FY-3 (FengYun-3) 2nd Generation Polar Orbiting Meteorological Satellite Series
The FY-3 series of CMA/NSMC (China Meteorological Administration/National Satellite Meteorological Center) represents the second generation of Chinese polar-orbiting meteorological satellites (follow-on of FY-1 series). The FY-3 series represents a cooperative program between CMA and CNSA (China National Space Administration); it was initially approved in 1998 and entered full-scale development in 1999. Key aspects of the FY-3 satellite series include collecting atmospheric data for intermediate- and long-term weather forecasting and global climate research. 1) 2) 3) 4) 5) 6) 7) 8) 9) 10) 11) 12) 13) 14)
The overall objectives of the FY-3 series are:
• To provide global measurements of 3-D temperature and moisture soundings of the atmosphere, and to measure cloud and precipitation parameters in support of NWP (Numerical Weather Prediction).
• To provide global imagery of large-scale meteorological and/or hydrological events and biosphere environment anomalies
• To provide geophysical parameters in support of global change and climate monitoring.
• To provide global and local meteorological information for specialized meteorological users working in services of aviation, marine, etc.
• To collect and relay environmental data from the ground segment.
• The FY-3 operational phase will have two polar-orbiting satellites in service (one in the AM and one in the PM orbit, payload will be different for AM/PM satellites, time slots could be coordinated through WMO).
There are two development phases considered for the FY-3 series
1) Experimental phase in the time period 2008-2010 with two spacecraft launches. These satellites have only limited sounding capabilities.
- FY-3A launch on May 27, 2008, LTDN (Local Time on Descending Node) = 10:00 hours.
- FY-3B launch on Nov. 4, 2010, LTDN = 14:00 hours.
2) Operational service phase beyond 2012. These satellites will have enhanced sounding and imaging capabilities.
- FY-3C launch on Sept. 23, 2013, LTDN =10:00 hours.
- FY-3D launch on November 14, 2017, LTDN = 14 hours.
- FY-3E launch on July 4 2021, LTDN = 10 hours.
The CMA plans call for a constellation of two FY-3 spacecraft in orbit, one in the morning slot (AM) and one in the afternoon slot (PM).
Table 1: Overview of FengYun-3 spacecraft series of CMA/NSMC
In comparison with FY-1 spacecraft series, the principal improvements in the FY-3 series include:
1) Atmospheric sounding capacity
2) Microwave imaging capacity
3) Optical imaging with spatial resolution from 1 km to 250 m
4) Atmospheric composition detecting capacity
5) Radiation budget measuring capacity
6) Global data acquisition from within one day to within two to three hours.
The FY-3 series represents in fact a new chapter in the history of the Chinese meteorological satellites and satellite meteorology. The FY-3 series provides global air temperature, humidity profiles, and meteorological parameters such as cloud and surface radiation required in producing weather forecasts, especially in making medium numerical forecasting.
The FY-3 series satellites monitor large-scale meteorological disasters, weather-induced secondary natural hazards and environment changes, and provides geophysical parameters for scientific research in climate change and its variability, climate diagnosis, and predictions. The FY-3 series renders global and regional meteorological information for aviation, ocean navigation, agriculture, forestry, marine activities, hydrology, and many other economic sectors.
