Recent images from the Japanese Aerospace Exploration Agency's Hayabusa probe to the asteroid Itokawa reveal a world that looks very much like a loosely held together pile of rubble.  But this junkpile isn't giving up its secrets easily--the mission has been problematic so far...

Asteroid "Itokawa"

Hayabusa (wiki) is supposed to touch down on the surface of Itokawa for a period of a second or two.  During that time it will fire a metal bearing into the surface, and collect the material ejected by the impact before lifting off again.  The collected material will be returned to Earth in 2007.  But landing on a rapidly tumbling 1800 foot long pile of rubble with an escape velocity of only 0.3 mph is tricky business.  So tricky in fact, that it is not possible to guide it remotely from Earth, therefore Hayabusa has an autonomous maneuvering system which handles the landing procedure and navigation near the asteroid.

The first attempted touchdown took significantly longer than ground control expected, and coincided with a loss of communications that lasted several hours.  Eventually JAXA controllers transmitted a command to the spacecraft to ascend to a higher altitude in order to find out what happened.  At present it isn't clear whether the probe touched down or not.  Another landing will be attempted on November 25.

Hayabusa carried a robot lander called "MINERVA".  This camera-equipped lander was touch down on the surface of the asteroid and move about by hopping from place to place.  Unfortunately, moments before the command to release the lander was received by the probe, the probe's autonomous navigation system decided the craft was drifting too close to Itokawa and fired thrusters to gain altitude.  Because Hayabusa was ascending when MINERVA was released, the little lander had the wrong trajectory and tumbled away into space instead of landing on the asteroid's surface.

At this time there is a remote chance that the effects of solar wind will push the lander back to the asteroid in a week's time, but MINERVA's batteries are not expected to last that long.

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