In spite of severe limitations in size and technology, the Hipparcos mission was remarkably efficient in providing an accurate reference frame and absolute parallaxes en masse. Combined with a larger telescope and modern CCD detectors, this concept for global astrometry could yield orders-of-magnitude improvements in accuracy, number of objects and sensitivity. Such considerations have lead to the definition of GAIA, a global astrometric satellite currently studied by the European Space Agency as a candidate for a Cornerstone mission with possible launch in 2009. With an accuracy in the 5 to 300 microarcsec range for 1000 million objects down to the 20th magnitude, the science goals of GAIA are primarily concerned with the origin, evolution and structure of the Milky Way galaxy and its satellite galaxies. The technical status of the project is outlined. It is shown why a single optical aperture is better for a scanning satellite than the originally proposed twin pupil of a Fizeau interferometer.
Lennart Lindegren: Hipparcos and the future: GAIA. In: Peter Brosche, Wolfgang R. Dick, Oliver Schwarz, Roland Wielen (Eds.): The Message of the Angles - Astrometry from 1798 to 1998. Proceedings of the International Spring Meeting of the Astronomische Gesellschaft, Gotha, May 11-15, 1998. (Acta Historica Astronomiae ; 3). Thun ; Frankfurt am Main : Deutsch, 1998, p. 214-222.
Html-Version: Wolfgang R. Dick. Created: 21 Jan 1999