Hipparcos – Activities of the Input Catalogue Consortium

Abstract The Input Catalogue Consortium (INCA) is in charge of selecting the 100 000 stars to be observed by Hipparcos. In this paper the organisation of the Consortium is described, and the technical requirements to be met by the Input Catalogue for optimal scientific return are summarised. The various tasks of this long collective work are then reviewed including the identification process of the proposed stars, the progressive construction of a list without redundancies, and the definition of the ‘survey’. The final selection of the stars which will be observed by Hipparcos is being made using a numerical simulation which takes into account the observing constraints of the satellite, and a parameter called the ‘pressure’ which is calculated for each star. Finally, the organisation of working groups set up to deal with special objects (multiple stars, variable stars, minor planets, stars in dense areas, and stars for linking the Hipparcos system to an extragalactic reference system) are described. New photometric and astrometric programmes undertaken for stars with unsatisfactory precision on magnitudes and/or coordinates, a major part of the Consortium’s work, will be presented elsewhere.