Minimize FY-4

FY-4 (FengYun-4) Geostationary Meteorological Satellite Series

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FY-4 is CMA's (China Meteorological Administration) second-generation three-axis stabilized, geostationary meteorological satellite series, under development by CAST (China Academy of Space Technology). Two variants of spacecraft of the FY-4 (FenYun means "winds and clouds or storm" in Chinese) program are in planning, with one carrying optical sensors and the other carrying microwave sensors.

Compared to the current FY-2 geostationary meteorological satellite series, the performance of the FY-4 series has been considerably improved in terms of data amount, network transmission bandwidth, product type and quantity and archiving data and applications. The new generation FY-4 satellites are designed with an enhanced imagery scanning capability, desirable for monitoring small and medium scale weather systems. FY-4 is enabled with vertical atmospheric sounding and microwave detection capabilities to address 3D remote sensing at geostationary altitudes. The new FY-4 series is also enabled with solar observations for EUV (Extreme Ultraviolet) and X-ray monitoring, in a bid to enhance China's space weather watch and warning capability. 1)

Based on user requirements and technical feasibility, the missions of the FY-4 series include imagery, sounding, lightning mapping, and space environment monitoring. HRIT (High Rate Information Transmission), LRIT (Low Rate Information Transmission) data transmission, and DCP (Data Collection Platform) services are available for users. 2) 3) 4) 5)

In 2015, the Chinese government approved the NSIP (National Space Infrastructure Plan) covering also the meteorological program of LEO and GEO missions up to 2025. 6)

The geostationary FenYun-4 series consists of seven spacecraft:

• FY-4A (2016-2021)

• FY-4B (2018-2025)

• FY-4C (2020-2027)

• FY-4D (2023-2030)

• FY-4E (2027-2034)

• FY-4F (2030-2037)

• FY-4G (2033-2040)


Figure 1: Overview of the GEO meteorological launch program of CMA for the next decade (image credit: CMA)

Next to the first FY-4 missions with optical payloads, CMA is also planning for FY-4 missions with MW (Microwave) payloads as shown in Figure 1.


FY-4 Optical Series

The optical variant will include two satellites: FengYun-4 ‘East', which will cover a region including western China, the Indian Ocean, the Red Sea and the Middle East; and FengYun-4 ‘West', which will cover a region including middle and eastern China and the Pacific. The microwave variant FengYun-4 will cover China and its peripheral areas. The FY-4A mission is considered a pre-operational (pathfinder, or R&D) mission with the follow-on FY-4B, -4C spacecraft are considered operational missions. 7) 8) 9) 10) 11) 12) 13)

The main tasks are described as follows:

- a) To obtain the multi-spectrum and high-accurate quantitative images of the earth and clouds;

- b) To measure the humidity parameter of atmosphere;

- c) To enhance the ability of detecting the space weather and environment;

- d) To collect various earth environmental parameter;

- e) To broadcast images, weather products, and the devastating weather forecasting.


FY-4 spacecraft series

FY-2 spacecraft series

Spacecraft stabilization

Three-axis stabilized

Spin stabilized

Spacecraft design life

5-7 years

4 years

Observation efficiency



Observation capabilities

Imaging +Sounding + Lightning Mapping

Imaging only

Main instruments

AGRI (Advanced Geosynchronous Radiation Imager)
14 channels
Spatial resolution: 0.5-4 km
FD (Full Disk) imaging: 15 minutes
Rapid Scan:2.5 minutes

VISSR (Visible and Infrared Spin-Scan Radiometer)
5 channels
Spatial resolution:1.25-5 km
FD imaging: 30 minutes
Rapid Scan: 3-6 minutes

GIIRS:(Geostationary Interferometric Infrared Sounder)
913 channels
Spectral resolution: 0.8 to 1.6 cm-1
Spatial resolution:16 km

N/A (Not Applicable)

LMI(Lightning Mapping Imager)
SSP resolution:7.8 km


SEP(Space Environment Package)
High energy particles
Magnetic field: Solar X ray fluxes

