The Complete Book of Spaceflight: From Apollo 1 to Zero Gravity

146 GAIA (Global Astrometric Interferometer for Astrophysics)
GAIA (Global Astrometric Interferometer for
Astrophysics)
A proposal for an advanced space astrometry (stardistance
measurement) mission to build on the work
started by Hipparcos. It has been recommended within
the context of ESA’s (European Space Agency’s) Horizon
2000 Plus plan for long-term space science. GAIA
would measure the distance and velocity of more than a
billion stars in the galaxy to an accuracy 100 to 1,000
times higher than that possible with Hipparcos. It would
also carry out a special study of some 200,000 stars within
650 light-years of the Sun in a search for Jupiter-mass
planets. GAIA is expected to be launched around
2010–2012 and to operate for five years.
Galaxy
A constellation of about 10 geostationary communications
satellites owned and operated by PanAmSat. The
latest members of the constellation are Galaxy 3C,
launched on June 2, 2002, by a Zenit 35L from the Sea
Launch platform; and Galaxy 13, which was scheduled
for launch in the last quarter of 2002.
GALEX (Galaxy Evolution Explorer)
A SMEX (Small Explorer) mission designed to make
ultraviolet observations that will shed light on the origin
and evolution of galaxies. GALEX is equipped with a 50cm
telescope sensitive in the region of 130 to 300 nm and
an efficient spectroscope that can obtain the spectra of
about 100,000 galaxies per year. Partners in the project
include NASA, JPL (Jet Propulsion Laboratory), the
Orbital Science Corporation, and various universities in
California, France, and Japan. GALEX will probably be
launched in 2003.
Galileo
See article, pages 147–148.
Galileo satellite navigation system
A planned European satellite navigation system, similar
to GPS (the U.S. military’s Global Positioning System)
but run on a purely civilian basis. It is being developed
by ESA (European Space Agency) in collaboration with
the European Union (the first such joint project) and is
expected to be operational by 2008. Its goal is to provide
the world in general and Europeans in particular with an
accurate, secure, and certified satellite positioning system
with applications in road, rail, air, and maritime traffic
control, synchronization of data transmission between
banks, and so forth. Although Galileo will be in commercial
competition with GPS (and so, not surprisingly,
has been opposed by the U.S. government), it will also
complement GPS and provide redundancy. The Galileo
GALEX An artist’s conception of GALEX in orbit. NASA/JPL
system will consist of 30 satellites (27 in operation and 3
in reserve), deployed in three circular medium Earth
orbits at an altitude of 23,616 km and an inclination of
56° to the equator. Two control centers will be set up in
Europe to monitor the operation of the satellites and
manage the navigation system. A precursor of the system
is EGNOS (European Global Navigation Overlay Service),
which refines current GPS data and foreshadows
the services Galileo will provide.
Gamma
An orbiting Soviet gamma-ray and X-ray telescope
derived from Soyuz-manned spacecraft hardware. It was
originally conceived in 1965 as part of a “Cloud Space
Station”—a primary space station from which a number
of man-tended, free-flying spacecraft would operate. This
had evolved by the early 1970s into the MKBS/MOK
space station complex. Various spacecraft with specialized
laboratories or instrument sets, including Gamma,
would fly autonomously away from the N-1–launched
main station. The Soyuz propulsion system would be
used, but the descent and orbital modules were replaced
by a large pressurized cylinder containing the scientific
instruments. Work on the instrument payload for
Gamma began in 1972, and French participation began
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