The Hipparcos and Tycho Catalogues

This chapter describes various aspects of the Hipparcos and Tycho Catalogues useful for understanding the scientific exploitation considered in subsequent chapters. It describes some of the satellite measurement principles relevant for an understanding of the catalogue contents; the published intermediate astrometry data; details of the adopted reference frame; basic transformations relevant to catalogue users; details of the Tycho 2 Catalogue construction; error assessment; and details of associated data such as radial velocities and cross-identifications.