Minimize FY-2 (FengYun-2)

FY-2 (FengYun-2) Geostationary Satellite Series

China began the development of its geostationary meteorological program in the 1980s. FengYun-2, or FY-2 (FenYun means "winds and clouds" in Chinese), is the geostationary meteorological satellite series of China, organized and operated by NSMC (National Satellite Meteorological Center) of CMA (China Meteorological Administration) and built by the Shanghai Institute of Satellite Engineering. China started its FY-2 development program in 1980.

Note: China adopted the following convention in the naming of its meteorological satellites: The odd number series such as FY-1, FY-3 stands for spacecraft in the polar orbiting satellite series, while the even number label such as FY-2, FY-4 designates the various generations of the geostationary series.

Spacecraft

Launch Date

Comment

FY-2A

June 10, 1997

Regarded as experimental S/C in GEO; FY-2A was retired in April 2000

FY-2B

June 26, 2000

Regarded as experimental S/C in GEO;

FY-2C

Oct. 19, 2004

Operational as of 2006; FY-2C is regarded as the first operational meteorological satellite mission (in GEO) of China

FY-2D

Dec. 8, 2006

Initially, it will function as backup to FY-2C

FY-2E

2009 planned

To replace operations of FY-2C

FY-2F

2011 planned

 

FY-2G

2013 planned

 

Table 1: Overview of first generation meteorological CMA spacecraft in GEO 1)


 

Spacecraft:

The FY-2 spacecraft are dual spin-stabilized at 100 rpm with a despun antenna platform (similar in design and operation to the GMS series of Japan). The FY-2 spacecraft bus is 2.1 m in diameter with a height of about 1.6 m (cylinder), S/C on-orbit mass = 593 kg. Power (280 W) is generated by surface-mounted solar cells. The observation objectives of the Asia-Pacific region are:

- Acquiring daylight visible cloud maps, day-and-night infrared cloud maps and water vapor distribution maps

- Data collection from meteorological, oceanic and hydrological observational platforms

- Broadcasting of stretched digital cloud maps, low resolution cloud maps and weather map information

- Obtaining cloud top and sea surface temperatures as well as the wind field distribution by data processing.

FY2_At Anchor0

Figure 1: Illustration of the FY-2 spacecraft

In 1994, the long-awaited Feng Yun 2 GEO meteorological spacecraft was to be launched and positioned at 105º E longitude. The first FY-2 satellite in the series, namely FY-2A, was undergoing final check-out on April 2, 1994, before being mated to its launch vehicle, when a fire and explosion erupted, destroying the vehicle. 2)


 

FY-2A (FengYun-2A)

A second identical satellite, also referred to as FY-2A, was built by the Shanghai Institute of Satellite Engineering and launched by a Long March 3 (CZ-3) booster from Xichang on June 10, 1997. The first imagery of S-VISSR was received on July 13, 1997. FY-2A data can be received by all international users.

On 8 April 1998, FY-2A ceased transmission of S-VISSR images, to resume for a few hours on 10 April, due to a problem with the S-band antenna on the spacecraft. CMA managed to regain Earth lock and ranging with the S-band antenna for 12 hours on 14 April 1998, but there were no regular S-VISSR retransmissions during the summer of 1998. However, CMA could still get raw image downlinks a few times per day, and they would make one full-earth picture on the ground each day, but not broadcast it. As of October 1998, CMA resumed a partial but regular communication service of six transmissions per day. The FY-2A spacecraft was finally retied in April 2000.

Orbit: Geosynchronous orbit at position: 105º eastern longitude.

Ground segment: The FY-2 program ground system consists of a CDAS (Command and Data Acquisition Station), a DPC (Data Processing Center), a SOCC (Satellite Operation Control Center), ranging stations (one primary station, three secondary stations including one in Australia), widely dispersed data collection platforms (DCP), MDUS (Medium-scale Data Utilization Stations) and SDUS (Small-scale Data Utilization Stations), as well as a ground communications system.


 

Sensor complement: (S-VISSR, DCS)

S-VISSR (Stretched - Visible and Infrared Spin-Scan Radiometer), an optomechanical system. Scanning modes: a) normal scanning; b) optional scanning; c) single line scanning. A picture frame (normal scanning) = 30 minutes, a scan (North-South) = 2500 steps.

