Hipparcos

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.

Objectives

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.

The instruments

* 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.

Catalogue

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.