Imaging multi-spectral radiometers - passive microwave

"Operating at microwave wavelengths, imaging multi-spectral radiometers have the advantage of cloud penetration and all-weather capability. Channels within 1 GHz to 40 GHz and 80 GHz to 100 GHz are used to get day/night information on Earth’s surface. They have the advantage over visible/IR radiometers of being able to probe the dielectric properties of a surface or penetrate certain surfaces, a capability that is especially useful with vegetation, soil, sea ice and snow. Observations by instruments like AMSU-A, with channels between 50 GHz and 60 GHz, have been used for deriving atmospheric parameters, especially atmospheric temperature.

Like other microwave instruments, these passive instruments offer accurate spectral information but their spatial resolution is poor. At 90 GHz, their spatial resolution is typically 5 km, and for the lower frequencies it is of order tens of kilometres – poorer than that of their visible or infrared counterparts. As a consequence, they are most used for global analysis rather than regional or local, although some instruments are used to correct measurements from other sensors, rather than for imaging applications." (ESA 2015)
 

Sources

European Space Agency (ESA) 2015. “The Earth Observation Handbook: Special Edition for Rio+20.”