SEM (Space Environment Monitor)
High energy particles

Table 1: Comparison of FY-4 and FY-2 key mission parameters




The FY-4 series of geostationary spacecraft are being designed and developed by CASC/SAST (China Aerospace Science and Technology Corporation/Shanghai Academy of Space Technology). The SAST-5000 bus features an attitude determination system relying on star trackers, inertial measurement systems and Earth/Sun sensors with reaction wheels acting as the primary attitude actuator, achieving a high pointing accuracy of 3arcsec at low jitter to keep the satellite in a precise Earth-pointed attitude. Internal communications on the satellite use the 1553B communications standard and high-speed SpaceWire which supports the data rates required by the instruments and allows for easy integration. Downlink of raw instrument data is completed in real time via a high-speed X-band terminal operating at 7.500 GHz.

1) Launch mass: ~5300 kg

2) Spacecraft stabilization: Three-axis stabilization

3) Attitude accuracy: 3 arcsec

4) Onboard communication bus: 1553B+SpaceWire

5) Raw data transmission : X-band

6) Output power: ≥ 3.2 kW

7) Spacecraft design life: 7 years.


Figure 2: Illustration of the FY-4A prototype spacecraft (image credit: CMA/NSMC, Ref. 12)


Launch: The FY-4A spacecraft was launched on December 10, 2016 (16:11:00 UTC) on a Long March 3B vehicle from the XSLC (Xichang Satellite Launch Center) in the Sichuan Province of southwest China. 14) 15)

Orbit: Geostationary orbit, altitude = 35786 km, longitude = 99.5º E.


Mission status:

• February 28, 2017: FengYun-4A, the first of China's second-generation geostationary orbiting weather satellites, has sent its first collection of images and data. SASTIND (State Administration of Science, Technology and Industry for National Defence) and CMA (China Meteorological Administration) published the images and data on Feb. 27, signaling the successful upgrade of China's meteorological system. 16) 17)

- The composite image of Figure 3 was acquired by the instruments AGRI (Advanced Geosynchronous Radiation Imager) and GIIRS (Geostationary Interferometric Infrared Sounder).

- "We achieved a very successful engineering development. Four major payload devices of the FengYun-4 satellite started up smoothly and captured the first batch of data. The quality of the images is great. The information gained is up to what is expected in terms of quality and is qualified for use," said Tian Yulong, chief engineer of SASTIND.


Figure 3: Composite image of Earth obtained from the FengYun-4A spacecraft (image credit: CNSA)



Sensor complement of FY-4A configuration: (AGRI, GIIRS, GLI/(LMI), SEP, DCS)

The sensor complement of the new generation satellites are designed with an enhanced imagery scanning capability, desirable for monitoring small and medium scale weather systems. It is enabled with vertical atmospheric sounding and microwave detection capabilities to address 3D remote sensing at high altitudes. It is also enabled with solar observations for extreme ultraviolet and X-rays, in a bid to enhance China's space weather watch and warning capability. 18)


AGRI (Advanced Geosynchronous Radiation Imager)

AGRI is of ABI (Advanced Baseline Imager) heritage to be flown on GOES-R of NASA/NOAA (launch of GOES-R on Nov. 19, 2016). AGRI is being constructed by Harris Corporation, formerly ITT Exelis of Fort Wayne, IN, USA. In May 2015, Harris Corp. of Melbourne, FL. acquired Exelis Inc. of Fort Wayne, IN. AGRI uses an off-axis telescope, two scan mirrors, 216 detectors in 14 spectral bands, and full-path on-orbit calibration. 19)


Band (µm)

Spatial resolution (km)



VNIR (Visible&Near Infrared)



S/N ≥ 90




S/N ≥ 200

Clouds, Fog



S/N ≥ 200


SWIR (Shortwave Infrared)



S/N ≥ 200




S/N ≥ 200

Cloud, Snow



S/N ≥ 200

Cirrus, Aerosol

MWIR (Midwave Infrared)

3.5-4.0 (high)


NEDT ≤ 0.7 K


3.5-4.0 (low)


NEDT ≤ 0.2 K

Land Surface

Water Vapor



NEDT ≤ 0.3 K

Water Vapor



NEDT ≤ 0.3 K

Water Vapor

LWIR (Longwave Infrared)