Note: The FY-3C spacecraft is equipped with all of the 11 payloads, but MWTS is upgraded to MWTS-II, MWHS to MWHS-II, and a new payload, GNOS (GNSS Occultation Sounder), is on board FY-3C. MWTS-II will increase the channels from 4 to 13, and MWHS-II will increase the channels from 5 to 15. GNOS will improve the measured temperature and moisture profiles in the upper atmosphere. 15)
Tentative Schedule for Future FY LEO Series:
For the FengYun LEO satellites, after FY-3A/B, the future FY-3 models (FY-3C/D/E/F) have been approved. CMA plans to develop certain observational capabilities for the follow-up models, for instance, the WindRAD for sea winds, the GAS for greenhouse gases absorption measurement. The atmospheric sounding shall be enhanced by replacing the current IRAS with HIRAS (Hyperspectral Infrared Atmospheric Sounder), and by the deployment of radio occultation sounder GNOS. Also, there is a plan to develop a rainfall measurement satellite: FY-3RM (2019), that shall carry Ku/Ka band radar, microwave sounding and imaging instruments. 16)
Feasibility Study on FY-3 Use of Early Morning Orbit: FY-3 series serves at least for another 15 years with the additional four satellites. Sixteen (16) improved or new instruments will be configured on FY-3C/D/E/F. It is unrealistic for CMA to fly three orbits (AM, PM, and Early Morning) at the same time. Since FY-3C & 3D are being manufactured now, there is no chance to make them changed for the Early Morning orbit. FY-3E is possibly the only opportunity for CMA to fly early morning orbit before 2020.
Table 2: FY-3C/D/E/F payload configuration
The FY-3 series spacecraft are being designed and developed at SAST (Shanghai Academy of Spaceflight Technology). The spacecraft structure is a hexahedron of 4.4 m x 2.0 m x 2.0 m in stowed configuration and 4.4 m x 10 m x 3.8 m in the deployed state. The total spacecraft launch mass is estimated to be 2450 kg. The FY-3 features one solar panel mounted on one side of the satellite's main body (making the span length of the satellite 10 m in flight configuration). The attitude control of the satellite employs three-axis stabilization (bias momentum control) with a pointing precision of 50 m on the ground. The ADCS (Attitude Determination and Control Subsystem) employs a star sensor for attitude sensing.
The FY-3 bus contains three major modules: a service module, a payload module, and a propulsion module. The spacecraft design life is 3 years.
Table 3: System design parameters of the FY-3 satellite series
Launch: A launch of the first satellite in the series, FY-3A, took place on May 27, 2008. The spacecraft was launched on a LM-4C launch vehicle from the Taiyuan Launch Center. 17)
Orbit of FY-3A: Sun-synchronous near-circular orbit, average altitude of 836.4 km, inclination of 98.75º, period = 101.49 min, local solar time on descending node at 10:10 hours, 14.1735 orbits/day, tropical cycle of about 6 days.
Launch: The FY-3B spacecraft was launched on Nov. 4, 2010 (UTC). The spacecraft was launched on a LM-4C launch vehicle from the Taiyuan Launch Center.
Orbit of FY-3B: Sun-synchronous near-circular orbit, average altitude of 836.4 km, inclination of 98.75º, period = 101.49 min, local solar time on ascending node at 13:30 hours, 14.1735 orbits/day, tropical cycle of about 6 days.
Orbit of FY-3C: Sun-synchronous near-circular orbit, average altitude of 836 km, inclination of 98.75º, period = 101.49 min, LTDN (Local solar Time on Descending Node) at 10:00 hours, 14.1735 orbits/day, tropical cycle of about 6 days.
RF communications: The spacecraft communications links are S-band, L-band and X-band. Commands are via S-band only. Command and telemetry links are active in parallel. The S-band section of the communications subsystem provides primary telemetry and command (TT&C) service to and from FY-3A ground stations. The L-band and X-band section of the communication subsystem provide the science and engineering data downlink for the FY-3A common spacecraft.
Three modes of operation are provided:
1) DPT (Delayed Picture Transmission) - a direct playback mode. All the stored science and engineering data onboard (except the MERSI data) is transmitted in high data rate at 110 Mbit/s, to the NSMC national ground playback stations (Beijing, Guangzhou, Urumuqi, Jamusi, and Kiruna) whenever the satellite is passing over the acquisition range of these stations. The transmission band frequency will be within the range of 8025 - 8400 MHz, encoding: CONV (7, ¾).
