FY-1 (FengYun-1) 1st Generation Polar Orbiting Meteorological Satellite Series
FengYun (FengYun = wind and cloud) is a meteorological satellite series of China, organized by CMA (China Meteorological Administration). Within the meteorological program, the odd-numbered satellites (FengYun-1 or simply FY-1) refer to the polar-orbiting LEO series, while the even-numbered S/C (FY-2, FY-4, etc.) refer to the GEO series. 1) 2)
The first generation LEO satellite (FY-1) series consists of a total of four spacecraft (FY-1A, -1B, -1C, and -1D). The funding body in China is the Ministry of Aerospace, while CMA (China Meteorological Administration) is the agency authorized and empowered to administer the national meteorological service in the governmental capacity, and is charged with the organizational arrangement and coordination of national meteorological affairs.
NSMC (National Satellite Meteorological Center) is the scientific research and operational facility affiliated to the China Meteorological Administration. The main functions of NSMC include:
• To formulate and draft strategy and development program for China's meteorological satellites (space segment)
• To build up the ground system for China's meteorological satellites
• To conduct scientific research on meteorological satellite and satellite meteorology
• To be responsible for receiving, processing, distribution and application of foreign and China's meteorological satellite data.
NSMC, founded in 1971, maintains facilities to operate and monitor the meteorological satellites of China, to acquire the data of the satellites, and to archive and distribute the meteorological data (general service provision). NSMC operates three ground stations, those of Beijing, Guangzhou, and Urumqi for data acquisition.
The NCC (National Climate Center) of CMA (China Meteorological Administration) was founded in January 1995. NCC is China's national research center responsible for monitoring and assessment of all aspects of climate change. NCC functions also as China's regional WMO climate center. For this reason, CMA created a new entity under NCC supervision, the BCC (Beijing Climate Center), in March 2003.
Table 1: Overview of the FY-1 polar-orbiting satellite series (1st generation)
FY-1A/1B (FenYun-1A and -1B spacecraft)
The FY-1 series satellite program was initiated in 1977. The S/C (FY-1A and FY-1B) were designed and built by the Shanghai Institute of Satellite Engineering, part of CAST (China Academy of Space Technology); their payloads were developed by the Shanghai Institute of Technical Physics (SITP), part of CAS (China Academy of Sciences).
Both S/C are similar in design. The satellite structure is a hexahedron of size: 1.4 m x 1.4 m x 1.2 m and a mass of 750 kg for FY-1A. The FY-1A bus was increased for the FY-1B satellite. Likewise, total spacecraft mass increased from 750 kg to about 880 kg. Both satellites are three-axis stabilized (attitude control is maintained by a combination of nitrogen cold gas thrusters and reaction wheels, attitude is sensed by gyros and horizon sensors) and powered by two solar arrays (about 3.5 m long each) with a combined rating of 800 W. Nickel-cadmium batteries are used for electrical power storage.
The launch of both S/C was performed by Long March 4 (CZ-4) boosters from Taiyuan, China.
• Launch of FY-1A on September 7, 1988
• Launch of FY-1B on September 3, 1990.
Orbit of FY-1A: Sun-synchronous polar orbit with an altitude of 900 km; inclination = 98.9º, equatorial crossing at 3:30 PM on a descending node, period = 102.86 min.
Orbit of FY-1B: Sun-synchronous polar orbit with an altitude of 900 km; orbital period = 102.86 minutes; inclination = 99.1º, eccentricity < 0.005; equatorial crossing at 7:50 AM.
Figure 1: Illustration of the FengYun-1 spacecraft (image credit: CMA)
Operational status of missions:
• FY-1A (launch Sept. 7, 1988). The S/C went into its predicted orbit and started to make observations on the same day. The imagery was all nominal with an observed SNR higher than the design value. After 39 days of operations, the FY-1A satellite suffered serious malfunctions in its attitude control system and was lost thereafter as a consequence. Another problem was observed on the instrument infrared detectors in form of water vapor contamination, causing the loss of the IR signal.
• FY-1B (launch Sept. 3, 1990). The S/C reached its predicted orbit and provided a considerably improved operations environment on the accuracy and stability of S/C attitude as well as for the observing instruments. However, after operations for half a year, the same attitude problems occurred as with the FY-1A S/C. This time around, ground operations were able to rescue the S/C. Observations were continued until late 1992 when again attitude problems brought the mission to an end.
