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Thrusters Fire on Ulysses as NASA Prepares Shuttle for Trip to Florida

October 12, 1990

PASADENA, Calif. (AP) _ The Ulysses solar explorer fired its thrusters and zoomed farther from Earth, while the shuttle that launched the spacecraft was readied for next week’s piggyback jet ride home to Florida.

NASA, meanwhile, formed a team to investigate why the shuttle Discovery lifted off Saturday with incorrect instructions for how it should operate some of its computer programs.

Ulysses’ two-day series of thruster firings were to end this afternoon. The maneuver was designed to turn Ulysses so its main antenna dish pointed toward Earth, allowing faster communication with controllers.

The $250 million spacecraft, which will explore the sun’s polar regions in 1994-95, is the centerpiece of a $750 million joint mission by NASA and the European Space Agency.

Since it was launched from Discovery on Saturday, Ulysses has been communicating with its controllers through one of its smaller antennas.

Discovery landed Wednesday at Edwards Air Force Base, Calif. Maintenance crews found Discovery in excellent condition after its 1.7-million-mile, four- day flight, said shuttle processing manager Tip Talone.

He said only 10 to 15 of Discovery’s heat-shield tiles need to be replaced. Debris that hit the shuttle during its launch and landing caused 13 ″dings″ larger than one inch, and about 50 smaller ones.

″That’s a very low number,″ Talone said. ″Every time we come back, we seem to learn more about how to fly and land the thing without taking a lot of hits.″

Talone said Discovery should be ready for a one-day flight back to its Cape Canaveral, Fla., launch site on Monday, riding piggyback on a modified jumbo jet.

Shuttle project engineer Chris Fairey said Thursday that the incorrect instructions were loaded into one of Discovery’s computers Oct. 4. The investigators will recommend steps to prevent such an error from happening again, he added.

The incorrect instructions were noticed and fixed by Discovery’s five astronauts about an hour after the shuttle was launched.

They never posed a danger to the shuttle or its crew - even if the error hadn’t been detected, said Milt Heflin, lead flight director at Johnson Space Center in Houston.

Heflin said NASA considered the problem serious because it went undetected before Discovery was launched. Fairey called it ″really minor″ but said it ″did point out a minor deficiency in the way we code our software.″

Ulysses was 3.68 million miles from Earth on Thursday, zipping toward a 1992 flight past Jupiter at 25,372 mph, said Franklin O’Donnell, a spokesman at NASA’s Jet Propulsion Laboratory. Ulysses will use Jupiter’s gravity to sling it into orbit around the sun.

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