Parameter

Visible

Infrared

Water vapor

Spectral band (µm)

0.55 - 1.05

10.5 - 12.5

6.2 - 7.6

No. of detectors/channels

4 (+4 spare)

1 (+1 spare)

1 (+1 spare)

Scan lines

2500 x 4

2500

2500

Spatial resolution

1.25 km x 1.25 km
IFOV=35 µrad

5 km x 5 km
IFOV=140 µrad

5 km x 5 km
IFOV = 140 µrad

Detectors

Si photodiode

HgCdTe

HgCdTe

Data quantization

6 bit

8 bit

8 bit

Noise performance

SNR=6.5 (albedo=2.5%)
SNR= 43 (albedo=95%)

NEDT=0.5-0.65 K
(300 K)

NEDT= 1 K
(300 K)

Scan step increment

140 µrad (N-S scanning)

Temporal resolution

30 minutes (frame time)

Table 2: Some characteristics of S-VISSR

The telescope collects radiation during each scan and focuses it on the detectors in the focal plane using primary and secondary mirrors. The Si photodiode detector array has four elements mounted normal to the scan direction, providing a 5 km wide instantaneous observation coverage on each scan line, matching the scan line width of the IR detectors with only one detector element. The HgCdTe detectors are cooled by radiation coolers to a temperature of 100 K. A complete scan of 20º x 20º, covering the full Earth disk, is obtained every 30 minutes by means of the S/C spin motion (100 rpm from E-W) and the step action (2500 steps from north to south) of the scan mirror.

The FY-2 ground segment (geostationary satellites) consists of the following facilities:

1) CDAS (Command and Data Acquisition Station)

2) DPC (Data Processing Center)

3) SOCC (Satellite Operations and Control Center)

4) Ranging stations (one primary and three secondary stations, including one in Australia)

5) DCPs (Data Collection Platforms)

6) MDUS (Medium-scale Data Utilization Station) and SDUS (Small-scale Data Utilization Station) stations.

Channel

Frequency

Modulation

Power

Bandwidth

S-VISSR

1687.5 MHz

PCM/BPSK, NRZ-M

57 dBm

2 MHz

LR-Wefax

1691.0 MHz

AM/FM

57 dBm

260 kHz

S-Fax

1699.5 MHz

AM/FM

46 dBm

26 kHz

Table 3: Some downlink characteristics of FY-2A

FY-2 series communication: The FY-2 satellites broadcast their data to the ground, this includes S-VISSR, WEFAX and S-FAX data. S-VISSR data are received at MDUS, while WEFAX and S-Fax (domestic use only) data are retransmitted to SDUS stations only. The S-FAX link transmits processed satellite image data, other weather data and administrative information via S-band to domestic users in China.

Digital and cloud map transponder: Frequency: 1.7/2.0 GHz; EIRP (dBw) original cloud map and stretched cloud map: 57.5; EIRP (dBw) weather map broadcast: 46. The data rate of S-VISSR is 660 kbit/s, the modulation is: PCM/BPSK, NRZ-M, polarization: linear, bandwidth = 2 MHz. Since the signal characteristics of the S-VISSR instrument data are the same as those of the VISSR instrument of the Japanese GMS series (except the frequency), the user stations receiving GMS VISSR data are also capable of receiving S-VISSR data, simply by changing the antenna pointing and frequency of the receiver local oscillator.


 

Data Collection System (DCS) of the FY-2 Series

The DCS provides operational collection services for data collection platforms (DCPs) within its field of view. The overall system is composed of the following subsystems:

• The space segment: a DCS platform on the FY-2 satellite consisting of: a UHF/S-band transponder, a mechanically despun S-band antenna, and a UHF receive antenna. Data collection transponder:Frequency = 401/468 MHz; EIRP = 47.3 dBw; No. of channels: 133, 100 of these channels are for domestic use and 33 international channels. DCS offers a capability and a new digital S-band fax service (CCITT G3) for domestic distribution of charts and imagery.

