A key component of the NPOESS instrument suite is the Advanced Technology Microwave Sounder (ATMS). It is a 22-channel passive microwave spectrometer imaging the earth with spatial resolutions at nadir of ~75 km at 23.8-31.4 GHz (oceanic humidity), ~33 km at 50-89 GHz (temperature profiles; 14 channels), and ~15 km at 165-190 GHz (humidity profiles and precipitation; 6 channels). The swath width is such that every point on earth is imaged at least twice daily per satellite.

In combination with CrIS, a hyperspectral infrared sounder, ATMS will provide temperature and humidity profile information of sufficient accuracy, even in the presence of many cloud types, to improve further the presently respectable accuracy of operational numerical weather prediction models. ATMS should also extend the time series data on mean global upper air temperatures that began with its predecessor instrument, MSU, over twenty years ago. It will also yield global precipitation-rate retrievals for rain and snow with ~15-km resolution near nadir.