More detail on the Hayabusa return timeline
Posted by Emily Lakdawalla
22-04-2010 16:25 CDT
JAXA has issued a notice with a little bit more detail on the timeline for Hayabusa's return to Earth. Five Trajectory Correction Maneuvers are planned, one in a couple of weeks and the rest in the two weeks or so before the sample return on June 13 at 14:00 UTC.
Here's the posted timeline. The posted timeline included dates written as "about 7 days prior to reentry"; in the second column below I've calculated the corresponding calendar dates. I can imagine two reasons why JAXA wouldn't have posted it that way: first, each Trajectory Correction Maneuver (TCM) is not a brief event but rather spans many hours, possibly even more than a day, since they're being performed under low-thrust ion propulsion rather than chemical propulsion; and second, I assume this calendar could change, and being vague about dates gives them a bit of wiggle room before they have to issue corrections. But that doesn't stop me from calculating the probable dates of each event.
|Date (JAXA)||Date (ESL)||Event|
|March 27||Completed the second trajectory shifting by ion engines
That is, end of powered flight, beginning of reentry phase of mission)
|April 6||TCM-0 implemented the initial guidance to the outer rim of the Earth.
These first TCMs aim Hayabusa at Earth's limb so that it will continue into space if something bad happens)
|About 39 days prior to reentry||May 5||TCM-1 to guide to the outer rim of the Earth|
|About 15 days prior to reentry||May 29||TCM-2 to guide to the outer rim of the Earth|
|About 7 days prior to reentry||June 6||TCM-3 to guide to Australi
Finally, Hayabusa will be aiming for Earth)
|About 3 days prior to reentry||June 10||TCM-4 to guide to Australia (more detailed guidance)|
|About a day prior to reentry||June 12||Increase capsule temperature|
|About 3 hours prior to reentry||11:00 UTC||Capsule separation|
|Around 11:00 p.m. JST||13:00 UTC||Entry|
|One hour after reentry||14:00 UTC||Capsule landing|
I was amused to read the first lines of the JAXA update: "The Japan Aerospace Exploration Agency (JAXA) would like to announce that it was issued the Authorized Return of Overseas Launch Space Object (AROLSO) for the Sample Recovery Capsule aboard the Asteroid Explorer "HAYABUSA" from the Space Licensing and Safety Office (SLASO) of the Australian Government on Friday, April 16th." While I am sure that the Space Licensing and Safety Office existed prior to this exchange, it made wonder if said office had a stack of forms titled "Authorized Return of Overseas Launch Space Object (AROLSO)" lying around in a file cabinet for all those times when foreign countries plan to land spacecraft in the Outback. Maybe they're repurposing some existing bit of bureaucracy having to do with moving sensitive technology into and out of the country, like ITAR in the US. I don't know. But the bureaucratese struck me as funny.
JAXA is working hard to get news out about Hayabusa's return in English. There is a new English-language "Hayabusa: The Final Approach" website, as well as Hayabusa Live, a blog with mostly Japanese but occasional English-language posts. Finally, there is @Hayabusa_JAXA on Twitter, which is, again, mostly in Japanese but occasionally in English. Via Twitter, for instance, I learned that the round-trip radio communication time with Hayabusa is now only two minutes -- such a rapid response from a spacecraft gives the team a strong feel for how closely it is approaching Earth!