Sensor complement: (MVISR)
MVISR (Multichannel Visible and IR Scanning Radiometer):
• To acquire global visible and infrared cloud images for weather forecasting
• To take images of the land surfaces for the monitoring of crops, vegetation, snow coverage, floods, etc.
• To measure the sea surface temperature (SST)
• To perform an ocean color experiment for the retrieval of chlorophyll distributions (bands 3 and 4).
MVISR is a five-channel optomechanical scanning instrument operated at 360 rpm. The optical system consists of co-axial and co-focal paraboloid primary mirrors with a 20 cm diameter. The beam splitters of the VIS/IR channels divide the incident radiation into TIR, NIR and VIS beams which are projected onto the respective detectors (HgCdTe, single element Si detector, and three-element Si detector). The optical scanner consists of an elliptical Beryllium-based plane mirror and a driving motor. The mirror rotating axis is 45º. IFOV of 1.2 mrad (1.1 km spatial resolution) in HRPT mode and 4 km resolution in APT mode; FOV=55.4º; swath width = 2,860 km. Instrument calibration of the infrared channels is provided by a reference blackbody and by cold-space views in each scan period. The calibration parameters are transmitted as part of every data record. The TIR detector (HgCdTe) is operated at 105 K (cooled by a radiation cooler).
Figure 2: MVISR characteristics
Communications in real-time. Capability of on-board data storage. The satellites provided data in three modes: HRPT (High Resolution Picture Transmission) at 665.4 kbit/s, APT (Automatic Picture Transmission), and DPT (Delayed Picture Transmission). The data formats of HRPT and APT are very similar to those of the NOAA series satellites (satellite attitude is included).6)
The FY-1 series ground segment consists of three ground stations located in Beijing, Guangzhou and Urumqi; a data processing center is at NSMC (National Satellite Meteorological Center). NSMC broadcasts the FY-1 orbital prediction via GTS so that users throughout the world may receive HRPT and APT data in real time. 7)
Table 2: HRPT/APT transmission channel characteristics of FY-1
FY-1C/1D (FengYun-1C and FengYun-1D spacecraft)
The FY-1C/1D spacecraft are upgraded versions of the FY-1B satellite. A major effort has been made to improve the S/C reliability. The satellite structure is a hexahedron with body dimensions of 1.42 m x 1.42 m x 1.2 m. The deployed length of the S/C is 10.5 m. There are two solar panels, each with a total collecting area of 9.58 m2 providing power of 250 W. The S/C is three-axis stabilized with a pointing accuracy of 0.4º. Two MVISR instruments (one redundant) are mounted on the nadir-facing side of the S/C. The S/C mass is 954 kg, the S/C design life is two years. 8) 9) 10) 11) 12) 13)
RF communications: The High Resolution Picture Transmission mode of FY-1C and FY-1D is named CHRPT (China HRPT or simply HRPT), implemented in S-band. The data rate of CHRPT is 1.3308 Mbit/s, the modulation is BPSK/Bi-phase,m the polarization is right hand circular, the EIRP = 39.4 dbm. The transmission frequency is 1700.5 MHz. The data format is very similar to that of HRPT of the NOAA satellites. The on-board data storage capacity is increased to 300 minutes of data take (compared to 60 minutes on FY-1A/1B). This offers the provision of a parallel (to CHRPT) low-rate data stream, once per day, of four selected channels with reduced resolution (3.1 km) data, the low-rate transmission rate is 88.72 kbit/s. The low-rate data is referred to as GDPT (Global Delayed Picture Transmission), while the ten-channel data with 1.1 km resolution from anywhere in the world is referred to as LDPT (Local Delayed Picture Transmission). There is no support provided for APT mode communications.
Table 3: Overview of CHRPT parameters
The China National Satellite Meteorological Center (NSMC) receives the CHRPT data in Beijing, Guangzhou and Urumqi ground receiving stations in real time. In addition, NSMC can receive global coverage data through four selected channels with reduced resolution (4 km) once per day (DGPT data), as well as 20 minutes orbit observation data through ten channels with original resolution at any region of the world.
