique worked like a radar, giving more than hour's worth of tracking data.

Preliminary analysis suggests the craft is spinning at the rate of about one revolution per minute, the officials said. It is still located where it was supposed to be, a spot where the gravity forces are stable and an object will not change its position relative to Earth.

Engineers believe SOHO is spinning with its solar power panels edge-on toward the sun, said Don Savage, a NASA spokesman. In this position, he said, the panels do not generate the power needed to recharge SOHO's batteries.

However, as Earth moves about the sun, the angle of the solar panels will change favorably, allowing them to capture more and more sunlight. It is hoped that within about 90 days the solar panels will be able to generate enough power to recharge the batteries, permitting the satellite to respond to radio signals from Earth, he said.

SOHO's battery can retain only a one-hour charge. That means the craft must generate electricity with its solar panels almost constantly to operate effectively.

What caused the sudden loss of radio signals is unknown, but is being investigated by a board of NASA and European Space Agency engineers.

SOHO has already completed its primary mission, but NASA and ESA engineers hoped to get additional research from the solar observatory.

The craft was designed for a two-year operational lifetime and was launched Dec. 2, 1995. NASA funded $477 million of SOHO's nearly $1 billion cost. ESA paid the rest.