Session
Technical Session IX: The Year In Retrospect
Abstract
The MOST (Microvariability and Oscillations of Stars) microsatellite, launched from the Plesetsk Cosmodrome in Russia on June 30, 2003, has had a very successful first year in orbit. MOST is an astronomical science mission designed to measure brightness variations as small as a few parts per million in bright nearby stars. This application demands a pointing accuracy that is not normally associated with microsatellites. One requirement for the MOST mission was that the spacecraft point the boresight of the science instrument (a 15-cm optical telescope feeding a CCD camera/photometer) to an accuracy of 25 arcseconds. In practice, the MOST attitude control system (ACS) far exceeds expectations, achieving a pointing accuracy of between 3 and 5 arcseconds on a regular basis. The instrument reaches a photometric precision at least 25 times better than anything ever attained, from the Earth or space. This success did not come easily, but after a commissioning process that lasted about 5 months and had to overcome several unexpected hurdles. The most serious of these included an unexpectedly high level of stray Earthlight leaking into the instrument focal plane, and the corruption of 1 random block of RAM (of 32 in total) in the onboard computer, which was not recognized until well after launch. In this paper, the post-launch history of MOST will be described, with special emphasis on achieving the unprecedented ACS performance. Some of the exciting early scientific results, which in one case has overturned two decades of previous theory and observation, will also be summarized. The next instrument capable of matching the duty cycle and photometric precision of MOST will be the COROT satellite, a CNES mission due for launch in 2006. COROT represents a more conventional (hence, more costly) approach to this type of space science mission, and direct comparisons between COROT and MOST will be made.
Presentation Slides
The MOST Microsatellite Mission: One Year In Orbit
The MOST (Microvariability and Oscillations of Stars) microsatellite, launched from the Plesetsk Cosmodrome in Russia on June 30, 2003, has had a very successful first year in orbit. MOST is an astronomical science mission designed to measure brightness variations as small as a few parts per million in bright nearby stars. This application demands a pointing accuracy that is not normally associated with microsatellites. One requirement for the MOST mission was that the spacecraft point the boresight of the science instrument (a 15-cm optical telescope feeding a CCD camera/photometer) to an accuracy of 25 arcseconds. In practice, the MOST attitude control system (ACS) far exceeds expectations, achieving a pointing accuracy of between 3 and 5 arcseconds on a regular basis. The instrument reaches a photometric precision at least 25 times better than anything ever attained, from the Earth or space. This success did not come easily, but after a commissioning process that lasted about 5 months and had to overcome several unexpected hurdles. The most serious of these included an unexpectedly high level of stray Earthlight leaking into the instrument focal plane, and the corruption of 1 random block of RAM (of 32 in total) in the onboard computer, which was not recognized until well after launch. In this paper, the post-launch history of MOST will be described, with special emphasis on achieving the unprecedented ACS performance. Some of the exciting early scientific results, which in one case has overturned two decades of previous theory and observation, will also be summarized. The next instrument capable of matching the duty cycle and photometric precision of MOST will be the COROT satellite, a CNES mission due for launch in 2006. COROT represents a more conventional (hence, more costly) approach to this type of space science mission, and direct comparisons between COROT and MOST will be made.
