The recovery is yet another reversal of fortune for the Japanese spacecraft, which has been plagued with problems since its visit to asteroid Itokawa in 2005.
It landed on the asteroid twice in November of that year, but its pellet gun – designed to dislodge material for collection – failed to fire. After an episode where it spun out of control and temporarily lost contact with Earth, engineers regained control and set it on a course back home.
Scientists are still eager to see the spacecraft return to Earth in case some loose asteroid bits accidentally made their way into the collection chamber during the landings.
But Hayabusa has been hobbling home without the full use of its four ion engines, which ionise xenon gas and then use electric fields to accelerate the ions, providing a steady – though weak – thrust.
One engine broke down shortly after launch and a second quit in 2007. When a third gave up the ghost on 4 November, it looked like Hayabusa would have too little power to ever get home.
Charge buildup
But the mission team has now cobbled together another working engine using parts from two sick ones, the Japan Aerospace Exploration Agency (JAXA) announced on Thursday.
One engine is still able to spit out positive ions for thrust, but can no longer squirt out negatively charged electrons, a step needed to prevent electric charge buildup on the spacecraft. The team got around this by spewing the required electrons from a second sick engine that retains this ability.
Now that Hayabusa in effect has two working ion engines again, it is back on track to return to Earth in June 2010, as had been planned before the 4 November glitch, JAXA says. If all goes well, it will drop its sample capsule in the Australian outback.
But Hayabusa project manager Jun'ichiro Kawaguchi of JAXA cautions that no one knows how long the cobbled-together engine will last. "This new configuration is very new to us and we are not sure ... how much we can count on [it]," ( Scientist.com )
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