The Hipparcos
satellite was launched
by the European Space Agency (
ESA)
in August 1989. After some initial
problems with a
boost motor,
the satellite began its
mission November that year.
The objective of the Hipparcos mission
was the production of a star catalog of
unprecedented accuracy. Based on a
predetermined set of 120,000 stars
of magnitudes down to 13, the satellite
gathered detailed information about
astrometric position,
parallaxes (down to one milli-arc-second),
as well as proper motion data
(down to two milli-arc-seconds).
The measurements was produced by an
Image Dissector Tube (IDT), which sampled
the modulated signal produced by a
star crossing the fine grid slits
located in the focal plane of the
payload telescope.