This section deals with microwave remote sensing which aims at extracting information on physical structure and electrical properties of an object or a scene by electromagnetical field analysis (sea, ice, ground, vegetation, urban areas, atmosphere, rain and clouds …).

Microwave remote sensing uses passive microwave radiometers. The microwaves have wavelength ranging from a few kHz to THz. The "passive" term means that it uses microwaves naturally radiated by the observed area (this is different from the radar principle where the sensor transmits a microwave signal towards a target and detects the backscattered radiation).
Microwave radiometer brightness temperatures are considered as a fundamental climate data record and are the values from which we derive ocean measurements of wind speed, water vapor, cloud liquid water, rain rate, and sea surface temperature.
The main passive microwave radiometers are presented and the link between radiometers and altimeters is detailed.