NEDT ≤ 0.2 K

Water Vapor, Cloud



NEDT ≤ 0.2 K

Sea Surface Temperature



NEDT ≤ 0.2 K

Sea Surface Temperature



NEDT ≤ 0.5 K

Cloud, Water Vapor

Table 2: Specification of the AGRI instrument

Legend to Table 2: S/N (Signal to Noise Ratio) is specified at 100% albedo, NEDT is specified at 300 K, except for the two water vapor channels, which are specified at 260 K. 20) 21)

AGRI is replacing the S-VISSR sensor, flown on the FY-2A to H series. AGRI is the primary instrument of FY-4A, has 14 channels and two observation modes. The temporal resolutions are 1 - 5 minutes over a regional domain and 15 minutes over the full-disk domain.

AGRI is a multispectral imager with a two-axis scanning geometry, vastly expanding previous capabilities by adding spectral channels, improving spectral and spatial resolution of imagery, and employing a much faster data acquisition scheme.


GIIRS (Geostationary Interferometric Infrared Sounder)

GIIRS, developed by National Space Science Center of CAS, will be the main payload on board of FY-4A satellite to monitor and measure internal constitution and precipitation parameters of the atmosphere cloud cluster. 22)


FY-4A (R&D)

FY-4B (Operational)

Spectral parameters (normal mode)

Range Resolution Channels
LWIR: 700-1130 cm-1 (14.3-8.85 µm)
S/MWIR: 1650-2250 cm-1 (6.06-4.44 µm)
VIS: 0.55-0.75 µm

Range Resolution Channels
LWIR: 700-1130 cm-1
S/MWIR: 1650-2250 cm-1
VIS: 0.55-0.75 µm

Spatial resolution

LWIR/S/MWIR : 16 km SSP (Sub-Satellite Point)
VIS : 2 km SSP


Operational mode

China area: 5000 km x 5000 km
Mesoscale area: 1000 km x 1000 km

China area: 5000 km x 5000 km
Mesoscale area: 1000 km x 1000 km

Temporal resolution

China area < 1 hr
Mesoscale area < ½ hr

China area < 1 hr
Mesoscale area < ½ hr

Sensitivity (mW/m2 sr cm-1)

LWIR: 0.5 -1.1
S/MIR: 0.1-0.14
VIS: S/N> 200(ρ=100%)

LWIR: 0.3
S/MIR: 0.06

Calibration accuracy

1.5 K (3σ) radiation

1.0 K (3σ)

Calibration accuracy

10 ppm (3σ) spectrum

5 ppm (3σ)

Data quantization

13 bit

13 bit

Table 3: Key parameters of the GIIRS instrument

GIIRS can be used for vertical atmospheric sounding and it is the first high-resolution sounding sensor onboard the geostationary satellite. There are two observation modes of GIIRS. One mode is designed for China area, whose temporal resolution is 55 minutes and the coverage is 4500 x 4500 km. The other observation mode is mesoscale mode, whose temporal resolution is 30 minutes and the coverage is 1000 x 1000 km.

GIIRS is a MWIR (Mid-Wave Infrared)/TIR (Thermal Infrared) sounder with large detector arrays for simultaneous sounding of a larger area plus visible coverage support for cloud detection. The instrument operates by stepping dual scanning mirrors to subsequent scan positions with a specific dwell time over each location for data acquisition. On FY-4A, GIIRS covers 538 TIR channels and 375 MWIR channels, to be expanded to 1,188 detectors on the operational missions of FY-4B and forward.

The GIIRS detectors employ a deep data quantization of 13 bit and active coolers keep the 32 x 4 focal plane at a constantly low temperature for dark current reduction.

Data delivered by GIIRS is used to for atmospheric temperature profiles, cloud top height and temperature, sea surface temperature, specific humidity profiles, integrated water vapor measurements, cloud cover maps, land surface temperature, horizontal winds, total column ozone, and cloud type discrimination.


