Three different problems apparently were to blame for throwing the Magellan Venus probe into protective hibernation Thursday, including a computer glitch and confusion about its location in space, officials said Saturday.
Project managers now believe it may take 10 days to two weeks to fully understand the problems, transmit corrective computer programming and resume testing of Magellan's critical radar system, the centerpiece of a $551 million project to Earth's sister planet in unprecedented detail."Nobody thinks they have a fatal problem," said Mary Beth Murrill, a spokeswoman for the Jet Propulsion Laboratory. "They even think they may be able to begin mapping, possibly on schedule, around Sept. 1."
Resuming operations with Magellan is crucial to the space agency, which has suffered through a storm of media and congressional criticism this summer over the flawed Hubble Space Telescope and problems with the shuttle program.
JPL engineers lost touch with Magellan on Thursday, but they were able to re-establish radio contact late Friday. With the probe's antenna locked firmly back on Earth, engineers spent the day Saturday sifting through reams of data from the solar-powered spacecraft.
Preliminary results indicate three apparently unrelated problems contributed to putting Magellan into various levels of protective hibernation called "safe modes."
Contact with Magellan was lost shortly after Magellan attempted to find and lock onto a guide star. Such "star calibrations" are part of a routine procedure to update on-board computers about the spacecraft's orientation in space.
Steve Wall, a Magellan engineer at JPL, said Saturday the safe mode programs apparently were activated when the computer that controls the spacecraft's attitude suddenly stopped sending routine timing signals to Magellan's master computer.
This loss of the first computer's "heartbeat" prompted the main computer to put the spacecraft into an initial safe mode called "RAM safing."
The spacecraft immediately stopped what it was doing, aimed its solar panels broadside to the sun and began to search for the bright star Sirius. By knowing its position relative to the sun and Sirius, Magellan would be able to point a radio antenna at Earth to receive further instructions.
At that point, the second problem occurred.
"What seems to have happened . . . is that it located something it thought was Sirius but was not," Wall said.