The Hipparcos satellite was launched by the European Space Agency (ESA) in August 1989. After some initial problems with a boost motor, the satellite began its mission November that year.

The objective of the Hipparcos mission was the production of a star catalog of unprecedented accuracy. Based on a predetermined set of 120,000 stars of magnitudes down to 13, the satellite gathered detailed information about astrometric position, parallaxes (down to one milli-arc-second), as well as proper motion data (down to two milli-arc-seconds).

The measurements was produced by an Image Dissector Tube (IDT), which sampled the modulated signal produced by a star crossing the fine grid slits located in the focal plane of the payload telescope.