Table 4: Overview of spacecraft parameters
Launch: A launch of FY-1D took place on May 15, 2002 from the Taiyuan Satellite Launch Center, along with Haiyang-1 (Ocean-1) on a LM-4B launch vehicle.
Orbit: Sun-synchronous polar orbit, altitude = 863 km, inclination = 98.79º, period = 102.3 minutes, eccentricity <0.005, the repeat period is 12 days. The local equatorial crossing time is for FY-1C and FY-1D is around 7 and 9 AM, respectively, on the descending node.
Some application examples of FY-1C and 1D data: Drought monitoring, snow cover and snow disaster monitoring, flood monitoring, forest and grassland fire monitoring, dust storm monitoring, sea ice monitoring, etc.
Operational status of missions:
• The FY-1D spacecraft and its payload are operating nominally in 2011. 16)
• In October 2010, the FY-1D spacecraft and its payload (MVISR) are operational. 17)
• The FY-1D spacecraft is operational in 2009.
• On Jan. 11, 2007, China destroyed the FY-1C spent/inactive satellite in an interception test causing an explosion and a lot of debris in a wide LEO corridor . Some 40 pieces of debris have been tracked and cataloged by NORAD. Some of these pieces have apogees as high as 3,500 km. As more and more debris is “discovered” it will be clear that more and more of space is threatened. However, even the debris already tracked will start to spread out with time and threaten more and more satellites.
According to press reports, the interceptor is believed to have been carried by a DF-21 IRBM (known as in the West as the CSS-5), a solid propellant, two stage missile of the Chinese Armed Forces. This test makes China the third country, after the USA and Russia, to have tested ASAT (Anti Satellite) weapons. For China, the interception test was a successful military technology demonstration. However, for the rest of the world, the interception test caused many concerns with regard to space debris spreading in the densely populated LEO environment; the test generated a lot of protest from all spacefaring nations. 18) 19) 20)
• The MVISR instrument of FY-1C spacecraft experienced a scanner synchronizing problem in January 2004, thereby ending the operational life of the instrument. The FY-1C spacecraft was decommissioned in late 2005. - Nominal operations are provided by the FY-1D spacecraft and instruments. 21)
Sensor complement: (MVISR, HEPD)
MVISR (Multichannel Visible and IR Scanning Radiometer):
MVISR was developed and built by SITP (Shanghai Institute of Technical Physics). MVISR is composed of the following elements: optical scanner, image information processor, radiant cooler and cooler controller. The upgraded MVISR is now a 10-channel instrument (the total number of bands was doubled for the -1C and -1D instruments form the previous -1A and -1B instruments).
The optomechanical instrument (whiskbroom scanning technique) has a scan mirror with a rotation rate of 360 rpm. The aperture of the optical system is 200 mm in diameter. The IFOV = 1.2 mrad, the nadir resolution of all channels is 1.1 km. The instrument FOV is ±55.4º (2800 km swath). The scan rate of MVISR is 6 lines/s, the total number of pixels of every scan line is 2048.
Figure 3: Illustration of the MVISR instrument (image credit: SITP)
Table 5: Spectral channels of MVISR
Table 6: Specification of the MVISR instrument
Figure 4: The first image in the northwest of China of FY-1D with high resolution at 1.1 km (image credit: CMA)
HEPD (High Energy Particle Detector):
The objective is to study the space environment: measurements include heavy ions composition, proton energy spectrum and high energy electron integrated flux. The detector was built by CSSAR (Center for Space Sciences and Applied Research) of CAS (Chinese Academy of Sciences). The detector can measure protons in the energy range from 4 to 300 MeV and electron flux of over 2 MeV in the Earth's inner radiation belt. CAS uses the space weather data to issue solar storm warnings, which are very useful in protecting orbiting spacecraft and in various terrestrial applications such as surge protection of a power grid.
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14) Information provided by Wang Xinmin of the Shanghai Institute of Technical Physics, Shanghai
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18) G. Forden, “A Preliminary Analysis of the Chinese ASAT Test,” URL: http://web.mit.edu/stgs/pdfs/A%20Preliminary%20Analysis%20of%20the...
21) Information provided by Chaohua Dong of CMA/NSMC (National Satellite Meteorological Center), Beijing
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.