Infobox Space telescope
name = Hipparcos
caption = Artist's conception of Hipparcos in space
European Space Agency
Geostationary transfer orbit
height = 507 to 35,888 km
8 August 1989
mission_length = 3.5 years
diameter = 29 cm
focal_length = 1.4 m
acronymfor "High Precision Parallax Collecting Satellite") was an astrometrymission of the European Space Agency(ESA) dedicated to the measurement of stellar parallax and the proper motions of stars. The project was named in honor of Hipparchus. Ideas for such a mission dated from 1967, with the mission accepted by ESA in 1980.
The Hipparcos satellite was a product of
Matra Marconi Space, Alenia Spazioand their industrial partners. The optical system had a 290 mm aperture, 1400 mm focal lengthfolded Schmidt telescope. The expected precision of the instrument was in the range of 0.001–0.002 arcsecond. The satellite also included solar panels for power and an s-bandantenna for communication. [cite conference
first = A. | last = Peraldi
title =The Hipparcos payload optics
booktitle =Technology for Space Astrophysics Conference: The Next 30 Years
publisher =American Institute of Aeronautics and Astronautics
date =October 4-6, 1982 | location =Danbury, CT
accessdate = 2007-06-12 ]
The satellite was launched by an
Ariane 4on 8 August 1989. The launch mass of Hipparcos was 500 kg. [cite web
author=Staff | date=June 12, 2007
title=Hipparcos | publisher=ESA
accessdate=2007-06-12 ] The original goal was to place the satellite in a
geostationary orbitabove the earth, but failure of the apogeeboost motor resulted in a highly elliptical geostationary transfer orbitwith an altitudevarying between 507 and 35,888 km . Despite this difficulty, all of the scientific goals were accomplished. Communications were terminated on 15 August 1993.
The program was divided in two parts: the "Hipparcos experiment" whose goal was to measure the five astrometric parameters of some 120,000 stars to a precision of some 2 to 4 milli
arcseconds and the "Tycho experiment", whose goal was the measurement of the astrometric and two-colour photometric properties of some 400,000 additional stars to a somewhat lower precision.
Due to the built-in beam-splitter, Hipparcos continuously scanned the sky in two directions, separated by 58°. The image was split into a grid by 3,000 parallel slits, allowing the separation of the stars in the field of view to be measured to a high degree of accuracy. [cite web
last=Turon | first=Catherine | year=1997
title=From Hipparchus to Hipparcos: Measuring the Universe, One Star at a Time
publisher=Sky Publishing Corporation
Hipparcos Catalogue(120,000 stars with 1 milliarcsec level astrometry) and the final Tycho Catalogue (more than one million stars with 20-30 milliarcsec astrometry and two-colour photometry) were completed in August 1996. The catalogues were published by ESA in June 1997.
The Hipparcos and Tycho data have been used to create the
Millennium Star Atlas: an all-sky atlas of one million stars to visual magnitude11, from the Hipparcos and Tycho Catalogues and 10,000 nonstellar objects included to complement the catalogue data.
There were questions over whether Hipparcos has a systematic error of about 1 milliarcsec in at least some parts of the sky. The value determined by Hipparcos for the distance to the Pleiades is about 10% less than the value obtained by some other methods. As of
2007, the controversy remained unresolved. [cite web
last=den Hond | first=Bas | date=September 30, 2004
title =Did the Pleiades "blind" Hipparcos?
publisher =Astronomy Magazine
accessdate = 2007-06-12 ] [cite journal
author=Soderblom, D. R.; Nelan, E.; Benedict, G. F.; McArthur, B.; Ramirez, I.; Spiesman, W.; Jones, B. F
title=Confirmation of Errors in Hipparcos Parallaxes from Hubble Space Telescope Fine Guidance Sensor Astrometry of the Pleiades
journal=The Astronomical Journal | year=2005
volume=129 | pages=1616–1624
Full-Sky Astrometric Mapping Explorer
* [http://www.rssd.esa.int/Hipparcos/hipparcos.html The Hipparcos Space Astrometry Mission]
* [http://cdsweb.u-strasbg.fr/viz-bin/Cat?I/239 The Hipparcos and Tycho Catalogues]
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