The Hipparcos Catalog (HIP) is a high-precision star catalog based on measurements by the Hipparcos astrometric satellite (active 1989-1993). With the publication of the measurement results in 1997, the mission brought astrometry a leap forward:
The fundamental catalog FK5 with 1500 stars, which was used as the basis for the most precise celestial coordinates ( star locations ) , was about 50 times more accurate. In 2000 the coordinate system was refined again (3300 stars of the FK6 ), so that the measurements of Hipparcos could be evaluated homogeneously over the whole sky.
The satellite was able to measure the star locations , parallaxes and movements of over 118,000 stars with a previously unattainable precision of about 0.003 "or 0.002" / year. In addition, a second instrument on board scanned over 1 million stars, the data of which was recorded with a still considerable ± 0.02 "in the 1997 Tycho-1 catalog . The 2000 Tycho-2 catalog is based on the same data basis.
The two catalogs formed the Hipparcos Celestial Reference Frame (HCRF) and were the best implementation of the International Celestial Reference Frame (ICRF) in the optical area when they were published . They now allow everyone to measure celestial objects with a telescope and digital camera precisely and semi-automatically . It was only with the publication of the Gaia Celestial Reference Frame based on the measurements of the Gaia mission that these results were exceeded.