Magellan Has JPL Scratching for Answers

To perplexed scientists Thursday, the Magellan spacecraft looked a little like a wayward waif, trying to ingratiate itself with an angry parent. Computer data sent back by the troubled Venus Radar Mapper revealed that after it lost contact with ground controllers Tuesday night, it fired its small jets over and over, trying to compensate for various problems, real or imagined.

“It got in trouble nine times,” said Steve Wall, a scientist at the National Aeronautics and Space Administration’s Jet Propulsion Laboratory. “Or at least it thought it was in trouble.”

As a result, the spacecraft burned a “tremendous amount” of fuel--more than five pounds--as it went through nine different maneuvers. That loss of fuel poses some concern for engineers at the Pasadena lab, who expect the craft to remain in orbit around Venus for up to two years, but Wall said Magellan still has plenty of fuel aboard for the remainder of its assignment.

“It’s not an immediate problem,” he said. The craft, which carries a radar camera capable of peering through the dense clouds that hide the surface of the planet, had 293 pounds of fuel aboard when it was launched toward Venus from the space shuttle last year.

What appeared to be the biggest problem Thursday was figuring out what went wrong after the spacecraft reached Venus. Magellan has broken communications with controllers twice since it went into orbit around the Earth’s sister planet earlier this month--on Aug. 16 for 14 hours, and again on Tuesday for 17 hours.

Engineers had hoped that they were dealing with a single problem that caused both shutdowns, but Wall said Thursday that does not appear to be the case.

The most recent loss of communications, during which Magellan went through nine separate maneuvers, had “a lot of different earmarks” than the earlier one, Wall said.

That suggests that the spacecraft, cornerstone of a $750-million Venus mission, may have more than one problem.

Engineers and scientists at JPL met all day Thursday, sorting through information that Magellan is sending back “very slowly,” Wall said.

The good news was that the spacecraft itself seems to be healthy.

The bad news was that no one could figure out why it breaks its communications link with the Earth and assumes a “safe mode” designed to ensure that its solar energy panels point toward the sun and its antenna sweeps past the Earth periodically, making it possible for engineers at JPL to regain control.

Officials said they will take whatever time is needed to be sure they understand Magellan’s problems before ordering the spacecraft to begin its comprehensive mapping of Venus. They had planned to begin that this weekend, but that is likely to slide several days because of the continued problems with the craft.