Speaker: Erik Høg, Niels Bohr Institute, Copenhagen University

Title: Hipparcos - Roemer – Gaia

ABSTRACT: During the Hipparcos space astrometry mission in September 1992, I presented a concept for using direct imaging on CCDs in scanning mode in a new and very powerful astrometric satellite, Roemer. The Roemer concept with larger aperture telescope for higher accuracy was developed by ESA and a mission was approved in 2000, expected to be a million times better than Hipparcos. The name Gaia mission reminds of an interferometric option also studied in the period 1993-97, and this period is a main subject of my presentation which also gives an overview of the two missions Hipparcos and Gaia.