2) MPT (Mission Picture Transmission). This mode provides the direct broadcast in X-band. The main function of this data format is for real-time broadcasting of the science and engineering data of the MERSI instrument with a data rate of 18.7 Mbit/s to any receiving station within view of the spacecraft. The broadcasting band frequency is in the range 7750-7850 MHz, QPSK modulation, encoding: CONV (7, ¾).
3) AHRPT (Advanced High Resolution Picture Transmission) -also referred to as HRPT. The AHRPT transmission band frequency is within the frequency range of 1698-1710 MHz at the data rate of 4.2 Mbit/s (real-time global broadcasting). The modulation is QPSK (Quadra‐Phase Shift Keying), encoding: CONV (7, ¾), real-time broadcasting. 20)
Launch: The FY-3D spacecraft was launched on 14 November 2017 (18:35 UTC; 2:35 Beijing Time on 15 Nov. 2017) on a LM-4C launch vehicle from the TSLC (Taiyuan Satellite Launch Center, China. 21)
Orbit of FY-3D: Sun-synchronous near-circular orbit, average altitude of 836 km, inclination of 98.75º, period = 101.49 min, LTAN at 14:00 hours.
From the view of consistency of meteorological satellite sequence, FY-3D satellite will replace FY-3B which has been operated for 8 years in space, launch network observation with FY-3C, and stand on duty with FY-4A at 800 km and 36,000 km, respectively, constituting the new-generation high-low orbit meteorological satellite constellation.
Launch: The FY-3E spacecraft was launched on 4 July 2021 at 23:28 UTC (corresponding to 7:28 Beijing Time on 5 July) according to CASC (China Aerospace Science and Technology Corp.) on a Long March 4C vehicle from JSLC (Jiuquan Space Launch Center) in China. 22)
Orbit: Sun-synchronous near-circular orbit, altitude of ~ 800 km, inclination of 98.7º. FF-3E crosses the equator in the early morning, local time, making it the first civilian weather satellite to launch directly into an early morning orbital plane.
The China Meteorological Administration said Fengyun 3E, designed for a service life of at least eight years, will fill a gap in the early morning orbit.
Chinese officials said the Fengyun 3E satellite joins two other Chinese polar-orbiting weather observatories, Fengyun 3C and Fengyun 3D, flying in mid-morning and afternoon orbits. Together, the satellites provide global weather measurements to feed into numerical weather prediction models at six-hour intervals.
Fengyun 3E hosts 11 payloads, including three brand new weather monitoring instruments, according to CMA. - The satellite’s payload includes microwave and infrared sounders to measure temperature and moisture profiles in the atmosphere, an instrument to derive atmospheric conditions and ocean winds using reflected navigation satellite signals, and a spectral imager to observe clouds and measure sea surface temperatures, a driver of tropical cyclone development.
Figure 2: A Chinese Long March 4C rocket takes off carrying the Fengyun-3E weather satellite (image credit: Xinhua)
Table 4: Overview of FY-3 LEO constellation missions of CMA as of fall 2015 (Ref. 33)
To support global NWP (Numerical Weather Prediction) services within the coordination framework of CGMS (Coordination Group for Meteorological Satellites), Dr. Zheng made a commitment in WMO (World Meteorological Organization) EC-66 in 2014 23) that CMA will adjust its satellite plan to develop an early morning orbit mission. Hence, the FY-3E mission has now been changed as an early morning orbit satellite rather than the previously assigned morning orbit (AM).
Figure 3: Schematic illustration of the FY-3A spacecraft (image credit: CMA/NSMC)
• July 12, 2021: With more than 30 years of Earth observational data freely available to international partners, the Fengyun Meteorological Satellite program works as part of Earth's operational observation system, along with the United States' National Oceanic and Atmospheric Administration satellites and Europe's polar orbiting meteorological satellite series to provide a more complete picture weather events and their global impacts. 24)
- To highlight the Fengyun satellites' data applications and to encourage further research among domestic and international collaborators, Advances in Atmospheric Sciences published a special issue titled, "Fengyun Meteorological Satellites: Data, Application and Assessment," on 10 July, 2021. It's the first time international communities' evaluation and application of Fengyun satellites are collectively published in a journal.
- The special issue is a culmination of research initiated at a 2019 conference for international users to develop a comprehensive, integrated approach for exchanging ideas and promoting global applications of the satellite data, according to Peng Zhang, the deputy director of the National Satellite Meteorological Center of the China Meteorological Administration. More than 200 people representing more than 30 countries attended. Since then, international users have applied the data in various research projects, and Zhang said the intention is for collaborations to grow as the data capabilities expand.
- "In the last decade, great efforts have been made to improve the performance of the satellites and their on-board instrumentation," said Zhang, who organized the special issue. "With extensive, multi-modal observational capabilities on Fengyun satellites, international communities have and will continue to make use of this data."
- Such capabilities include image navigation, radiometric calibration, multiband optical imaging, atmospheric sounding, microwave imaging, hyperspectral trace gas detection, full-band radiation budget measuring and more — in short, an extensive list of ways to monitor weather events and atmospheric changes of Earth. Zhang also co-authored a data description paper (Ref. 26), which summarizes not only the data available, but how international users can access it.
- The critical factor, Zhang said, is in how these data can be applied. The rest of the special issue features work undertaken in each of the 2019 conference's sections: retrieval algorithms, used to interpret raw data; products validation, which cross-references satellite data with earth-based observations; numerical weather predictions, or how to predict future weather using models of current atmospheric conditions; and climate and environmental predictions, which involves using satellite data to estimate surface effects of atmospheric changes.
- On 4 July, Fengyun 3E, the world's first early morning orbit weather satellite was launched, and it will improve global weather forecast by filling in the data gap in a certain time of a day and assist in achieving 100 percent global data coverage every six hours.
- "Fengyun satellites will continue to play an important role in Earth sciences in the future, especially as the international community continues to collaborate and apply this data to research that benefits us all," Zhang said. "The new epoch for comprehensive Earth observations has begun."
• According to OSCAR of WMO, the FY-3D satellite is operational as of 19 August 2020.
• On 8 Dec. 2017, the FY-3D spacecraft acquired the first visible light image and transmitted it to the ground. 27)
- From mid-December, FY-3D will embark on a half-year in-orbit testing, and is on track to complete operational application before the flood season in 2018. At that time, it will form network observation operation with FY-3C.
- Accordingt to Yang Jun, director of NSMC (National Satellite Meteorological Center), FY-3D boasts a very high imaging quality judged by the detail and texture of the image. Marine and land information of South China Sea, the Yarlung Zangbo River, Qinghai-Tibet Plateau, and Northwest Desert are all visible from the image, as well as endemic information in salt lake, alluvial fan, and snow cover.
- The mission of FY-3D’s first image was acquired by satellite ground stations in Guangzhou, Urumqi, and Kiamusze. At present, reception equipment in 5 ground stations at home and abroad in charge of global satellite data reception and transmission is in functional state. Especially the activation of Antarctica satellite data reception station ensures that 90% global observation data is transmitted to China 80 minutes upon observation. Satellite-ground data transmission rate has augmented by 30%. The computing capacity is up by 17.5 times and data storage capacity has multiplied by about 10 times.
Figure 4: The first visible light image of FY-3D (true color image of 3 channels of MERSI-2), showing marine and land information of the South China Sea (image credit: CMA)
• The FY-3C mission is operational in 2018.
• According to WMO, the FY-3C mission is operational in 2017 with the following exemptions: 28)
- MWTS-2 failed on 2 February 2015. Operational service was suspended on 31 May 2015 for anomaly investigation. Recovered from 30 July onwards.
- Power supply limitation has led to turn off MERSI and MWTS on 31 May 2015.
Figure 5: Global nephogram (image of clouds) of the VISR (Visible-Infrared Scanning Radiometer) on FY-3C (image credit: CMA)
• December 2016: Observations from MWHS-1 on board FY-3B and its more advanced successor, MWHS-2, on board FY-3C have been received at the UK Met Office since 2012 and 2014, respectively. Since then, both instruments have been the subject of several validation studies conducted internally at the Met Office and in collaboration with ECMWF (European Centre for Medium-Range Weather Forecasts). These studies concluded that observations from MWHS-1 and MWHS-2 183 GHz channels are, once appropriately bias corrected, of a quality matching well established operational instruments of similar sounding capability. 29)
- Several low and high resolution full system experiments showed the benefit of adding MWHS-1 and MWHS-2 observations to the global model. As a consequence, MWHS-2 has been successfully integrated into parallel suite 37 in November 2015, and has been assimilated in operations since March 2016, while MWHS-1 has been successfully integrated to the parallel suite 38 due to become operational on November 1, 2016.
- MWHS-2 operational monitoring showed the presence of a small residual bias in channels 11 and 12, and recurrent transient rises of temperature that are correlated to large bias changes affecting the channels 13 and 14. Nevertheless, forecast sensitivity to observations impacts analyses confirmed that MWHS-2 contributes to a significant level to the reduction of model forecast errors.
- Work is currently under way to implement the assimilation of MWHS-2 183 GHz channels over land. The addition of land observations is expected to further reduce forecast errors. — Finally, a bilateral Met Office-ECMWF evaluation of FY-3C MWRI data will lead the way to pre-operational testings in 2017.
• The FY-3A spacecraft was retired on January 5, 2015, ending the global image coverage service. FY-3A provided a substantial contribution to ocean and ice monitoring, climate monitoring - and a significant contribution to atmospheric chemistry and space weather. 30)
- FY-3A mission instruments: MWRI failed soon after launch; IRAS failed in October 2008 (inactive); SBUS failed in December 2008 (inactive); ERM-1 failed in May 2008 (inactive); MWTS-1 failed in December 2012 (inactive).
• The FY-3B spacecraft is operating in 2016 providing operational meteorology. 31)
- FY-3B mission instruments: ERM-1 failed in August 2011 (inactive).
• The FY-3C spacecraft and its instruments are operating in 2016. 32)
- FY-3C mission instruments: MWTS-2 failed on Feb. 2, 2015. Operational service suspended on 31 May 2015 for anomaly investigation. Recovered from 30 July onwards.
Figure 6: FY-3 instrument status as of November 2015 according to Ref. 33)
Figure 7: In-orbit FengYun Satellites(6/7) (6 operational, 1 retired) as of fall 2015 (image credit: CMA) 33)
• Feb. 2015: A new methodology is developed to detect the cloud structures at different vertical levels using the dual oxygen absorption bands located near 60 GHz and 118 GHz, respectively. Observations from MWTS (Microwave Temperature Sounder) and MWHS (Microwave Humidity Sounder) on board the recently launched Chinese FengYun-3C satellite are used to prove the concept. It is shown that a paired oxygen MWTS and MWHS sounding channel with the same peak weighting function altitude allows for detecting the vertically integrated cloud water path above that level. A cloud emission and scattering index (CESI) is defined using dual oxygen band measurements to indicate the amounts of cloud liquid and ice water paths. The CESI distributions from three paired channels reveal unique three-dimensional structures of clouds and precipitation within Super Typhoon Neoguri that occurred in July 2014. 34)
• Status of FY-3 satellite series in January 2015: 35)
- FY-3A (launch on May 27, 2008): Only reduced operations are possible in 2015. MWRI failed soon after launch; IRAS failed in October 2008; SBUS failed in December 2008; ERM failed in May 2010; MWTS failed in December 2012.
- FY-3B (launch on Nov. 4, 2010): The FY-3B spacecraft and its payload are operating nominally in 2015.
- FY-3C (launch on Sept. 23, 2013): The FY-3C spacecraft and its payload are operating nominally in 2015.
• October 2014: FY-3C/MERSI has some remarkable improvements compared to the previous MERSIs including better SRF (Spectral Response Function) consistency of different detectors within one band, increasing the capability of lunar observation by space view (SV) and the improvement of radiometric response stability of solar bands. During the In-orbit verification (IOV) commissioning phase, early results that indicate the MERSI representative performance were derived, including the signal noise ratio (SNR), dynamic range, MTF, B2B registration, calibration bias and instrument stability. The SNRs at the solar bands (Bands 1–4 and 6-20) was largely beyond the specifications except for two NIR bands. 36)
• The FY-3A and FY-3B spacecraft and their payloads are operating nominally in 2013 (Ref. 39).
The FY-3 project conducted cross-calibrations between the MWTS/FY-3 channels with those of the AMSU-A and AMSU-B channels of the NOAA fifth-generation satellites (NOAA-15, -16, -17, -18 and -19) using the RM (Ray-Matching) method over the South Pole and North Pole study area in 2011. 39)
The results show that the in-orbit calibrations of AMSU-A on the fifth-generation NOAA satellites are identical with averaging errors less than 0.45 K, except the channel 8, in which the averaging error is up to -1.53 K. No obvious impact of solar illumination on AMSU-A/NOAA channels was found. - The in-orbit calibrations of MWTS/FY-3 channels are basically consistent with those of the AMSU-A/NOAA-19 channels, and a small influence of solar illumination on MWTS/FY-3B channel 4 was observed.
Large in-orbit calibration discrepancies were found between the MWHS/FY-3 channels and the AMSU-B/NOAA-16 channels, especially in MWHS/FY-3A channel 5. Strong influences of solar illumination on MWHS/FY-3 channels 3, 4 and 5 were observed.
• The FY-3A and FY-3B spacecraft and their payloads are operating nominally in 2012. 40)
- On 16 December 2011, sounding data from FY-3B began to be received and test dissemination started on EUMETCast. The new products will be made available to EUMETSAT Member States on January 24, 2012. This is in addition to the data already received and disseminated from FY-3A since the end of 2010. 41)
The addition of FY-3B data to EUMETCast follows discussions between EUMETSAT and CMA. During a bilateral meeting between the two organizations in May 2011 in Geneva, CMA agreed to add FY-3B data to the FY-3A data it already shares with EUMETSAT and its Member States.
• On June 2, 2011, the FY-3B spacecraft started its operational service after finishing a six-month commissioning period (the spacecraft was launched on Nov. 4, 2010). The operational service was handed over to CMA on May 27, 2011. The FY-3B will join the FY-3A to create a comprehensive weather satellite system. 42)
The MWRI instrument of FY-3B is providing continuous and stable data sets since launch. Compared with the MWRI instrument on FY-3A, the MWRI instrument on FY-3B features a higher stability and a much lower nonlinearity. 43)
• In Jan. 2011, the FY-3B spacecraft is on-orbit (launch Nov. 4, 2010, in the afternoon orbit). All 11 instruments of the payload have been switched on. The spacecraft and its payload are currently in their commissioning phase conducted by the NSMC (National Satellite Meteorological Center) of CMA. 44) 45)
• The FY-3A spacecraft and its payload are operating nominally in 2011. 46)
• On Nov. 7, 2010, a first image of the VIRR instrument was obtained from the FY-3B spacecraft. 47)
• The FY-3A spacecraft and its payload are operating nominally in the fall of 2010. 48)
• After launch (May 27, 2008) the spacecraft and its payload were in the commissioning phase. However, in the following months, FY-3A has served the Beijing 2008 Olympic Games and the flood season in 2008 at the same time.
Figure 8: Typhoon Fung-wong monitored by the MERSI instrument of FY-3A on 27 July, 2008 (image credit: NSMC)
Figure 9: Total ozone in DU (Dobson Units) monitored from TOU on Nov. 1, 2008 (image credit: NSMC)