• The deployed DCPs (Data Collection Platforms) in the ground segment. The regional DCPs are stationary DCPs installed on buoys, islands, rivers, mountains or ships.

• The ground-based NSMC (National Satellite Meteorological Center) which collects and processes the DCP data and distributes it via GTS to the user community.


 

FY-2B (FengYun-2B)

The second Chinese GEO satellite, FY-2B, was launched on June 26, 2000 from the Xichang launch center with the Long March 3 (LM-3) vehicle.

The FY-2B S/C is identical to the previous FY-2A satellite and carries the same payload (S-VISSR, and DCS). The S/C is spin-stabilized with a spin rate of 100 rpm. The on-orbit dry mass is 600 kg, the launch mass is 1250 kg. The S/C design life is 3 years. 3)

The daytime visible image can be used to derive the reflectance of cloud top and the earth surface, the nighttime infrared image can observe the thermal radiance, while the water vapor image can estimate the water vapor amount in the atmosphere. The satellite also broadcasts low resolution WEFAX image and collects data from automatic data collection platforms. Free transmission of S-VISSR data and WEFAX imagery are open to all users within the FY-2B transmission coverage.

Orbit: Geosynchronous orbit at position: 105º eastern longitude.

Channel

FY-2, A, B

FY-2, C, D, E

VIS (Visible)

0.50 - 1.05 µm

0.50 - 0.99 µm

IR1 (Infrared 1)

10.5 - 12.5 µm

10.3 - 11.3 µm

IR2

 

11.5 - 12.5 µm

IR3

 

3.5 - 4.0 µm

WV (Water Vapor)

6.3 - 7.6 µm

6.3 - 7.6 µm

Table 4: Spectral layout of the VISSR instrument beyond FY-2B


 

FY-2C (FengYun-2C)

FY-2C is a geostationary meteorological satellite of CMA (China Meteorological Administration) with the intent to replace the services of FY-2B. The FY-2C spacecraft uses dual-spin stabilization, electric power of 300 W is being provided. The S/C launch mass is 1380 kg, and the design life is 3-4 years.

While the FY-2A and -2B satellites were so-called experimental satellites in GEO, the FY-2C spacecraft is regarded as the first "operational" weather satellite in China - providing its services to a large user community.

The mission objectives of FY-2C are: 4) 5)

• Acquiring visible, infrared and water vapor cloud images

• Re-transmitting S-VISSR images and low resolution images

• Provision of data collection services

• Space environment monitoring

Like its predecessors, FY-2C is a spin-stabilized satellite. The following changes were implemented:

• The spin rate of FY-2C has been changed to 98 rpm (previously 100 rpm) to permit enough time for raw data transmission in a cycle (the transmission of a full disk image takes 25.5 minutes, rather than 25 minutes).

• The power supply of the spacecraft has been improved (from 17 Ah to 25 Ah) in support of a better eclipse management.

• The WEFAX function is being replaced by LRIT (Low Rate Information Transmission) for improved services to the user. The LRIT format is in agreement with the standard protocol recommended by CCSDS. The primary objective of the LRIT service is to deliver image data for nowcasting within a few minutes of the end of acquisition of each image

• The fax service of FY-2A, B is being discontinued on FY-2C

• FY-2C carries out two types of broadcast schedules:

- Regular schedule: provides 24 full disc images every day plus 4 images for deriving wind products

- Flood season schedule: transmits full disc images in the early half hour; for the late half hour, a certain number of sector scan images in northern hemisphere is expected to be transmitted in total size of 1400 scan lines, taking 15 minutes time to scan.

Launch: A launch of FY-2C took place on Oct. 19, 2004 on a CZ-3A vehicle from the Xichang Launch Center, China.

RF communications: Broadcast of S-VISSR data at 660 kbit/s, and LRIT (Low Rate Information Transmission) data at 150 kbit/s.

FY2_Auto0

Figure 2: Artist's view of the FY-2 satellite

Orbit: Geosynchronous orbit at position: 105º eastern longitude.

Mission status: FY-2C (launch Oct. 19, 2004) is operating nominally as of 2006. FY-2C can be regarded as the first operational meteorological satellite mission (in GEO) of China.

