# MLS (Microwave Limb Sounder)
*sensor . products*

Passive microwave limb-sounding radiometer/spectrometer aboard Aura for vertical profiles of atmospheric gases, temperature, pressure, and cloud ice, with ozone-chemistry and upper-tropospheric pollution products.

## Specifications
- **product status**: operational
- **deployment context**: orbital
- **manufacturer**: nasa-jpl
- **sensor**: {"instrument_family":"radiometer","measurement_principle":"passive","frequency_bands_ghz":[118,190,240,640,2500],"notes":"MLS looks forward from Aura at the atmospheric limb, scanning from the ground to about 90 km every about 25 seconds. Spatial resolution varies by product; NASA Earthdata lists 200-500 km horizontal and about 3 km vertical resolution."}
- **entity type**: sensor
- **last verified date**: 2026-06-14
- **verified by**: agency-doc
- **claim status**: agency-sourced
- **provider**: nasa-jpl
- **attributes**: {"kind":"sensor","product_status":"operational","deployment_context":"orbital","manufacturer":"nasa-jpl","description":"Passive microwave limb-sounding radiometer/spectrometer aboard Aura for vertical profiles of atmospheric gases, temperature, pressure, and cloud ice, with ozone-chemistry and upper-tropospheric pollution products.","sensor":"{\"instrument_family\":\"radiometer\",\"measurement_principle\":\"passive\",\"frequency_bands_ghz\":[118,190,240,640,2500],\"notes\":\"MLS looks forward from Aura at the atmospheric limb, scanning from the ground to about 90 km every about 25 seconds. Spatial resolution varies by product; NASA Earthdata lists 200-500 km horizontal and about 3 km vertical resolution.\"}"}
- **technology**: microwave-radiometry
- **relevance**: in-scope

## Editorial
MLS is the Microwave Limb Sounder flown on NASA's Aura mission [^nasa-earthdata-mls][^jpl-mls-overview]. It is a passive microwave limb-sounding radiometer and spectrometer that measures thermal emission from the atmospheric limb [^nasa-earthdata-mls][^nasa-mls-factsheet]. Unlike nadir-viewing optical trace-gas instruments, MLS looks forward from Aura at the limb and scans from the ground to about 90 km roughly every 25 seconds [^jpl-mls-overview].

The instrument uses broad microwave and submillimetre bands at 118, 190, 240, and 640 GHz, plus a 2.5 THz channel [^nasa-mls-factsheet]. Its products include vertical profiles of ozone and other trace species, plus temperature, pressure, and cloud ice information for stratospheric ozone, climate, and air-quality science [^jpl-mls-overview][^nasa-earthdata-mls]. Spatial resolution varies by retrieved product, with NASA Earthdata listing about 200 to 500 km horizontal resolution and about 3 km vertical resolution [^nasa-earthdata-mls].

For buyers, MLS is relevant when vertical atmospheric structure matters more than horizontal imaging detail. Its limb-sounding geometry makes it useful for profile retrievals and upper-atmosphere chemistry studies, while its microwave measurement approach provides a different observing regime from ultraviolet-visible nadir spectrometers [^nasa-earthdata-mls][^nasa-mls-factsheet]. JPL developed, built, tested, and operates MLS on Aura [^nasa-mls-factsheet]. Users comparing Aura payloads should treat MLS as a profile-oriented microwave sensor, complementary to nadir atmospheric chemistry instruments that deliver column or near-column products [^jpl-mls-overview][^nasa-earthdata-mls].

## Compositional position
- aura (missions) --[mission_payloads]--> MLS (Microwave Limb Sounder)

## Sources
- [nasa-earthdata-mls] | NASA Earthdata instrument record: MLS | https://www.earthdata.nasa.gov/data/instruments/mls | tier=agency-doc | accessed=2026-06-14
- [jpl-mls-overview] | JPL Aura MLS overview | https://mls.jpl.nasa.gov/eos-aura-mls/ | tier=agency-doc | accessed=2026-06-14
- [nasa-mls-factsheet] | NASA Facts: Microwave Limb Sounder | https://d2pn8kiwq2w21t.cloudfront.net/documents/mls1.pdf | tier=agency-doc | accessed=2026-06-14

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Source: https://eo-atlas.org/products/sensor/mls
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