Hipparcos was the first space astrometry mission (astrometry is the precise measurement of the positions of stars). It was accepted by the ESA in 1980 and launched by Ariane on 8 August 1989.
Its objectives were to:
* Map the sky with unprecedented accuracy (0.002'', which would make it possible to see a man on the Moon from the Earth);
* Predict the impacts of the Shoemaker-Levy 9 comet on Jupiter;
* Identify stars that will pass close to the Sun;
* Establish the distance of stars with planets;
* Confirm Einstein's prediction of the effect of gravity on starlight.
* A Schmidt telescope with a 290 mm aperture and a focal length of 1400 mm, able to look in two directions at once at an angle of exactly 58°;
* An analysis grid, coupled to CCD cells;
* Two starmappers.
Following an apogee engine failure, the satellite was unable to move into geostationary orbit as initially planned. However, it sent data for 37 months (November 1989 – March 1993) and provided valuable information on 118,000 stars in the Milky Way. These were published in a catalogue in 1997.