The galaxy evolution explorer

The Galaxy Evolution Explorer (GALEX), a NASA Small Explorer Mission planned for launch in Fall 2002, will perform the first Space Ultraviolet sky survey. Five imaging surveys in each of two bands (1350-1750 Å and 1750-2800Å) will range from an all-sky survey (limit m_AB∼20-21) to an ultra-deep survey of 4 square degrees (limit m_AB∼26). Three spectroscopic grism surveys (R=100-300) will be performed with various depths (m_AB∼20-25) and sky coverage (100 to 2 square degrees) over the 1350-2800 Å band. The instrument includes a 50 modified Ritchey-Chrétien telescope, a dichroic beam splitter and astigmatism corrector, two large sealed tube microchannel plate detectors to simultaneously cover the two bands and the 1.2 degree field of view. A rotating wheel provides either imaging or grism spectroscopy with transmitting optics. We will use the measured UV properties of local galaxies, along with corollary observations, to calibrate the UV-global star formation rate relationship in galaxies. We will apply this calibration to distant galaxies discovered in the deep imaging and spectroscopic surveys to map the history of star formation in the universe over the red shift range zero to two. The GALEX mission will include an Associate Investigator program for additional observations and supporting data analysis. This will support a wide variety of investigations made possible by the first UV sky survey.