December 27, 2006

COROT all set to begin science mission

After opening its protective cap and acquiring its 1st image 2 weeks ago, COROT is now in fine-pointing mode, the last crucial step before it starts returning science data.
2 February 2007
Tuesday 30 January, attitude data calculated by the instrument were used for the 1st time to finely control the satellite bus and achieve perfect boresight stability. Results exceeded all expectations, yielding a boresight accuracy of 0.3 arc seconds, more than 1.6 times better than the original specification of 0.5 arc seconds.

The optical performance of the seismology channel is already excellent. While acquiring images for calibration, COROT detected its 1st stray object: a piece of debris from a Delta 1 rocket launched in 1984, which left an easily identifiable track on the CCD in the middle of the star background. The object’s trajectory in the image exactly matches that calculated by NORAD (North American Aerospace Defense Command).

COROT then acquired its 1st images on the exoplanet channel on the night of 31 January to 1 February. Needless to say, they were eagerly awaited by the many exoplanet specialists gathered together at CNES for the occasion. Scientists are now poring over the images to plan future observations. The science mission can therefore begin as planned within the next 48 hours.

First light revisited

“First light” is a rather poetic way of describing what, in fact, is a vital step in the life of any ground- or space-based telescope. The quality of the 1st data collected enables engineers to gauge the instrument’s overall performance, the result of a finely tuned interplay between the detector, optics and platform.

So, not surprisingly, the atmosphere in the main mission control room on Wednesday 17 January was a mixture of tension and anticipation. “Emotions were running almost as high as for the launch,” says Laurent Boisnard, COROT System Manager.
“The image was taken at the edge of COROT’s field of view, in a direction where we were expecting to see the most stray light from Earth. The baffle’s attenuation performance was excellent, letting through only a minimal amount of stray light into the focal plane.”
The team is now looking forward to confirming these initial results in April, when the Sun will be close to the orbital plane.

All critical steps completed

The opening of the protective cap and first light were the last critical steps for the COROT project, and all systems have now checked out successfully. “We may still encounter some software glitches,” cautions Laurent Boisnard. “But we can reprogram software if needed. We now know for sure that everything on the satellite is working well.”

Opening of the protective cap. Crédits: CNES .

Although confident, COROT’s mission managers aren’t dropping their guard. During the night of 20 and 21 January, Satellite Manager Martine Jouret and Onboard Systems Engineer Eric Jurado were pulled out of bed at 1.00 in the morning. They soon located the problem: ground software had wrongly interpreted a week-change signal from COROT’s GPS receiver. We can wager that in a world where everything operated as smoothly as COROT since its launch, the passing of time would be the last anomaly to be corrected …

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