GF-1 (Gaofen-1) High-resolution Imaging Satellite / CHEOS series
Gaofen-1 (gao fen = high resolution) is the first of a series of high-resolution optical Earth observation satellites of CNSA (China National Space Administration), Beijing, China. The civilian HDEOS (High-Definition Earth Observation Satellite) program was proposed in 2006, it received government approval and was initiated in 2010. China plans to launch six HDEOS spacecraft between 2013 and 2016. 1)
The main goal of the HDEOS series is to provide NRT (Near-Real-Time) observations for disaster prevention and relief, climate change monitoring, geographical mapping, environment and resource surveying, as well as for precision agriculture support. The major users of the observation data will be the Ministry of Land and Resources, Ministry of Environmental Protection, and the Ministry of Agriculture.
In 2010, the Chinese government approved to implement CHEOS (China High-resolution Earth Observation System), which is an extension of the HDEOS program. The CHEOS series will consist of seven optical/microwave satellites. 2)
China's push into high-resolution optical Earth observation through its seven-satellite CHEOS system is slightly delayed but will see the launch of a second satellite in 2014 and three more satellites by 2016, according to CNSA (China National Space Administration). 3)
The implementation plan of CEOS satellite series is as follows:
• Construction period: 2010-2020
• The second satellite (GF-2) will be launched in 2014 and be put into service.
• By 2016, the next three satellites will be launched.
• By 2020, the entire CHEOS series of satellites will be on orbit.
Figure 1: Illustration of the deployed GF-1 spacecraft (image credit: CAST)
Gaofen 1 is based on the CAST small satellite bus designed and built by China SpaceSat Co. Ltd. (also referred to as DFH Satellite Co. Ltd.), the commercial subsidiary of CAST (Chinese Academy of Space Technology). The satellite is equipped with a pair of solar panel wings, each with three solar panels. The CAST-2000 bus is a small platform with high performance, expandability and flexibility. The CAST-2000 bus is of HJ (Huan Jing)-1A and -1B mission heritage, both spacecraft were launched in Sept. 2008.
ADCS (Attitude Determination and Control Subsystem): The spacecraft is 3-axis stabilized; it has the capabilities of highly precise control, large-range sway maneuver, flexible orbit maneuver, highly integrated housekeeping and highly effective power supply.
RF communications: the spacecraft features an S-band TT&C subsystem, an X-band data transmission subsystem.
The Gaofen-1 spacecraft has a launch mass of 1266 kg. The design life is 5 years. 4)
Figure 2: Photo of the Gaofen-1 spacecraft during AIT (image credit: )
Launch: The GF-1 spacecraft was launched on April 26, 2013 on a CZ-2D (Long March -2D) vehicle from the JSLC (Jiuquan Satellite Launch Center) in northwest China. The GF-1 spacecraft is the first demonstration mission of the CHEOS program (Ref. 2). 5) 6)
Orbit: Sun-synchronous orbit, altitude ~650 km, inclination = 98º, LTAN (Local Time on Ascending Node) = 10:30 hours.
The secondary payloads were:
• TurkSat-3USat, a nanosatellite (3U CubeSat, ~ 4 kg) of ITU (Istanbul Technical University), Istanbul, Turkey.
• NEE-01 Pegasus, a CubeSat of EXA (Ecuadorian Civilian Space Agency), Ecuador.
• CubeBug-1 of INVAP, a 2U CubeSat of Argentina, sponsored by the Argentinian Ministry of Science, Technology and Productive Innovation, INVAP S.E., Satellogic SA, and Radio Club Bariloche.
• Feb. 2014: The Gaofen-1 spacecraft and its payload are operating nominally. The in-orbit test demonstrates that the performance of GF-1 meets the design requirements completely (Ref. 3).
• December 2013: Gaofen-1, China's high-definition Earth observation satellite, has been formally put into service, as reported by SASTIND (State Administration of Science, Technology and Industry for National Defense). 7) 8) 9)
- The satellite has undergone eight months of in-orbit tests since it blasted off on April 26. It has met requirements and even performed better than expected by sending back high quality imagery, according to SASTIND.
