Advanced Microwave Scanning Radiometer for EOS (AMSR-E)

The Advanced Microwave Scanning Radiometer for EOS (AMSR-E) was a twelve-channel, six-frequency conical-scan passive-microwave imaging radiometer developed and provided by JAXA, built by Mitsubishi Electric Corporation, and flown aboard the NASA Aqua satellite, which launched on 4 May 2002.^[1][2] AMSR-E was the first JAXA-provided instrument aboard a NASA Earth Observing System (EOS) spacecraft.

The instrument used an offset parabolic reflector 1.6 m in diameter, rotating at 40 rpm in a conical scan geometry at a fixed Earth incidence angle of 55 degrees, producing a swath width of 1450 km. This geometry provided near-daily global coverage over the instrument's operational life.^[1][3]

AMSR-E operated at six frequency bands: 6.925, 10.65, 18.7, 23.8, 36.5, and 89.0 GHz, with both vertical and horizontal polarisation at each channel, totalling twelve measurement channels.^[1] Spatial footprint at 6.925 GHz was reported as 43 x 75 km by JAXA EORC^[1] and as 74 x 43 km by NASA Earthdata^[3], reflecting a difference in axis convention (along-track x cross-track versus cross-track x along-track) between the two sources; the physical footprint dimensions are equivalent. At 89.0 GHz the instrument carried two feedhorns, achieving footprints of approximately 3.7 x 6.5 km and 3.5 x 5.9 km.^[1]

AMSR-E retrieved a suite of geophysical variables including sea surface temperature, sea ice concentration and extent, snow water equivalent, soil moisture, atmospheric water vapour, precipitation rate, and ocean wind speed.^[3][2] These retrievals supported climate and weather applications including sea ice mapping and global water cycle monitoring.

Designed for a three-year operational life, AMSR-E operated for more than nine years before experiencing a rotation anomaly in which increased rotation friction caused torque to exceed the design limit.^[4] JAXA halted instrument rotation on 4 October 2011 to prevent further mechanical damage.^[4] No further scanning observations were collected after that date.