The Advanced Microwave Sounding Unit (AMSU) is an instrument on the Advanced TIROS-N (ATN) NOAA K-N series of operational meteorological satellites. The AMSU consists of two functionally independent units, AMSU-A and AMSU-B. 

AMSU-B is a line-scan instrument designed to measure scene radiance in five channels, ranging from 89 GHz to 183 GHz for the computation of atmospheric water vapor profiles. AMSU-B is a total power system with a FOV of 1.1 degrees at half-power points. The antenna provides a cross-track scan, scanning 50 degrees on either side of the orbital track with 90 IFOVs per scan line. On-board calibration is accomplished with blackbody targets and space as references. AMSU-B channels at the center frequency (GHz) are: 90, 157, and 3 channels at 183.31.