MAP (Microwave Anisotrophy Probe) is a follow up mission to COBE, which detected the anisotophy of the microwave
background radiation. It has one instrument, which consists of a set of passively cooled
microwave radiometers with 1.4 × 1.6 meter diameter primary gregorian reflectors to
provide the desired angular resolution. The instrument has five frequency bands from
22 to 90 GHz to facilitate separation of galactic foreground signals from the cosmic
background radiation.
MAP uses differential measuring, i.e.it measures the temperature difference between two
points in the sky rather than measuring absolute temperatures. An orbit about the
Sun-Earth L2 libration point provides for a very stable thermal environment and near 100
percent observing efficiency since the Sun, Earth, and Moon are always behind the
instruments field of view.
It was launched in a highly excentric phasing orbit, at the fourth apogee it made a
lunar fly-by and moved to a L-2 Sun-Earth Lagrangian orbit.
MAP was re-christened Wilkinson Microwave Anisotropy Probe (WMAP)
in February 2003.
In October 2010, the WMAP spacecraft was derelict in a heliocentric graveyard orbit after completing 9 years of operations.
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