Surveying the sky

An astrometric experiment in 1925 was the beginning of a development, which astronomer Erik Høg at the Niels Bohr Institute further developed from 1960. He devised a new method for accurate measurement of the stars in the sky that led ESA to launch the first major astrometry satellite Hipparcos in 1989. A scientific highlight is the star catalogue Tycho-2 from the year 2000, which describes the positions and movements of 2.5 million stars and is now absolutely essential to controlling satellites and for astronomical observations.