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The Planetary Society Blog

By Emily Lakdawalla

Hayabusa Update: Hayabusa is alive; the target marker was placed successfully; another try in a few days

Weblog Archive

Sometimes it helps to stay away from a developing story for several hours -- things become much clearer. It also helps when a good person steps in to provide a superior translation of Japanese information!

Yesterday I was getting most of my information from the official Hayabusa weblog while the mission was proceeding nominally, which was true until Hayabusa reached an altitude of 90 meters. That weblog abruptly stopped at that point, and I found another one, from a Mr. Matsuura Shin, who seems to be a journalist who was sitting in the press room in Tokyo, reporting in Japanese on the statements being made by Professor Matogawa, the Director of JAXA's Space Education Centre. Overnight, a fellow called Mr. 5thstar has posted English translations of Matsuura Shin's weblog that are far superior to what Google could produce. Thank you, Mr. 5thstar!

So, to summarize:

• The target marker carrying the signatures separated from the spacecraft at 04:55 JST / 19:55 UTC at an altitude of 40 meters, and by their calculations it hit Itokawa 400 seconds later.
• The spacecraft took pictures of the marker and followed it autonomously, 'which went very well.' It was descending using its laser range finder.
• It descended to 17 meters, at which point the spacecraft had to rotate to 'align itself to the surface of Itokawa.' At this point high gain antenna communications had to stop, I assume because the rotation of the spacecraft brought the antenna out of line with Earth. The spacecraft switched to beacon mode; this means there was no live telemetry being returned, only a carrier signal to allow Doppler tracking.
• The spacecraft had been descending at 2-3 centimeters per second. JAXA conjectures that the spacecraft descended to within about 10 meters and then did not descend any further for about half an hour, though it may have been drifting horizontally with respect to the surface. 'Combined with other data, we do not think Hayabusa had touched down.'
• The spacecraft was not designed to stay so close to Itokawa for so long. The sunlit side of Itokawa is at about 100 degrees C. In close proximity to Itokawa, Hayabusa began to heat up.
• Finally, controllers sent the command to Hayabusa to abort the descent, to ascend and go into safe mode. Hayabusa appeared not to respond.
• However, at around the same time, something happened to cause the angle between the Sun and the solar arrays to get too large, which triggered an autonomous safe mode condition.
• The spacecraft ascended at 'rather high speed' and is now about 100 kilometers away from Itokawa. It will take several days for Hayabusa to return close enough to Itokawa to try again, after controllers have re-established complete control of the spacecraft.
• Also, while in safe mode the spacecraft entered a spin-stabilized condition. Before they can attempt to descend again they need to re-establish 3-axis stabilization, which appears not to have been accomplished yet.