# Multi-frequency microwave imaging radiometry
*methodologies*

Retrieves sea surface temperature, sea ice concentration, snow water equivalent, soil moisture, and atmospheric water vapour from natural microwave emission measured across multiple frequencies (roughly 6 to 89 GHz) by a conically scanning imager. The workhorse for global ocean, cryosphere, and hydrological monitoring at a daily cadence.

## Specifications
- **family**: Passive microwave
- **requirements envelope**: {"kind":"spectral","spectral_range_nm":{"min":3000000,"max":30000000},"bands_min":2,"calibration_tier_min":"radiometric","snr_min":10,"daylight_required":false,"cloud_tolerant":true}
- **entity type**: methodology
- **last verified date**: 2026-05-22
- **verified by**: sw
- **claim status**: unclaimed
- **attributes**: {"family":"Passive microwave","summary":"Retrieves sea surface temperature, sea ice concentration, snow water equivalent, soil moisture, and atmospheric water vapour from natural microwave emission measured across multiple frequencies (roughly 6 to 89 GHz) by a conically scanning imager. The workhorse for global ocean, cryosphere, and hydrological monitoring at a daily cadence.","requirements_envelope":"{\"kind\":\"spectral\",\"spectral_range_nm\":{\"min\":3000000,\"max\":30000000},\"bands_min\":2,\"calibration_tier_min\":\"radiometric\",\"snr_min\":10,\"daylight_required\":false,\"cloud_tolerant\":true}"}
- **technology**: microwave-radiometry

## Editorial
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](https://en.wikipedia.org/wiki/Passive_microwave_remote_sensing)

## Sources
- [wikipedia] | Wikipedia: Passive microwave remote sensing | https://en.wikipedia.org/wiki/Passive_microwave_remote_sensing | tier=community | accessed=2026-05-22

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Source: https://eo-atlas.org/methodologies/passive-microwave-radiometry
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