Multi-frequency microwave imaging radiometry

A conically scanning radiometer measures brightness temperature at several frequencies between roughly 6 and 89 GHz, each in dual polarisation, and inverts the multi-frequency signal against emission models to separate surface and atmospheric contributions. The breadth of the frequency set is what distinguishes this imaging approach from single-band L-band radiometry: the higher channels resolve sea surface temperature, sea ice, snow water equivalent, and water vapour that a 1.4 GHz instrument cannot. Coarse spatial resolution (tens of km, strongly frequency-dependent) limits applicability over heterogeneous terrain. The method is cloud-independent and operates day and night. Wikipedia: Passive microwave remote sensing