page_title: Radio occultation
section_title: GNSS radio occultation
hierarchical_section_title: Radio occultation / GNSS radio occultation
caption_attribution_description: English: The diagram illustrates radio occultation and refraction.
context_page_description: Radio occultation is a remote sensing technique used for measuring the physical properties of a planetary atmosphere or ring system.
context_section_description: GNSS radio occultation (GNSS-RO), historically also known as GPS radio occultation (GPS-RO or GPSRO), is a type of radio occultation that relies on radio transmissions from GPS (Global Positioning System), or more generally from GNSS (Global Navigation Satellite System), satellites. This is a relatively new technique (first applied in 1995) for performing atmospheric measurements. It is used as a weather forecasting tool, and could also be harnessed in monitoring climate change. The technique involves a low-Earth orbit satellite receiving a signal from a GPS satellite. The signal has to pass through the atmosphere and gets refracted along the way. The magnitude of the refraction depends on the temperature and water vapor concentration in the atmosphere.
  GPS Radio occultation amounts to an almost instantaneous depiction of the atmospheric state. The relative position between the GPS satellite and the low-Earth orbit satellite changes over time, allowing for a vertical scanning of successive layers of the atmosphere.
  GPSRO observations can also be conducted from aircraft. or on high mountaintops.
caption: Illustration of radio occultation
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