26 June 1995 Global astrometric interferometer for astrophysics (GAIA)
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GAIA represents a preliminary concept for an astrometric mission being considered in the context of ESA's `Horizon 2000 Plus' long-term scientific program. It comprises three stacked Fizeau interferometers viewing different directions within an instantaneous scanning circle, each interferometer consisting of two 50 cm aperture mirrors with a baseline separation of 2.5 m. Equipped with a modulating grid, and using CCDs, at least as the baseline detector, repeated scanning of the celestial sphere over a period of five years is estimated to lead to positions, proper motions, and parallaxes of some 50 million objects, down to about V equals 15 mag, with an accuracy of better than 10 microarcsec, along with multi-color multi-epoch photometry of each object. The scientific case for such a mission is compelling: distances and kinematical motions for objects throughout our Galaxy would be obtained, along with valuable information on the space-time metric ((gamma) ), angular diameters of hundreds of stars, and a vast body of information on double and multiple systems. Screening of all 100,000 stars within 100 pc for periodic photocentric motions would provide the most powerful and systematic method of detecting possible planetary companions proposed to date.
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Lennart Lindegren, Lennart Lindegren, Michael A.C. Perryman, Michael A.C. Perryman, Sacha Loiseau, Sacha Loiseau, } "Global astrometric interferometer for astrophysics (GAIA)", Proc. SPIE 2477, Spaceborne Interferometry II, (26 June 1995); doi: 10.1117/12.213006; https://doi.org/10.1117/12.213006

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