Abstract
Abstract. The FY3 (Feng-Yun-3) GNOS (GNSS Occultation Sounder) mission is a GNSS (Global Navigation Satellite System) radio occultation mission of China for remote sensing of Earth's neutral atmosphere and the ionosphere. GNOS will use both the global positioning system (GPS) and the Beidou navigation satellite systems on the China Feng-Yun-3 (FY3) series satellites. The first FY3-C was launched at 03:07 UTC on 23 September 2013. GNOS was developed by the Center for Space Science and Applied Research, Chinese Academy of Sciences (CSSAR). It will provide vertical profiles of atmospheric temperature, pressure, and humidity, as well as ionospheric electron density profiles on a global basis. These data will be used for numerical weather prediction, climate research, and ionospheric research and space weather. This paper describes the FY3 GNOS mission and the GNOS instrument characteristics. It presents simulation results of the number and distribution of GNOS occultation events with the regional Beidou constellation and the full GPS constellation, under the limitation of the GNOS instrument occultation channel number. This paper presents the instrument performance as derived from analysis of measurement data in laboratory and mountain-based occultation validation experiments at Mt. Wuling in Hebei Province. The mountain-based GNSS occultation validation tests show that GNOS can acquire or track low-elevation radio signal for rising or setting occultation events. The refractivity profiles of GNOS obtained during the mountain-based experiment were compared with those from radiosondes. The results show that the refractivity profiles obtained by GNOS are consistent with those from the radiosonde. The rms of the differences between the GNOS and radiosonde refractivities is less than 3%.
Highlights
When a receiver on board a low Earth orbiting (LEO) spacecraft tracks a Global Navigation Satellite System (GNSS) satellite in higher orbits as it sets or rises through Earth’s atmosphere, a radio occultation (RO) occurs
The first demonstration of RO for Earth’s atmosphere was the global positioning system (GPS)/MET experiment led by the University Corporation for Atmospheric Research (UCAR), which was equipped with the NASA/JPL Turbo-Rogue GPS receiver modified to acquire and track occultation signals (Ware et al, 1996)
This paper provides a basic introduction to the GNOS RAOA and SAOA) have a pattern that is wide in azimuth and instrument
Summary
When a receiver on board a low Earth orbiting (LEO) spacecraft tracks a Global Navigation Satellite System (GNSS) satellite in higher orbits as it sets or rises through Earth’s atmosphere, a radio occultation (RO) occurs. The GNOS mission (Bi et al, 2012) consists of a GNSS pable of tracking up to six Beidou satellites and more than radio occultation explorer for remote sensing of both the eight GPS satellites through this antenna. With the limitation of the GNOS instrument occultation channel number described in Table 1 and the occultation antenna coverage range in azimuth (+35 to −35◦), a total of 696 occultation events, including 192 (98 risings + 94 settings) Beidou occultation events and 534 (268 risings + 266 settings) GPS occultation events, can be obtained. The global distribution for all simulated occultation events for Beidou and GPS is shown in Figs. 2 and 3 respectively
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