Tycho Catalogue
Hipparcos satellite in the Large Solar Simulator, ESTEC, February 1988
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| Mission type | Astrometric observatory |
|---|---|
| Operator | ESA |
| COSPAR ID | 1989-062B |
| SATCAT no. | 20169 |
| Website | sci |
| Mission duration | 4 years, 1 week |
| Spacecraft properties | |
| Manufacturer |
Alenia Spazio Matra Marconi Space |
| Launch mass | 1,140 kg (2,510 lb) |
| Dry mass | 635 kg (1,400 lb) |
| Payload mass | 210 kg (460 lb) |
| Power | 295 watts |
| Start of mission | |
| Launch date | 23:25:53, August 8, 1989 |
| Rocket | Ariane 4 44LP (V-33/405) |
| Launch site | Kourou ELA-2 |
| Contractor | Arianespace |
| End of mission | |
| Disposal | decommissioned |
| Deactivated | August 15, 1993 |
| Orbital parameters | |
| Reference system | Geocentric |
| Regime | Geostationary transfer orbit |
| Semi-major axis | 24,519 km (15,235 mi) |
| Eccentricity | 0.720 |
| Perigee | 500.3 km (310.9 mi) |
| Apogee | 35,797.5 km (22,243.5 mi) |
| Inclination | 6.84 degrees |
| Period | 636.9 minutes |
| RAAN | 72.93 degrees |
| Argument of perigee | 161.89 degrees |
| Mean anomaly | 250.97 degrees |
| Mean motion | 2.26 rev/day |
| Epoch | 16 June 2015, 13:45:39 UTC |
| Revolution no. | 17830 |
| Main telescope | |
| Type | Schmidt telescope |
| Diameter | 29 cm (11 in) |
| Focal length | 1.4 m (4.6 ft) |
| Wavelengths | visible light |
| Transponders | |
| Band | S Band |
| Bandwidth | 2-23kbit/s |
 Legacy ESA insignia for the Hipparcos mission |
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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. This permitted the accurate determination of proper motions and parallaxes of stars, allowing a determination of their distance and tangential velocity. When combined with radial velocity measurements from spectroscopy, this pinpointed 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.
By the second half of the 20th century, the accurate measurement of star positions from the ground was running into essentially insurmountable barriers to improvements in accuracy, especially for large-angle measurements and systematic terms. Problems were dominated by the effects of the Earth's atmosphere, but were compounded by complex optical terms, thermal and gravitational instrument flexures, and the absence of all-sky visibility. A formal proposal to make these exacting observations from space was first put forward in 1967.
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