• The broadcast service of S-VISSR data started on January 1, 2005. From June 1, 2005 onwards, FY-2C produces and distributes also its AMV (Atmospheric Motion Vector) data products.


 

Sensor complement: (S-VISSR, DCS)

The upgraded S-VISSR (Stretched - Visible and Infrared Spin-Scan Radiometer) of FY-2C features 5 spectral bands (1 VIS, 4 IR). This measure improves the following instrument observation functions:

• The capability of detecting and calculating water vapor contents, to support semi-transparent ice cloud detecting, and to have a better accuracy of atmospheric absorption correction for better sea temperature estimation.

• Improved temperature resolution of the IR bands and SNR of the VIS band; support of split window application.

• The data quantization level of the IR bands has been increased from 256 (8 bit) to 1024 (10 bit).

Parameter / Spacecraft

FY-2A, B

FY-2C

Spectral range (µm)

0.5-1.05

0.55-0.99

FOV (µrad)

40

35

Spatial resolution (km)

1.44

1.25

Dynamic range

0-95%

0-0.98%

SNR

6.5 (2.5%)

1.5 (0.5%)

No of detectors

4+4 (spare)

4+4 (spare)

Data quantization

64 (6 bit)

64 (6 bit)

Calibration

Cold space images and solar image to realize in-orbit calibration

Table 5: Specification of the VIS band of S-VISSR

Parameter / Spacecraft

FY-2A, B

FY-2C

 

IR

WV

IR1

IR2

IR3 (WV)

IR4

Spectral range (µm)

10.5-12.5

6.3-7.6

10.3-11.3

11.5-12.5

6.3-7.6

3.5-4.0

FOV (µrad)

160

160

140

140

140

140

Spatial resolution (km)

5.76

5.76

5

5

Dynamic range

180-330 K

190-290 K

180•330 K

180-280 K

180•330 K

Temperature resolution

0.6 K

1.0 K

0.4-0.2 K

0.4-0.2 K

0.6-0.5 K

0.5-0.3 K

No of detectors

1+1
(spare)

1+1
(spare)

1+1
(spare)

1+1
(spare)

1+1
(spare)

1+1
(spare)

Data quantization

6 bit

6 bit

10 bit

10 bit

10 bit

10 bit

Calibration

Onboard blackbody calibration, once every 3 disks

The ground calibration accuracy is 1 K. Cool space and planet calibration is used for onboard calibration, once every 2 disks.

Table 6: Specification of the infrared S-VISSR channels


 

FY-2D (FengYun-2D)

The FY-2D spacecraft carries the same sensor complement as FY-2C.

Launch: A launch of FY-2D took place on Dec. 8, 2006 on a CZ-3A vehicle from the Xichang Launch Center, China.

Orbit: On the geostationary orbit, the operational configuration includes two satellites with FY-2C at 105ºE and FY-2D at 86.5ºE providing a back-up capability.


1) W. Zhang, C. Dong, J. Xu, J. Yang, "Current and Future Meteorological Satellite Program of China," CMA, Beijing, May 30, 2005, URL: http://cimss.ssec.wisc.edu/itwg/itsc/itsc14/presentations/session9/9_2_zhang.pdf

2) A. Lawler, "Blast at Xichang Derails China's Weather Effort", Space News, May 2-8, 1994, p. 3

3) http://202.106.103.181/fy2e.html

4) Report of the 31st Meeting of the Coordination Group for Meteorological Satellites (CGMS XXXI), Ascona, Switzerland, Nov. 10-13, 2003, PRC-WP-06 prepared by CMA, "Geostationary Meteorological Satellite FY-2C," http://www.eumetsat.de/en/area2/cgms/cgms_xxxi/CGMS-XXXI_Working_Papers/CGMS-XXXI_PRC_WPs/CGMS-XXXI_PRC-WP-06.pdf

5) J. Zhang, "Applications of FY-2C Meteorological Satellite in China," EUMETSAT Meteorological Satellite Conference, Dubrovnik, Croatia, Sept. 19-23,2005


This description was provided by Herbert J. Kramer from his documentation of: "Observation of the Earth and Its Environment: Survey of Missions and Sensors" - comments and corrections to this article are welcomed by the author.