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2005.12.15

Hayabusa in Salvation Mode

Today (14th) JAXA/ISAS hold a press briefing on Hayabusa. As usual, a space journalist Shin-ya Matsuura recorded the briefing on his blog. A collaborative translation is available on Wiki. Thank you Mishima, nao, HideoFukumori and hir for the real time efforts to make this information available to the World!

On the 8th, around 13:15 JST, the signal from Hayabusa gradually started to fade out. It lost the communication to the Earth on the 9th. JAXA/ISAS speculates the spacecraft is now in coning motion, exceeding the nutation angle. The reason for the loss of the attitude control is thought to be a discharge of the leaked propellant by about 8 to 10 cc. It gave the enough erroneous torque to surpass the recently established Xenon neutralizer attitude control scheme, and the spacecraft went out of control.

Hayabusa team needs to switch from the nominal operation to the salvation mode. They need to re-establish the communication before anything can be done. The spin dynamics of the spacecraft is such that the rotation will eventually converge around the Z-axis of the spacecraft.

The spin axis, once stabilized, must be in a certain angle between the Earth and the Sun, to regain the functionality. Probability for the spacecraft to stablize itself into such an angle is 60% by December 2006, and 70% by Spring 2007. The figures in JAXA press release gives the allowed region of the spin axis through December 2005 to March 2007. Starting the return leg in Spring 2007 will bring back the spacecraft to the Earth in June 2010.

The status of the thruster system was not recovered on the 8th. The new attitude control by Xenon gas will enable the return leg, though the operation of the ion engine becomes much more complex. The detail data on the second touch down attempt on November 25 is still not retrieved from the spacecraft.

If Hayabusa succeeds to come back to the Earth in 2010, it would become more than 7 years journey, well beyond its 4 years designed life span.

I agree with the Planetary Society Weblog.

The data they have returned already is invaluable and unmatched in the study of the small but potentially deadly population of bodies in near-Earth space, and their experience in controlling a spacecraft in the vicinity of such a tiny body is unique. They have accomplished a lot -- they deserve credit for that.
Thank you Emily. I myself feel kind of proud as a Japanese for their great achievement. Now I think it's about time to move on to the next step. JAXA should bring the asteroid mission to the forefront of Japanese space exploration, and design the improved spacecraft based on this invaluable experience. The team is, after all, only one of its kinds.

We should closely keep eyes on what they would have learned from this endeavor. Great achievement, yet lots have to be improved by next time. The very review process defines their future. The world is watching.

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