  The Wide-field Infrared Survey Explorer (WISE), a NASA MIDEX mission, will
survey the entire sky in four bands from 3.3 to 23 microns with a sensitivity
1000 times greater than the IRAS survey. The WISE survey will extend the Two
Micron All Sky Survey into the thermal infrared and will provide an important
catalog for the James Webb Space Telescope. Using 1024x1024 HgCdTe and Si:As
arrays at 3.3, 4.7, 12 and 23 microns, WISE will find the most luminous
galaxies in the universe, the closest stars to the Sun, and it will detect most
of the main belt asteroids larger than 3 km. The single WISE instrument
consists of a 40 cm diamond-turned aluminum afocal telescope, a two-stage solid
hydrogen cryostat, a scan mirror mechanism, and reimaging optics giving 5"
resolution (full-width-half-maximum). The use of dichroics and beamsplitters
allows four color images of a 47'x47' field of view to be taken every 8.8
seconds, synchronized with the orbital motion to provide total sky coverage
with overlap between revolutions. WISE will be placed into a Sun-synchronous
polar orbit on a Delta 7320-10 launch vehicle. The WISE survey approach is
simple and efficient. The three-axis-stabilized spacecraft rotates at a
constant rate while the scan mirror freezes the telescope line of sight during
each exposure. WISE is currently in its Preliminary Design Phase, with the
mission Preliminary Design Review scheduled for July, 2005. WISE is scheduled
to launch in mid 2009; the project web site can be found at
www.wise.ssl.berkeley.edu.
