Asteroid sampler spacecraft could attempt trip home
BY STEPHEN CLARK
Posted: February 11, 2007
The star-crossed probe that attempted to retrieve the first samples from an asteroid in 2005 will soon embark on a three-year journey back to Earth, according to a senior mission official.
The voyage is currently expected to begin in late March, said Hayabusa project manager Junichiro Kawaguchi.
Tests are underway this month before controllers commit to the return, and officials are expressing caution since the probe has already suffered from several problems in its nearly four-year history.
At least two of Hayabusa's four ion engines are required for the journey, and engineers last tested the propulsion system in May 2006, Kawaguchi said.
"This is not an optimistic operation, but a very tough operation," Kawaguchi said. "The spacecraft is not in a very healthy state."
Hayabusa is believed to still be in the vicinity of asteroid Itokawa about 50 million miles from Earth.
"The biggest challenge in this mission is to demonstrate that we humans can make a round trip voyage to other celestial bodies," Kawaguchi said.
If successful, Hayabusa would usher in a new era in planetary exploration, he said.
"We lost chemical fuels and thrusters aboard. We had lost two (reaction) wheels already. The spacecraft lost the battery as well. But the operation team made a great effort to restore the spacecraft," Kawaguchi said.
After a series of problems struck the mission in late 2005, engineers were forced to postpone the start of the trip back to Earth by a year. Those issues included a fuel leak, a loss of communications and a botched sample recovery attempt.
Hayabusa spent three months near the potato-shaped asteroid in an attempt to study the space rock and then gather small samples from the surface during a series of daring close approaches.
Officials still don't know if bits of rock and dust are housed inside a protective chamber designed to plummet through Earth's atmosphere to a parachuted landing, but that is not stopping teams from trying to bring the craft home safely.
A pellet was supposed to be fired into the surface of Itokawa to force the rocks through a funnel to guide the precious samples into a container for the voyage back to Earth.
Those plans did not materialize in November 2005 and Hayabusa spent up to 30 minutes on the asteroid's surface during a failed retrieval attempt. Officials later reviewed telemetry data from a subsequent attempt and determined the pellet likely did not fire because the system was disarmed.
A sudden disturbance several weeks later cut off communications with the probe for more than six weeks and forced managers to postpone the start of the trip to Earth by a year.
Officials blamed the loss of communications on a chemical fuel leak, and ground stations later established contact with Hayabusa.
Since regaining communications with the spacecraft, controllers have worked to bake off leaked fuel believed to have been deposited on the exterior of the probe. Ground stations also uplinked new attitude control software to help save xenon propellant used by the ion propulsion system.
Ground teams also recently reconditioned Hayabusa's lithium batteries and closed the lid of the return capsule.