The AVHRR/3 is a six channel imaging radiometer that detects energy in the visible IR portions of the electromagnetic spectrum. It measures reflected solar (visible and near-IR) energy and radiated thermal energy from land, sea, clouds, and the intervening atmosphere.
The HIRS/4 is an atmospheric sounding instrument that provides multispectral data from one visible channel, seven shortwave channels, and twelve longwave channels using a single telescope and a rotating filter wheel containing twenty individual spectral filters.
The AMSU-A is a cross-track scanning total power radiometer, which is divided into two physically separate modules that interface with the spacecraft independently. The AMSU-A measures scene radiance in the microwave spectrum. The data from this instrument is used in conjunction with the HIRS and provides precipitation and surface measurements including snow cover, sea ice concentration, and soil moisture.
The MHS is a new instrument for the NOAA series of satellites. It is a five-channel microwave instrument intended primarily to measure profiles of atmospheric humidity. Additionally, it measures cloud liquid water content and provides qualitative estimates of the precipitation rate.
The SBUV/2 is a nadir-pointing, nonspatial, spectrally scanning, ultraviolet radiometer carried in two modules - the Sensor Module and the Electronics Module. This instrument measures solar irradiance and Earth radiance (backscattered solar energy) in the near ultraviolet spectrum.