GLI (Geostationary Lightning Imager) — also called LMI (Lightning Mapper Imager)

The FY-4 spacecraft will carry the GLI (Geostationary Lightning Imager), which is the first lightning detection sensor on China's satellites. The GLI will be used to observe regional lightning activity in China. The GLI products will be used in forecasting and warning of convection precipitation, and studying of Earth's electric field. 23)

The objectives of the FY-4 GLI instrument are to measure the total lightning (both intracloud and cloud-to-ground) activity within its FOV (Field of View) continuously during both day and night. It will provide measurement with a resolution of 7.8 km at the subsatellite point and full disk continuously observed with a time resolution of about 2 ms. The CCD (Charge-Coupled Device) camera will operate at 777.4 nm to count flashes and measure their intensity. For that 777.4 nm is within the solar reflective band, a vicarious calibration using DCCs (Deep Convective Clouds) as stable targets is applicable.

The GLI 400 x 600 pixel CCD focal plane will stare continuously at storms from the FY-4 satellite. The GLI shall have a continuous monitoring capability across a coverage (9,000 km diagonal field-of-view) with a near-uniform round sample 8-14 km pixel footprint resolution.

Spatial resolution

about 6.8 km at SSP (Sub-Satellite Point)

Sensor size

400 x 300 x 2

Wave-length at center, band width

777.4 nm, 1nm±0.1nm

Detection efficiency


False-alarm ratio

< 10%

Dynamic range

> 100

SNR (Signal to Noise Ratio)

> 6

Frequency of frames

2 ms (500 frames/s)

Data quantization

12 bits

Measurement error


Table 4: Specification of the GLI


Figure 4: FOV view from the FY-4 GLI superimposed on one month (July, 2008) of lightning observations from the NASA LIS (Lightning Imager Sensor) on board the Tropical Rainfall Measuring Mission (TRMM/LIS) LEO satellite (image credit: CMA, NASA)


SEP (Space Environment Monitoring Package)

Monitoring of charged particles at platform level. Package of instruments for energetic particle detectors. Set of counters for electrons (0.4-4 MeV) and protons (1-165 MeV).

• High-energy Proton Detector: 8 channels in the energy range of 1-165 MeV; the FOV is conical at 60º.

• High-energy Electron Detector: 9 channels in the energy range of 0.4 - 4 MeV; the FOV is conical at 25º.

• Package of instruments including a FGM (Flux Gate Magnetometer), and radiation dosimeter and surface charging sensors. Dynamic range of FGM: ±0.01 to ±600 nT for each component, with resolution ±0.06 @ maximum of the dynamics.


DCS (Data Collection System)

Data collection from DCPs (Data Collection Platforms) in the ground segment. Two types of DCPs will be served: either regional, or international (i.e. migrating across the field of view of more geostationary satellites).



Ground segment:



Figure 5: New FY-4A ground segment: Elements & Layout (image credit: NSMC/CAS) 24)

FY-4A will provide 28 baseline products as shownin Table 5. All algorithm design and development have already been completed. The next step plans to use simulation data to validate the reliability of each algorithm.

Baseline Products of imager (AGRI) & LMI






Cloud Masks


Downward Shortwave Radiation: Surface


Cloud Type


Derived Motion Winds


Cloud Top Temperature


Lightning Detection


Cloud Top Pressure


Rainfall Rate /QPE (Quantitative Precipitation Estimation)


Cloud Optical Depth


Convective Initiation


Cloud Liquid Water


Tropopause Folding Turbulence Prediction


Cloud Particle Size Distribution


Sea Surface Temperature (skin)


Aerosol Detection


Fire/Hot Spot Characterization


Aerosol Optical Depth


Land Surface (Skin) Temperature


Downward Longwave Radiation: Surface


Land Surface Emissivity


Upward Longwave Radiation: TOA


Snow Cover


Upward Longwave Radiation: Surface


Space weather products


Reflected Shortwave Radiation: TOA



Baseline Products of sounder (GIIRS)


Atmospheric Temperature, Humidity and Ozone Profiles (Clear)


Atmospheric Temperature and Humidity Profiles

Baseline Products of SEP


Distribution of High Energy Particle Products


Intensity of Magnetic Field


Effects of Spatial Environment



Table 5: Overview of expected products for the FY-4A mission


1) "Brief introduction of FY-4 Satellites," CMA, Sept. 16, 2015, URL:

2) "FY-4 Series Satellites," NSMC, URL:

3) "CMA Report on Preparations for FY-4," CGMS-39, CMA-WP-06, St. Petersburg, Russia, Oct. 3-7, 2011, URL:

4) Peng Zhang, "Future Fengyun Observing System," 19th International TOVS Study Conference, 26 March – 1 April 2014, Jeju Island, Republic of Korea, URL:


6) Ruixia Liu, "Status of Current and Future Satellite Programs of China Meteorological Administration," The 1st KMA International Meteorological Satellite Conference, Seoul, Korea, November 16-18, 2015, URL:

7) "FengYun 4," Dragon in Space, April 3, 2012, URL:

8) "FY-4 Program," CMA, URL:

9) Jun Yang, "China's FengYun Meteorological Satellite Programs," 17th International TOVS Study Conferences, Monterey, CA, 14 - 20 April 2010, URL:

10) Peng Zhang, "The status and future plan of Yengyun(FY) meteorological Satelltes," March 5, 2012, URL:

11) Jun Yang, "The status and future plan of China's FengYun Meteorological Satellite Programs," 18th International (A)TOVS Study Conferences, Toulouse, France, 20 – 27 March 2012, URL:

12) Feng Lu, "CMA report on the current and future satellite systems," CGMS-42 (Coordination Group for Meteorological Satellites) plenary session, Guangzhou ,China, May 2014, URL:

13) Feng Lu, "Preparing a seamless transition towards FY-4," 4th Asia-Oceania Meteorological Satellite Users Conference, Melbourne, Australia, Oct. 9-11, 2013, URL:

14) "China launched next-generation geostationary meteorological satellite FY-4-01," Shanghai Daily, Dec. 11, 2016, URL:

15) Tomasz Nowakowski, "Long March 3B sends Fengyun-4A weather satellite into orbit," Spaceflight Insider, Dec. 10, 2016, URL

16) "China's Fengyun-4 delivers first round of imagery and data + Shijian-13 set to go in April," Satnews Daily, Feb. 28, 2017, URL:

17) "China-Weather Satellite/Images," China Central Television (CCTV), Feb. 27, 2017, URL:

18) Xiang Fang, "Preparation for FY-4A," WMO, Commission for basic systems open program area group on integrated observing systems, Expert Team on Satellite Utilization and Products, Eight Session, Geneva, Switzerland, April 14-17, 2014, URL:

19) "GEO-News around the world — FengYun-4," Dec. 30, 2015, URL:

20) Yongfang Zhang, Jungang Miao, Haibo Zhao, Guangbin Cui, Yan Shi, "A five-frequency band quasi-optical multiplexer for geostationary orbit microwave radiometer," Proceedings of IGARSS (International Geoscience and Remote Sensing Symposium), Munich, Germany, July 22-27, 2012

21) Hao Liu, Ji Wu, Shengwei Zhang, Jingye Yan, Lijie Niu, Cheng Zhang, Weiying Sun, Huiling Li, Bin Li, "The Geostationary Interferometric Microwave Sounder (GIMS): Instrument Overview and Recent Progress," Proceedings of IGARSS (International Geoscience and Remote Sensing Symposium), Vancouver, Canada, July 24-29, 2011

22) Weiying Sun, Hao Liu, Cheng Zhang, Shengwei Zhang, Ji Wu, "Design, Position Error Analysis and Adjustment of Antenna Array for Geostationary Interferometric Microwave Sounder," Proceedings of IGARSS (IEEE International Geoscience and Remote Sensing Symposium), Melbourne, Australia, July 21-26, 2013

23) Dongjie Cao, Fuxiang Huang, Xiushu Qie, "Development and Evaluation of detection algorithm for FY-4 Geostationary Lightning Imager (GLI) measurement," XV International Conference on Atmospheric Electricity, 15-20 June 2014, Norman, Oklahoma, USA, URL:

24) Caiying Wei, "Updates on Chinese Meteorological Satellite Programs," 6th Asia/Oceania Meteorological Satellite Users' Conference, Tokyo, Japan, Nov. 10, 2015, 2nd ISCC Meeting was held during Oct. 14-17, 2015, Beijing, China, URL:

The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (

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