In-orbit Validation of SEM-II onboard FengYun-3E
doi: 10.11728/cjss2026.05.2025-0226 cstr: 32142.14.cjss.2025-0226
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Abstract: The new generation of Space Environment Monitor (SEM), SEM-II, onboard the Chinese meteorological satellite, FengYun-3E, has the ability to measure the charged particle flux with particle energy from 30 eV to 300 MeV in multi-directions, the satellite surface potential, the radiation dose in sensors, and the geomagnetic field variations. The space environment detections derived from SEM-II can be utilized for satellite security designs, scientific studies, development of radiation belt models, and space weather event monitoring or disaster warning. In this paper, we introduce the SEM-II’s instrument characteristics, interpret the in-orbit calibration algorithm, perform the quantitative test to check the particle and the magnetic field detections’ biases by the cross-calibration methods, and do the qualitative tests to check whether the radiation dose and the surface potential detections follow the nature law of space environment by comparing with the historical records. The results show that the uncertainties of the particle detections are less than 20%, the uncertainties of the magnetic field detections are about 1%, the radiation dose and the surface potential detections coincide with the historical records and the space environment knowledge. The instruments’ responses to the space weather events are also presented.
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Key words:
- FengYun-3E /
- Space environment /
- Radiation effects /
- Energetic particles /
- Space technology
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Figure 7. Geomagnetic field map from FY-3E_SEM-II_MFD compared with IGRF13. The way for these maps’ generation is like that in Fig. 5
Table 1. Instruments specifications of FY-3E/SEM-II
Instrument name Observation object Installation geometry Sampling rate Sensitivity Channels High energy particles detector Integrated particle flux 3 directions in –X/Y/-Z with each direction’s view field ~ 40° 0.5 Hz 5% (ΔN/N) 6 energy bands for proton in 3-300 MeV;
5 energy bands for electron in 0.15-5.7 MeVMedium energy proton detector Integrated proton flux 18 directions with each direction’s view field ~ 20° 0.5 Hz 5% (ΔN/N) 12 energy bands for proton in 30 -5000 keV Medium energy electron detector Integrated electron flux 18 directions with each direction’s view field ~ 20° 0.5 Hz 5% (ΔN/N) 8 energy bands for electron in 30-600 keV Radiation dose detector Total radiation dose 3 probes installed on the interior surface of the outer wall of the satellite in X/Y/-Z 1/60 Hz 2 rad (Si) Each probe has 2 channels: one’s range is for 3×104 rad (Si), the other’s range is for 5×103 rad (Si) Surface potential detector Surface potential Relative Surface Potential Detector (RSPD) has 2 detectors: one faces to the night side, the other faces to the day side; Absolute Surface Potential Detector (ASPD)’s detail can be found in section 1.1.5 0.5 Hz <15 V RSPD has 2 channels; ASPD’s channels are illustrated in Figure 3 Magnetic field detector Magnetic field 6 sensors deployed on the satellite’s truss 50 Hz 0.1 nT Each sensor has three orthogonal channels to detect the magnetic field vectors Table 2. Statistics for the particle inter-comparisons (FY-3E vs. N-19) in Fig. 6
Time Correlation coefficient Slope Average Relative Deviation (ASTD) Spots number FY-3E HEP –X vs. N-19 MEPED90: 3-5 MeV Jul. 2021 0.94 1.10 20.22% 1971 Aug. 2021 0.95 1.15 23.35% 1957 Sept. 2021 0.96 1.15 20.39% 1953 FY-3E HEP –Z vs. N-19 OMNI: 35 - 275 MeV Jul. 2021 0.99 0.93 19.92% 2065 Aug. 2021 0.99 0.86 17.03% 2077 Sept. 2021 0.99 0.85 17.74% 2077 FY-3E HEP –X vs. N-19 MEPED90: 0.1 - 1.1 MeV Jul. 2021 0.96 1.14 23.46% 325 Aug. 2021 0.98 1.19 24.60% 326 Sept. 2021 0.99 1.17 24.41% 442 FY-3E HEP –X vs. N-19 MEPED90: 0.3 - 1.1 MeV Jul. 2021 0.96 0.92 17.75% 325 Aug. 2021 0.97 0.98 13.13% 326 Sept. 2021 0.99 0.94 10.88% 442 FY-3E MEP –X vs. N-19 MEPED90: 80 - 240 keV Jul. 2021 0.92 0.86 24.69% 1600 Aug. 2021 0.93 0.91 23.85% 1714 Sept. 2021 0.94 0.93 21.38% 1837 FY-3E MEP –X vs. N-19 MEPED90: 240-800 keV Jul. 2021 0.95 0.99 20.87% 2089 Aug. 2021 0.96 1.05 20.04% 2040 Sept. 2021 0.96 1.05 19.29% 2101 FY-3E MEE vs. N-19 MEPED00: 30-100 keV Sept. 2021 0.97 0.99 13.2% 1231 FY-3E MEE vs. N-19 MEPED90: 100-300 keV Sept. 2021 0.98 1.00 15.9% 1231 -
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