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2005.11.23

Detail of the first touch down by Hayabusa

Translation of a part of Matsuura’s blog:

JAXA/ISAS analyzed the date downloaded from the spacecraft. Hayabusa detected an obstacle just below the altitude 17m, when it changed the orientation of the spacecraft towards the surface of Itokawa. At that point the high gain antenna moved away from Earth and the real time communication was lost.

Software onboard Hayabusa tried to go into the emergency take off but the orientation of the spacecraft was too steep (to what?) so it did not take off. It continued the free fall descent and bounded twice on the surface, according to the LRF data and the attitude data. Because the obstacle sensor had been triggered, the sampler horn was not engaged, so the impacter was not deployed. The event happened during the switch over from NASA Goldstone station to Usuda station, so they did not confirm the landing from the Doppler data.

The spacecraft was seemingly at rest with the sampler horn and an edge of the body or a solar panel wing attached to the surface.

The first touch down occurred around 6:10. The second touch down was around 6:30 after a bounce. Another small bounce brought the spacecraft into rest, according to the LRF data.

It stayed on the surface for 30 minutes, all the while it was being heated up by thermal radiation from the surface of Itokawa. Take off was performed by a command from Earth at 6:58, then entered into the safe mode.

JAXA/ISAS is still downloading the data. They might find more news on the rest of the data. No significant damage to the spacecraft has been confirmed, but some heater sensor needs some checkup.

And here is another article:

Matsuura interviewed Prof. Matogawa, an Associate Executive Director of the JAXA Public Affairs Office, over phone.

They did not study the possibility of the bouncing before the data is downloaded. It is natural that it bounced with the velocity of 10 cm per second where the escape velocity of the asteroid was 15 cm per second.

[...wait a minute! It braked to 4 cm per second at the altitude 40 m to release the target marker, isn't it??? ]

It seemingly landed just like a dog sits down. No leaning to sideways.

Some sand should come up at the impact of the touch down. Part of them should have reached to the sampler capsule. The capsule was programmed to be closed according to the sequence of the touch down, so it is still open now. Scientists insist on closing the capsule, so they will send the closing command in the next communication window tomorrow. There are several capsules on board for two scheduled touch down operations.

Currently Hayabusa is approaching to Itokawa at 4 km per hour. As it closes up, it slows down for delicate positioning. It depends on whether they can bring it back to the starting position, and also on the stamina of the operation team members, to have the second attempt on the 25th.

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