The European Space Agency's Rosetta spacecraft is alive and well as it continues orbiting Comet 67P.
However, orbiting a comet poses challenges that we don't see when orbiting planets and asteroids. Now that 67P is getting a bit closer to the sun, gases and dust are starting to stream out from the comet as its tail begins to form. Rosetta's orbit periodically takes it close to the comet, and right through that developing tail. The particles themselves aren't doing much to the spacecraft, but the reduced visibility IS causing problems.
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You see, Rosetta knows exactly where it is and stays on course by "seeing" and tracking certain stars. When those stars are obscured, it's sort of like a pilot flying into a cloud -- he or she can get disoriented.
The Rosetta operations team reports that two hours before the spacecraft's close approach on Feb. 14, Rosetta began to lose the ability to identify enough stars to track correctly, and occasionally locked onto "false" stars. This resulted in the spacecraft switching to some backup units (including its backup star tracker) in order to try and address the issue. However, the backup also subsequently experienced tracking problems due to the lack of stars in the field-of-view during the flyby.
"With a lot of luck, the spacecraft did not end up in ‘safe mode'," said Sylvain Lodiot, Rosetta spacecraft operations manager. "Although in this case we could have recovered the spacecraft and resumed operations as planned, the science instruments would have automatically switched off in the meantime. By the time they had been switched back on, we would have been relatively far away from the comet again."
"Doing science during a close flyby like this is not easy, and we are looking at ways to better prepare for future flybys so that we can maximize science while not jeopardizing the safety of the spacecraft," added Matt Taylor, ESA's Rosetta project scientist.
Indeed, the team are discussing plans to fly through one of the comet's jets this summer, taking into account the lessons learned from this first close flyby. It's going to be an exciting summer watching Rosetta as it watches 67P turn into the type of comet we envision whenever we think about comets.
I'll keep you posted as I receive more great images and science from the Rosetta science team!
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Latest images of Comet 67P from Rosetta spacecraft: