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Gaia: focus, straylight and basic angle


Author: Mora, A. · Biermann, M. · Bombrun, A. · Boyadjian, J. · Chassat, F. · Corberand, P. · Davidson, M. · Doyle, D. · Escolar, D. · Gielesen, W.L.M. · Guilpain, T. · Hernandez, J. · Kirschner, V. · Klioner, S.A. · Koeck, C. · Laine, B. · Lindegren, L. · Serpell, E. · Tatry, P. · Thoral, P.
Publisher: SPIE
Source:MacEwen, H.A.Lystrup, M.Fazio, G.G., Space Telescopes and Instrumentation 2016: Optical, Infrared, and Millimeter Wave, 26 June 2016 - 1 July 2016, 9904
Proceedings of SPIE - The International Society for Optical Engineering
Identifier: 573284
ISBN: 9781510601871
Article number: 99042D
Keywords: Electronics · Astrometry · Basic angle · Focus · Gaia · Interferometry · Stability · Straylight · Wavefront sensor · Adaptive optics · Convergence of numerical methods · Focusing · Interferometry · Space flight · Space telescopes · Mitigation schemes · Optimum performance · Root cause analysis · Wave front sensors · Working groups · Millimeter waves · High Tech Systems & Materials · Industrial Innovation · Nano Technology · SSE - Space Systems Engineering · TS - Technical Sciences


The Gaia all-sky astrometric survey is challenged by several issues affecting the spacecraft stability. Amongst them, we find the focus evolution, straylight and basic angle variations Contrary to pre-launch expectations, the image quality is continuously evolving, during commissioning and the nominal mission. Payload decontaminations and wavefront sensor assisted refocuses have been carried out to recover optimum performance. An ESA-Airbus DS working group analysed the straylight and basic angle issues and worked on a detailed root cause analysis. In parallel, the Gaia scientists have also analysed the data, most notably comparing the BAM signal to global astrometric solutions, with remarkable agreement. In this contribution, a status review of these issues will be provided, with emphasis on the mitigation schemes and the lessons learned for future space missions where extreme stability is a key requirement.