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28 July 2000 High-precision space photometer: COROT
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Abstract
When the first exciting results of helioseismology were published little more than 20 years ago, the idea established soon to also apply this new tool to stars. Due to the extremely low photometric signal expected for solar type pulsation it was obvious to take advantage of the very low photometric noise level and inherent stability of space experiments, as well as of the possibility to obtain very long uninterrupted homogeneus data sets in space. Compared to what can reasonably be obtained from ground an improvement of the photometric accuracy of about two orders of magnitude is expected for such a space experiment, which, over all, will be obtained simultaneously for a relatively large number of stars. Despite these clearly identified advantages, it took some time for this new science field to be established in space programmes, as is illustrated by the history of COROT. The basic scientific concept dates back to 1981 when EVRIS (Etude de la Variabilité, de la Rotation et des Interieurs Stellaires) was proposed to CNES. The following year a similar experiment (PSIVA) was presented to ESA as a free-flyer mission, but complemented by instrumentation devoted to study stellar activities, and again in 1985 with European CoInvestigators as project PRISMA. The photometric section of PRISMA was proposed in 1987 as an experiment on the SOHO service module, but unfortunately, budget cuts and cost overruns caused a cancellation of all scientific experiments scheduled for this module. In parallel, implementations on EURECA-B were studied and as a small payload attached to the Space Station. At about the same time, EVRIS was proposed to the Sovjet Space Agency, IKI, as a photometric experiment on VESTA, a mission to asteroids, and (1986 to 1988) as a cruise-time experiment for MARS 92 and for MARS 94. Finally, end of 1988, EVRJS was accepted by IKI for MARS 94 and in 1990 by the main funding agency, CNES. While the EVRIS experiment was developed and optimized for the Mars mission, a study for a larger and more powerful follow-up mission started and lead to a concept called COROT (Convection, Rotation and Planetary Transits). The failure of the last stage of the MARS 96 launcher caused a total loss of all on board experiments, and hence also of EVRIS, but already few weeks later, CNES approved a study for COROT which was welcome with much relieve by the hitherto unlucky science team. For completeness, we have to mention that meanwhile two ESA calls for proposals of medium size missions were answered with participation of EVRIS science team members: 1989 to the M2-call with project PRISMA, a space experiment focussed on asteroseismology and stellar activities, and in 1993 to the M3-call with project STARS, specialized on asteroseismology and the detection of extrasolar planets. After fierce competition both projects were selected for full ESA Phase A studies, but lost the final selection for an ESA medium size mission. Only recently it has been realized that the same technique optimized for asteroseismology can also be efficiently used to search for extrasolar planets by observing the faible stellar luminosity decrease during the transit of a planet in front of the parent star. The requirements for such an ultra-high photometric precision put severe constraints on the instrument design, in particular on the stability, the elimination and/or control of a large variety of perturbations. COROT is the first project aiming simultaneously on asteroseismology and the detection of extrasolar planets. It has now fmished phase B and launch is planned for 2004. In the following we present a bibliography which should allow the interested reader to find a detailed description of most of the technical and scientific aspects of COROT, as well as some historical notes
© (2000) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Werner W. Weiss and Annie Baglin "High-precision space photometer: COROT", Proc. SPIE 4013, UV, Optical, and IR Space Telescopes and Instruments, (28 July 2000); https://doi.org/10.1117/12.394027
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