Application of Fengyun 3-C GNSS occulation sounder for assessing global ionospheric response to magnetic storm event

Abstract

Abstract.14 The rapid advancement of global navigation satellite system (GNSS) occultation technology in recent years has 15 made it one of the most advanced space detection technologies of the 21st century. GNSS radio occultation has 16 many advantages, including all-weather operation, global coverage, high vertical resolution, high precision, 17 long-term stability, and self-calibration. Data products from GNSS occultation sounding can greatly enhance 18 ionospheric observations and contribute to space weather monitoring, forecasting, modeling, and research. In this 19 study, GNSS occultation sounder (GNOS) results from a radio occultation sounding payload aboard the Fengyun 20 3-C (FY3-C) satellite were compared with ground-based ionosonde observations. Correlation coefficients for 21 peak electron density (NmF2) derived from GNOS Global Position System (GPS) and Beidou navigation system 22 (BDS) products with ionosonde data were higher than 0.9, and standard deviations were less than 20 %. Global 23 ionospheric effects of the strong magnetic storm event in March 2015 were analyzed using GNOS results 24supported by ionosonde observations. The magnetic storm caused a significant disturbance in NmF2 and hmF2 25 levels. Suppressed daytime and nighttime NmF2 levels indicated mainly negative storm conditions. In the zone 26 of geomagnetic inclination between 40-80°, average NmF2 during the geomagnetic storm showed the same 27 basic trends in GNOS measurements, and in observations from 17 ground-based ionosonde stations, and 28 confirmed the negative effect of the event on the ionosphere. The analysis demonstrates the reliability of the 29 GNSS radio occultation sounding instrument GNOS aboard the FY3-C satellite, and confirms the utility of 30 ionosphere products from GNOS for statistical and event-specific ionospheric physical analyses. Future FY3

The FengYun-3C radio occultation sounder GNOS: a review of the mission and its early results and science applications

“…Under the condition of fewer reference satellites, a zero-difference technique is applied and more appropriate for BDS RO events, since it does not require a reference satellite for simultaneous observations but requires an ultra-stable oscillator on an LEO receiver (Beyerle et al, 2005), which is available for GNOS (cf. Table 1; Bai et al, 2018). Based on the encouraging results of Bai et al (2018), an in-depth comparison of the zero-differencing and single-differencing FY-3C GNOS RO data products has been started to evaluate whether the zero-differencing method can be used instead of the single-difference method in the operational data processing.…”

“…The development of GNSSs such as China's BeiDou Navigation Satellite System (BDS), Russia's GLObal NAvigation Satellite System (GLONASS), and the European Galileo system has significantly enhanced the availability and capacity of the GPS-like satellites, which will make GNSS RO even more attractive in the future (Bai et al, 2018). These new GNSS satellites, together with planned low Earth orbit (LEO) missions, will offer many more RO observations in the future (Wang et al, 2015;Cai et al, 2017).…”

“…These new GNSS satellites, together with planned low Earth orbit (LEO) missions, will offer many more RO observations in the future (Wang et al, 2015;Cai et al, 2017). One of these LEO missions is China's GNSS Occultation Sounder (GNOS) on board the FengYun 3 series C (FY-3C) satellite, which was successfully launched on 23 September 2013 (Wang et al, 2013(Wang et al, , 2014Bai et al, 2014bBai et al, , 2016Liao et al, 2015Liao et al, , 2016aWang et al, 2016;Du et al, 2016).…”

“…The FY-3C GNOS mission was designed and developed by the National Space Science Center, Chinese Academy of Sciences (NSSC/CAS), to sound the Earth's neutral atmosphere and ionosphere by using both the BDS and GPS sig- nals (Wang et al, 2015;Bai et al, 2018). The FY-3C satellite is the first BDS-and GPS-compatible RO sounder with a state-of-the-art RO receiver -GNOS (Bai et al, 2012(Bai et al, , 2014aWang et al, 2015;Du et al, 2016).…”

“…An ultra-stable oscillator (USO) is used as a reference oscillator with highly stable frequency (1 s Allan deviation of 10 −12 ), in order to retrieve atmospheric measurements with high accuracy (Du et al, 2016;Sun et al, 2017). It also allows data users to invert the excess phase by using the zero-difference method (Beyerle et al, 2005;Bai et al, 2018).…”