- Thus far, the satellite has provided data on the Lushan earthquake in Sichuan, floods in northeastern China and the smog in northern and eastern China during the test period. It also provided Pakistan with images after an earthquake in the country on September 24, 2013.
• On June 6, 2013, SASTIND released the first 13 photos from the high-resolution earth observation satellite Gaofen-1. The images feature four cities, including Beijing, Shanghai, Yinchuan and Datong. 10)
Figure 3: On May 21, 2013, the WFI instrument of Gaofen-1 acquired this 16 m MS image of the Yellow River delta region in China (image credit: CNSA)
Figure 4: Extract of Figure 5 of the PMC with 2 m Pan/ 8 m MS fusion data acquired on May 1, 2013 showing the Beijing District in China (image credit: CNSA)
Figure 5: First high-resolution image of Beijing acquired by Gaofen-1 (image credit: SASTIND)
• On April 28, 2013, the RADI Miyun Ground Station succeeded in receiving the first track of image data from the Gaofen-1 spacecraft. 11)
Sensor complement: (PMC, WFI)
The satellite carries two 2 m panchromatic and 8 m multispectral high-definition cameras, and four 16 m resolution wide-angle cameras.
PMC (PAN and Multispectral Camera)
PMC is a high-resolution pushbroom imager (2 cameras) with TDI (Time Delay Integration) capability observing in the visible range at a resolution of 2 m in PAN, and of 8 m in MS (Multispectral)mode.
Table 1: Parameters of the PMC instrument
WFI (Wide Field Imager)
WFI is a medium-resolution pushbroom camera set (4 cameras) with TDI (Time Delay Integration) capability observing in the VNIR range at a spatial resolution of 16 m in MS mode.
Table 2: Parameters of the WFI instrumentation
1) “China launches Gaofen-1 satellite,” Xinhua, April 26, 2013, URL: http://www.china.org.cn/china/2013-04/26/content_28668480.htm
2) H. Qi, “China High-resolution Earth Observation System (CHEOS) and its Latest Development,” Proceedings of the 51st Session of Scientific & Technical Subcommittee of UNCOPUOS, Vienna, Austria, Feb. 11-22, 2014, URL: http://www.unoosa.org/pdf/pres/stsc2014/tech-47E.pdf
3) Peter B. de Selding, “China Pushing Ahead on Hi-Res Satellite System,” Space News, Feb. 28, 2014, URL: http://spacenews.com/article/civil-space/39665china-pushing-ahead-on-hi-res-satellite-system
4) Rui C. Barbosa, “China back in action with Long March 2D launch of Gaofen-1,” NASA Spaceflight.com, April 25, 2013, URL: http://www.nasaspaceflight.com/2013/04/china-back-in-action-long-march-2d-gaofen-1/
5) Stephen Clark, “Four satellites launched on China's Long March rocket,” Spaceflight Now, April 26, 2013, URL: http://www.spaceflightnow.com/news/n1304/26longmarch/#.UXuGc0okS2o
6) Patrick Blau, “Long March 2D performs China's first Orbital Launch of 2013,” Spaceflight 101, April 26, 2013, URL: http://www.spaceflight101.com/long-march-2d-gaofen-1-launch.html
7) “China's HD observation satellite opens its eyes,” Space Daily, Dec. 31, 2013, URL: http://www.spacedaily.com/reports/Chinas_HD_observation_satellite_opens_its_eyes_999.html
8) “Gaofen-1 satellite goes into service,” Xinhua, Dec. 31, 2013, URL: http://www.shanghaidaily.com/national/Gaofen1-satellite-goes-into-service/shdaily.shtml
9) “China's HD Earth Observation Satellite Put into Use,” CRIEnglish.com, Dec. 30, 2013, URL: http://english.cri.cn/6909/2013/12/30/2743s805813.htm
10) “China publicizes Earth observation satellite's HD photos,” Xinhua, June 6, 2013, URL: http://www.china.org.cn/china/Off_the_Wire/2013-06/06/content_29045699.htm
11) “Reception of the First Image Data from Gaofen-1,” Institute of Remote sensing and Digital Earth (RADI), URL: http://english.radi.cas.cn/Research/RP/201307/t20130717_106431.html
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.