GALEX (Galaxy Evolution Explorer) is an American (NASA) astronomy spacecraft that was launched at 12:00 UT on 2003 April 28 by a Pegasus XL rocket released from a L-1011 cargo plane flying out of Cape Canaveral. It is a 280-kg, 290-W, triaxially-stabilized satellite, and carried a UV telescope. The initial orbital parameters were period 98.6 min, apogee 697 km, perigee 691 km, and inclination 29.0 degrees.
The Galaxy Evolution Explorer (GALEX) is an orbiting space ultraviolet telescope, which explores the origin and evolution of galaxies, and the origins of stars and heavy elements over the redshift range of z between 0 and 2. GALEX conducted an all-sky imaging survey, a deep imaging survey, and a survey of 200 galaxies nearest to the Milky Way Galaxy. GALEX also performed three spectroscopic surveys over the 135-300 nanometer band. GALEX had a planned 29 month mission, and is a part of the Small Explorers (SMEX) program.
The spacecraft ia three-axis stabilized, with power coming from four fixed solar panels. The spacecraft bus is from Orbital Sciences Corporation based on OrbView 4. The telescope is a 50-cm Modified Ritchey-Chretien with a rotating grism. GALEX uses the first ever UV light dichroic beam-splitter flown in space to direct photons to the Near UV (175-280 nanometers) and Far UV (135-174 nanometers) microchannel plate detectors. Each of the two detectors has a 65 millimeter diameter. The target orbit is 670 km circular and inclined at 28.5 degrees to the equator.
UV Telescope: GALEX carries a single f/6.0, Richey-Chretien UV telescope, with a 50-cm diameter primary, and a 22-cm secondary mirror. Beam-splitters direct the Near UV (NUV) and Far UV (FUV) components to separate photoelectric detectors of diameter 6.5 cm. In each, the photoelectrons are multiplied by a microchannel plate and detected by the anode grid. The grid enables determination of the exact position of electron impact, by the time delay of each pulse at the two ends. The telescope has a field of view of 1.2 degrees and a resolution of 5 arc-seconds, and enables either imaging or spectral composition of a single star/galaxy by a rotatable wheel containing a clear window and a Grism. (A Grism is a cross between a grating and a prism.)
Alternate Names
Explorer 83
Galaxy Evolution Explorer
SMEX/GALEX
Small Explorer/GALEX
Facts in Brief
Launch Date: 2003-04-28
Launch Vehicle: Pegasus XL
Launch Site: Cape Canaveral, United States
Mass: 280.0 kg
Nominal Power: 290.0 W