The Hipparcos Mission

Abstract

A review is presented of the European Space Agency's astrometric satellite project Hipparcos, for which the final data catalogues were published in June 1997. The emphasis is on those aspects that have or may have influenced the data as presented in the catalogues. It presents a brief review of the satellite, the aims of the mission with their relation to ground-based astrometry, and the mission history. This is followed by a description of the input data streams and a summary of the data reductions. Data files presented in the catalogues are described in the context of the data reductions, and explained in content and usage. The mission results comprise not only outstanding astrometric data on both single and double stars, but also an unique all-sky photometric survey which has been used for variability investigations. This has led to the discovery of thousands of variable stars. The Hipparcos mission was complemented by the Tycho experiment, providing a complete all-sky survey of astrometric and photometric parameters for one million stars down to magnitude 11, though with lower accuracies than obtained for the main mission. Astrometric and photometric data for a selection of 48 minor planets, the Jovian moon Europa and the Saturnian moons Titan and Iapetus were also obtained. The data quality verifications are reviewed and guidelines to the proper use of the Hipparcos data are provided, followed by some of the first scientific results of the mission. Experiences gained with this first ever space astrometry mission are considered in relation to a follow up mission for Hipparcos.