Stardust update: Almost to Tempel 1
Posted by Emily Lakdawalla
10-02-2011 11:06 CST
We're coming up on the final days of Stardust's approach to Tempel 1. The flyby takes place on February 15 at 04:56 UTC (February 14 at 20:56 PST). There's still time to enter the "Are We There Yet?" contest and win a Stardust T-shirt! In an update posted Tuesday, the mission confirmed the success of the most recent trajectory correction maneuver. An update posted yesterday contains some more details of the plans for the flyby than I've seen before.
For instance, there's further detail on what's likely the biggest challenge facing Stardust for this encounter: it's running on fumes. Project manager Tim Larson is quoted as saying that "We estimate we have a little under three percent of the fuel the mission launched with," but that this is only "an estimate, because no one has invented an entirely reliable fuel gauge for spacecraft." One way they do the estimates is by counting up all the thruster firings and adding up how much fuel they think they used. Well, they counted and they came up with half a million times that Stardust has fired its thrusters. Apart from the fact that that's a staggering number, it also makes clear why the mission can't be entirely sure how much fuel is left. It doesn't matter how precisely you measure your fuel consumption; after half a million thruster firings, rounding uncertainties can add up and make you unsure of the amount that's left.
There's also some detail on what the science plan is, and when we can expect to see data.
A few hours after the encounter on Monday, Feb. 14, at about 8:56 p.m. PST (11:56 p.m. EST)...the first of 72 bonus-round images of the nucleus of comet Tempel 1 [will be] downlinked. All images of the comet will be taken by the spacecraft's navigation camera -- an amalgam of spare flight-ready hardware left over from previous NASA missions: Voyager (launched in 1977), Galileo (launched in 1989), and Cassini (launched in 1997). Each image will take about 15 minutes to transmit. The first five images to be received and processed on the ground are expected to include a close up of Tempel 1's nucleus. All data from the flyby (including the images and science data obtained by the spacecraft's two onboard dust experiments) are expected to take about 10 hours to reach the ground.
A schedule provided to the media includes the following timeline:
8:30 to 10 p.m., Feb. 14 PST [04:30 to 06:00 Feb. 15 UTC]: Live NASA TV commentary begins from mission control; includes coverage of closest approach and the re-establishment of contact with the spacecraft following the encounter.
Midnight to 1:30 a.m., Feb. 15 PST [08:00 to 09:30 UTC]: NASA TV commentary will chronicle the arrival and processing of the first five of 72 close-approach images expected to be down linked after the encounter. The images are expected to include a close-up view of the comet's surface.
10 a.m., Feb. 15 PST [18:00 UTC]: News briefing
I think I plan to watch the late-night events on NASA TV from the comfort of my own couch, but will be at JPL for the February 15 press briefing.
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