GNSS radio occultation

GNSS or GPS radio occultation (GNSS-RO, GPS-RO, 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.

Introduction

GPS radio occultation 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.

File:RO schematic.jpg

Illustration of radio occultation

Satellite missions

• FORMOSAT-3/COSMIC
• CHAMP
• GRACE
• GRAS sensor onboard MetOp satellite
• CLARREO

See also

• GPS meteorology

References

• Melbourne et al. 1994. The application of spacebourne GPS to atmospheric limb sounding and global change monitoring. Publication 94-18, Jet Propulsion Laboratory
• Kursinski et al. 1997. Observing the Earth's atmosphere with radio occultation measurements using the Global Positioning System. J. Geophys. Res. 102:23.429-23.465.

External links

• COSMIC Project Website
• GeoOptics LLC Website - First commercial operational RO Constellation
• PlanetIQ Website
• ROM SAF monitoring
• ROM SAF website
• ECMWF monitoring