Hipparcos

Hipparcos

Hipparcos satellite in the Large Solar Simulator, ESTEC, February 1988
Names	HIPPARCOS
Mission type	Astrometric observatory
Operator	ESA
COSPAR ID	1989-062B
SATCAT no.	20169
Website	http://sci.esa.int/hipparcos/
Mission duration	2.5 years (planned) 4 years (achieved)
Spacecraft properties
Spacecraft	HIPPARCOS
Manufacturer	Alenia Spazio Matra Marconi Space
Launch mass	1,140 kg (2,510 lb) [1]
Dry mass	635 kg (1,400 lb)
Payload mass	210 kg (460 lb)
Power	295 watts
Start of mission
Launch date	8 August 1989, 23:25:53 UTC
Rocket	Ariane 44LP H10 (V33)
Launch site	Centre Spatial Guyanais, Kourou, ELA-2
Contractor	Arianespace
Entered service	August 1989
End of mission
Disposal	decommissioned
Deactivated	15 August 1993
Orbital parameters
Reference system	Geocentric orbit[2]
Regime	Geostationary transfer orbit Geostationary orbit (planned)
Perigee altitude	500.3 km (310.9 mi)
Apogee altitude	35,797.5 km (22,243.5 mi)
Inclination	6.84°
Period	636.9 minutes
Revolution no.	17830
Main telescope
Type	Schmidt telescope
Diameter	29 cm (11 in)
Focal length	1.4 m (4 ft 7 in)
Wavelengths	visible light
Transponders
Band	S-Band
Bandwidth	2-23 kbit/s
Legacy ESA insignia for the Hipparcos mission

Hipparcos was a scientific satellite of the European Space Agency (ESA), launched in 1989 and operated until 1993. It was the first space experiment devoted to precision astrometry, the accurate measurement of the positions of celestial objects on the sky.^[3] This permitted the first high-precision measurements of the intrinsic brightnesses (compared to the less precise apparent brightness), proper motions, and parallaxes of stars, enabling better calculations of their distance and tangential velocity. When combined with radial velocity measurements from spectroscopy, astrophysicists were able to finally measure all six quantities needed to determine the motion of stars. The resulting Hipparcos Catalogue, a high-precision catalogue of more than 118,200 stars, was published in 1997. The lower-precision Tycho Catalogue of more than a million stars was published at the same time, while the enhanced Tycho-2 Catalogue of 2.5 million stars was published in 2000. Hipparcos' follow-up mission, Gaia, was launched in 2013.

The word "Hipparcos" is an acronym for HIgh Precision PARallax COllecting Satellite and also a reference to the ancient Greek astronomer Hipparchus of Nicaea, who is noted for applications of trigonometry to astronomy and his discovery of the precession of the equinoxes.