Japan's beleaguered
space probe Hayabusa, which may or may not have collected samples of an
asteroid, fired up its engine Wednesday to resume its trip back to Earth.
After more
than a year coasting through space, Hayabusa reignited its ion-powered
engine to begin the second leg of what has become an
extra-long trek home from the asteroid Itokawa, said officials with the Japanese
Aerospace Exploration Agency (JAXA).
"We are
continuing to pay careful attention to our onboard equipment and are doing our
utmost to operate the Hayabusa with the greatest care," JAXA officials said in
a mission update.
The
spacecraft is expected to return in June 2010 to deliver a sample canister that
will plunge through the atmosphere and land on Earth. Hayabusa would be the
first spacecraft to return samples from an asteroid, though past NASA
probes have collected samples from a comet and solar wind.
Hayabusa had
been flying in a silent coast mode since April 2007, when it officially began the
180 million mile (290 million km) trip home from Itokawa. The spacecraft
arrived at Itokawa in 2005, but suffered a series of glitches and malfunctions
that left flight controllers unsure whether it actually managed to
collect a sample of the asteroid's surface.
Hayabusa
also lost a smaller probe, dubbed Minerva, which was supposed to hop around
Itokawa's surface and take close-up pictures. The probe was
successfully deployed, but drifted off the asteroid's surface soon after, JAXA
officials said at the time.
While practice
landing attempts were plagued by glitches, Hayabusa did eventually
touch down on the potato-shaped asteroid. The spacecraft also photographed the asteroid throughout its mission.
Hayabusa
lost two of its three attitude-controlling gyroscopes during flight, with a
subsequent fuel leak and communications issues forcing mission managers to delay its return by three
years to June 2010.
Since its
launch in May 2003, Hayabusa's ion engine has operated for about 31,000 hours. Ion
engines accelerate spacecraft slowly by using electricity generated by
solar arrays to charge a stream of xenon gas. The resulting charged particles,
or ions, are then shot out a nozzle to generate thrust over time.
The method
allows spacecraft to fly farther with less fuel. NASA is using an ion drive on
its Dawn spacecraft, a probe that is en route to be the first to visit two
asteroids - Vesta and Ceres - in a single mission.
JAXA
officials said Hayabusa will continue to fire its ion drive until about March
2010, after which its trajectory will be refined for the planned June 2010
capsule return.
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