GPS RADIO OCCULTATION (Tangent point)

GNSS or GPS radio occultation

(New and future observing systems)

"The radio occultation (RO) technique, which makes use of radio signals transmitted by the global positioning system (GPS) satellites, has emerged as a powerful and relatively inexpensive approach for sounding the global atmosphere with high precision, accuracy, and vertical resolution in all weather and over both land and ocean. On 15 April 2006, the joint Taiwan - U.S. Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC)/Formosa Satellite Mission 3 (COSMIC/FORMOSAT-3, hereafter COSMIC) mission, a constellation of six microsatellites, was launched into a 512-km orbit. After launch the satellites were gradually deployed to their final orbits at 800 km, a process that took about 17 months. During the early weeks of the deployment, the satellites were spaced closely, offering a unique opportunity to verify the high precision of RO measurements. As of March 2013, COSMIC is still providing about 1500 RO soundings per day to support the research and operational communities. COSMIC RO data are of better quality than those from the previous missions and penetrate much closer to the Earth's surface; 70% - 90% of the soundings reach to within 1 km of the surface on a global basis. The data are having a positive impact on operational global weather forecast models.

Ref. :

http://www.cosmic.ucar.edu/ro.html

https://en.wikipedia.org/wiki/GNSS_radio_occultation

https://en.wikipedia.org/wiki/Radio_occultation