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Abandoned Soviet Space Station to Fall to Earth : Salyut-7: Parts of the craft are expected to survive fiery descent. It has had a troubled history.

TIMES SCIENCE WRITER

An abandoned 43-ton Soviet space station is expected to tumble out of orbit around Feb. 8, and parts of it probably will survive a fiery plunge through the atmosphere and hit Earth, according to space experts.

Most of the 9-year-old craft, called Salyut-7, is expected to burn up before it hits the ground, but “we believe some of the station will survive re-entry,” said David Rourk, a duty officer with the U.S. Space Command in Colorado Springs, Colo.

The station is in a rapidly decaying orbit that carries it over most of the globe--from 51.7 degrees north to 51.7 degrees south, which includes most of North America. At this time no one knows where the debris will land or exactly when it will come down, Rourk said in a telephone interview.

“The most accurate prediction will come 12 hours prior to re-entry,” he said. At that time, the Space Command will notify the U.S. State Department and the Federal Emergency Management Agency and more detailed warnings will be issued.

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It is impossible to predict the exact time this far in advance because the decaying orbit is influenced by atmospheric drag, which in turn is somewhat dependent on solar storms which can increase the density of the upper atmosphere. And no one knows where the station will land because it is out of control.

The 45-foot-long station weighs 21 tons and is attached to a 22-ton module, called Kosmos-1686, which docked with Salyut-7 six years ago. The attachment most concerns some officials because it is a “descent module” designed to survive re-entry.

The module “should not burn up in the atmosphere and did not burn up when it underwent tests,” a Soviet official said during a recent television news program in Moscow. He called that situation “extremely unpleasant,” but he added quickly that experts “look upon the forthcoming meeting (of the debris) with the Earth rather optimistically.”

That optimism is based on the fact that most of the Earth is covered by ocean and much of the land is sparsely populated, so the chance of anyone being hurt is not considered great.

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Salyut-7 was supposed to last at least another eight to 10 years, the officials said during the broadcast, then it was to return to Earth aboard the Soviet space shuttle, called Buran. But the Buran has flown only in an experimental unmanned configuration, and there is considerable doubt that it will ever fly again.

The fiery end to Salyut-7 will be the final chapter in the troubled history of the station. It malfunctioned while it was unmanned in 1984, and Soviet officials did not think they would be able to repair it. But a year later spacewalking cosmonauts salvaged the station and it resumed operations. Its functions have since been taken over by the Soviet Union’s newer space station, Mir.

Salyut uses small rockets to maintain its orbit, but they no longer are able to compensate for atmospheric drag. In its final hours the station is expected to begin tumbling, which will slow it down dramatically and drop it out of orbit.

Other spacecraft have tumbled to Earth with minimal effects, although there have been some anxious moments. Most notable is the United States’ only manned space station, Skylab, which plunged through the atmosphere in 1979 and littered parts of Australia with debris.

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