The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) was a twelve-channel, six-frequency, total power passive-microwave radiometer system. It measured brightness temperatures at 6.925, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz. Vertically and horizontally polarized measurements were taken at all channels. The Earth-emitted microwave radiation was collected by an offset parabolic reflector 1.6 meters in diameter that scanned across the Earth along an imaginary conical surface, maintaining a constant Earth incidence angle of 55° and providing a swath width array of six feedhorns which then carried the radiation to radiometers for measurement. Calibration was accomplished with observations of cosmic background radiation and an on-board warm target. Spatial resolution of the individual measurements varied from 5.4 km at 89.0 GHz to 56 km at 6.9 GHz.