NASA's Advanced Microwave Scanning Radiometer (AMSR) flew aboard the Advanced Earth Observing Satellite-II (ADEOS-II), operated by the Japan Aerospace Exploration Agency (JAXA). Improving upon the capabilities of earlier passive microwave radiometers, such as the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I), AMSR could collect observations in daylight and nighttime conditions, and in any kind of weather with minimal interference from clouds. These remote sensing capabilities are crucial to observing polar regions year-round, including months-long stretches of polar darkness.

The ADEOS-II satellite launched on December 14, 2002. The mission was planned to operate for three to five years, but problems with the satellite's electrical supply ended operations on October 25, 2003.

Data obtained by AMSR support efforts to understand Earth's water and energy cycle. The AMSR series of platforms (which includes AMSR2 and AMSR-E) provide a continual data record of polar observations, uninterrupted by clouds or months of polar darkness.