GNOS-II on Fengyun-3 Satellite Series: Exploration of Multi-GNSS Reflection Signals for Operational Applications
Abstract
:1. Introduction
- The instrument combines GNSS RO and GNSS-R techniques.
- It is capable of receiving reflected signals from multiple GNSS systems including GPS, BeiDou (BDS) and Galileo (GAL), which can improve the spatial sampling for the Earth remote sensing.
- The satellite is in a polar orbit, providing measurements over high latitudes including polar regions.
- The average data latency is less than three hours, providing potential for real-time and near real-time operational applications such as assimilation in operational NWP models and monitoring of tropical cyclones.
- The instrument is working together with a scatterometer, WindRad [22], providing opportunities for intercalibration and data fusion.
2. Overview of the GNOS-II Instrument and the FY-3E Mission
3. Calibration and Intercalibration of Multi-GNSS Reflectometry Data
3.1. Calibration for Each GNSS System over Ocean and Land
3.2. Intercalibration
4. Development of Science Product and Applications
4.1. Ocean Surface Winds
- Global wind product
- Mainly focus on wind speeds over the globe where the sea state of most areas is fully developed.
- The geophysical model function (GMF) was trained by the ECMWF ERA5 reanalysis.
- With best accuracy under 25 m/s.
- Mainly used for global numerical weather prediction (NWP) assimilation, climatology and related studies.
- Cyclone wind product
- Mainly focus on wind speeds over tropical and extratropical cyclones where the sea state is usually under limited fetch.
- The GMF was trained by the Hurricane Weather Research and Forecasting (HWRF) model data.
- With better accuracy at high wind speeds above 25 m/s than global wind product.
- Mainly used for regional NWP assimilation, monitoring of tropical cyclones and related studies.
4.1.1. Global Winds
4.1.2. Cyclone Winds
4.2. Land Soil Moisture
4.3. Sea Ice Extent
5. Cooperation between GNSS-R and GNSS RO
6. Conclusions and Future Perspective
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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FY-3E/GNOS-II | CYGNSS | |
---|---|---|
Altitude | 836 km | 520 km |
Inclination angle | 98.5 | 35 |
Number of nadir reflection antenna | 1 | 2 |
Number of reflection channels | 8 | 4 |
GNSS frequency | GPS L1 C/A, BDS B1I and GAL E1B | GPS L1 C/A |
Coherent integration time | 1 ms | 1 ms |
Non-coherent integration time | 1000 ms | 500/1000 ms |
DDM dimension | 122 delays × 20 Dopplers | 17 delays × 11 Dopplers |
DDM delay resolution | Non-uniform with 0.125 and 0.25 chip [12] | 0.25 chip |
DDM Doppler resolution | 500 Hz | 500 Hz |
Average data latency | <3 h | ∼2 days |
Product | Description |
---|---|
L1 product | Delay-doppler maps (DDMs) geometry parameters, observables, antenna gain and SNR |
L2 wind product | Ocean surface winds, mean square slope, smoothed observables and spatial resolution |
L2 soil moisture product | Land reflectivity, soil moisture, spatial resolution and ancillary data |
Raw IF product | Raw IF sampling data, GNSS PRN code, and collection time |
GNSS Signal | GPS L1C/A | BDS B1I | GAL E1B |
---|---|---|---|
Carrier frequency (MHz) | 1575.42 | 1561.098 | 1575.42 |
Modulation | BPSK | BPSK | BOC(1,1) |
Chipping rate (Mcps) | 1.023 | 2.046 | 2.046 |
Code period (ms) | 1 | 1 | 4 |
GPS | II-R, IIR-M, II-F and III-A |
BDS | BDS-2 IGSO, BDS-2 MEO, BDS-3 IGSO and BDS-3 MEO |
GAL | In-orbit validation (IOV) and Full operational Capability (FOC) |
Calibration Factor | Calibration Method |
---|---|
Instrument gain (G) | Prelaunch thermal cycling experiment |
Antenna pattern () | Prelaunch measurements |
Transmitter EIRP () | Static power monitors |
Effective scattering area () | Empirical lookup-table |
System | GPS | BDS | GAL |
---|---|---|---|
RMSE (cm/cm) | 0.0500 | 0.04999 | 0.0482 |
Correlation coefficient | 0.83 | 0.85 | 0.86 |
System | Detection Rate (%) | False Alarm Rate (%) |
---|---|---|
GPS | 98.78 | 3.65 |
BDS | 99.13 | 2.65 |
GAL | 98.63 | 2.52 |
FY-3E | FY-3F | FY-3G | |
---|---|---|---|
Launch date | 5 July 2021 | 3 August 2023 | 16 April 2023 |
Altitude (km) | 836 | 836 | 407 |
Inclination angle (°) | 98.5 | 98.5 | 50 |
Descending Time | 5:40 | 10:00 | Drifting |
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Sun, Y.; Huang, F.; Xia, J.; Yin, C.; Bai, W.; Du, Q.; Wang, X.; Cai, Y.; Li, W.; Yang, G.; et al. GNOS-II on Fengyun-3 Satellite Series: Exploration of Multi-GNSS Reflection Signals for Operational Applications. Remote Sens. 2023, 15, 5756. https://doi.org/10.3390/rs15245756
Sun Y, Huang F, Xia J, Yin C, Bai W, Du Q, Wang X, Cai Y, Li W, Yang G, et al. GNOS-II on Fengyun-3 Satellite Series: Exploration of Multi-GNSS Reflection Signals for Operational Applications. Remote Sensing. 2023; 15(24):5756. https://doi.org/10.3390/rs15245756
Chicago/Turabian StyleSun, Yueqiang, Feixiong Huang, Junming Xia, Cong Yin, Weihua Bai, Qifei Du, Xianyi Wang, Yuerong Cai, Wei Li, Guanglin Yang, and et al. 2023. "GNOS-II on Fengyun-3 Satellite Series: Exploration of Multi-GNSS Reflection Signals for Operational Applications" Remote Sensing 15, no. 24: 5756. https://doi.org/10.3390/rs15245756