The MAP instrument consists of a set of passively cooled microwave radiometers with 1.4 x 1.6 meter diameter primary reflectors to provide the desired angular resolution. The sensitivity of the cosmic microwave background map will be better than 20 microKelvin (0.000020 Kelvin) per 0.3 degree square pixel. MAP will measure temperature differences on the sky using symmetric microwave receivers coupled to back-to-back telescopes. By measuring temperature differences, rather than absolute temperatures, most spurious signals will cancel. Five frequency bands from 22 GHz to 90 GHz will allow emission from the Galaxy and environmental disturbances to be modeled and removed based on their frequency dependence. The MAP instrument will be continuously shaded from the Sun, Earth, and Moon by the spacecraft. 

MAP will observe from a Lissajous orbit about the L2 Sun-Earth Lagrange point 1.5 million km from Earth. The trajectory selected to attain such an orbit consists of 2.5-3.5 lunar phasings loops followed by a ~100 day cruise to L2. No thruster firings are required to enter the L2 orbit. 

The following animation indicates the path MAP will follow to L2. The trajectory features 2.5 or 3.5 lunar phasing loops which assist the spacecraft in reaching L2. The cruise time to L2 is approximately 100 days after the lunar phasing loops are completed. Once in orbit about L2, the satellite maintains a Lissajous orbit such that the MAP-Earth vector remains between 1 and 10 degrees off the Sun-Earth vector to satisfy communications requirements while avoiding eclipses. Station-keeping maneuvers will be required ~4 times per year to maintain this orbit.

Courtesy NASA GSFC: MAP Trajectory to L2

MAP will rotate once every two minutes around its spin axis, with the aid of three "reaction wheels" symmetrically placed around the base of the spacecraft. The spin axis of MAP will maintain a fixed angle of 22.5 degrees with respect to the Sun-Earth line. This axis will revolve around the Sun-Earth line every hour, and rotate annually with the Earth around the Sun. This scan pattern will permit MAP to see any one point in the sky from many different perspectives.

The NASA Goddard Space Flight Center, Princeton University, UCLA, and The University of Chicago are the Science Team institutions that are responsible for the MAP Project.