0254-6124/2010/30(5)-468 06 Chin. J. Space Sci. Wang Jingsong, Zhang Jiashen, Tang Yunqiu. Fengyun satellites: achievements and future. Chinese Journal of Space Science, 2010, 30(5): 468-473 Fengyun Satellites: Achievements and Future Wang Jingsong Zhang Jiashen Tang Yunqiu (National Satellite Meteorological Center/National Center for Space Weather, China Meteorological Administration, Beijing 100081) Abstract Chinese meteorological satellite, Fengyun (FY) Satellite, has a polar-orbiting series and a geostationary series. Up to now, 5 polar-orbiting (FY-1A/B/C/D and FY-3A) and 5 geostationary (FY-2A/B/C/D/E) satellites were launched. FY data has been being intensively applied not only to meteorological monitoring and prediction but also to many other fields regarding ecology, environment, disaster, space weather and so and. The FY data sharing system, FengyunCast, is now one of the three components of global meteorological satellite information dissemination system, GEONETCast. The first satellite of the new generation polar-orbiting series, FY-3A, was launched on 27 May, 2008, demonstrating the FY polar-orbiting satellite and its application completed a great leap to realize threedimensional observations and quantitative application. The first of the next generation geostationary series (FY-4) is planned to launch in 2014. Keywords FY satellite, Polar-orbiting satellite, Geostationary satellite, Remote sense, Space weather 1 A Brief Overview of FY Satellites China initiated its meteorological satellite development programme in 1970. Since then, China has launched Fengyun (FY) series, i.e. FY-1, FY-2 and FY-3 meteorological satellites, which were developed independently with Chinese efforts and put into operational uses respectively, established an operational Earth observation system composed of both polar orbiting and geostationary meteorological satellites. These satellites are named with a sequence of odd numbers for polar series, e.g. FY-1, FY-3, while the geostationary satellites follow a sequence of even numbers (e.g. FY-2, FY-4) [1]. 1.1 Polar Series: FY-1 and FY-3 The first Chinese polar-orbiting meteorological satellite FY-1 was put into the National Plan in 1977. The ground system of the satellite, which was designed to be compatible with those for NOAA satellites in data reception and processing, began its construction in 1978 and the project was completed in 1987. On September 7, 1988, the first FY-1 satellite was launched, which was known as FY-1A. So far, four satellites of FY-1 series were launched successfully. Currently, FY-1D, launched on May 15, 2002 is still in operation. FY-3 is the second generation of China s polar orbiting meteorological satellite. This series includes 8 satellites, namely FY-3A/B/C/D/E/F/G/H, for the duration 2007 2020. The first two satellites FY-3A and FY-3B are experimental, and FY- 3C/D/E/F/G/H are operational. They will alternately take morning orbit or afternoon orbit. The first satellite in FY-3 series, i.e. FY-3A, was launched on May 27, 2008. The missions of FY-3 are listed as follows: To provide global 3-dimensional atmospheric thermal and moisture structures, cloud and precipitation parameters, in order to support global numerical weather prediction. To provide global imagery for monitoring large-scale meteorological and hydrological disasters as well as biosphere and environment anomalies (see Figure 1). To derive geophysical parameters to support research activities in global and regional climate change. Received April 25, 2010 E-mail:wangjs@cma.gov.cn
Wang Jingsong et al.: Fengyun Satellites: Achievements and Future 469 Figure 1 Global Mosaic from Medium Resolution Spectral Imager (MERSI) of FY-3A (July 19, 2008). 1.2 Geostationary Meteorological Satellites In 1986, China s first geostationary meteorological satellite FY-2 was officially incorporated into the national plan. The construction of its ground systems was started in 1988, and completed in 1994. FY-2A was successfully launched on 10 June, 1997. According to the development plan for geostationary meteorological satellite, China s first-generation geostationary meteorological satellites are divided into 3 batches. The first batch includes two experimental satellites FY-2A and FY-2B. The second batch includes operational satellites FY-2C (see Figure 2), FY-2D and FY-2E. FY-2D and FY-2E, lunched on 8 December, 2006 and 23 December, 2008, respectively, are currently operating in orbit and provide application services. The third batch is expected to include FY-2F, FY-2G and FY-2H, and their performances will be appropriately improved based on the second batch, to ensure the continuous and stable transition between different batches. 2 FY-series Payloads and Their Observing Capabilities 2.1 Polar-orbiting Meteorological Satellites 2.1.1 FY-1 Meteorological Satellites The FY-1 satellites were designed to operate in sun- synchronous orbits, and their main remote sensing instruments were multi-channel visible and infrared scanning radiometers. FY-1 satellites were the first applicationoriented Earth observing satellite series developed and launched by China. A wide range of key technical issues were solved including the launch and precise entry into expected sun-synchronous orbits, long-life satellite platform with three-axis stabilization, high-quality visible and infrared scanning radiometers, the storage and playback of global data on satellites, monitoring, control and management of long-term satellite operations, construction of surface data receiving and processing system, and long-term operation of satellite systems. 2.1.2 FY-3 Meteorological Satellites As China s second-generation polar-orbiting meteorological satellites, FY-3 features the following advances (see Figure 3). Solar panels automatically orient themselves to the Sun to enhance the power supply systems on board the satellites. 3 channels for data transmission (one S-band and two L-bands) are used to meet the needs of a variety of payloads to transmit and acquire global data. FY-3 (Batch-01) carries a total of 11 instruments including Visible & InfraRed Radiometer (VIRR), InfraRed Atmospheric Sounder (IRAS), MicroWave Temperature Sounder (MWTS), MicroWave Humidity Sounder (MWHS), MEdium Resolution Spectral Imager (MERSI), Solar Backscatter Ultraviolet Sounder (SBUS), Total Ozone Unit (TOU), MicroWave Radiation Imager (MWRI), Solar Irradiation Monitor (SIM), Figure 2 First image from visible channel of FY-2C (October 29, 2004). Figure 3 Payloads of FY-3A.
470 Chin. J. Space Sci. 2010, 30(5) Earth Radiation Measurement (ERM), and Space Environment Monitor (SEM). Several of these instruments will provide vital information on atmospheric temperature and water vapor profiles that can be assimilated directly into numerical weather prediction models. 2.2 Geostationary Meteorological Satellites FY-2 satellites are spin-stabilized, and they observe the Earth along the synchronous orbits from about 35 800 km above the equator. The major instruments of FY-2 satellites include a multi-channel scanning radiometer and a space environment monitor, and the latter has 2 components: one for solar X-ray monitoring and the other for space particle monitoring. A multi-channel scanning radiometer is used for Earth observations to acquire daytime visible images, daytime and nighttime infrared images, water vapor pictures and relevant meteorological parameters. A transponder is used to transmit raw images, high resolution stretched digital images and low-resolution images to ground stations for national and international users. Observational data from the data collection platforms operated by meteorological, hydrological and oceanographic authorities are collected and retransmitted. A space environment monitor is used to monitor space environment along the orbit of the satellite to provide observations for satellite engineering and space environment monitoring. 3 Applications of FY Satellite Observations Accompanying the development of FY satellites, the comprehensive capability of satellite data application in China also acquires fruitful achievements. 3.1 Applications in Services for Aerospace Missions The energetic particle detectors onboard the FY-1 and FY-3 satellites mainly monitor the high-energy charged particles (heavy ions, protons, electrons) in orbital space, providing services for satellite missions and engineering designs. Such information is mainly used to warn of severe disturbance along the orbit, provide a background of high-energy particle radiation at the altitude of the orbit (see Figure 4), evaluate satellites anti-irradiation capability and analyze abnormal conditions, and contribute to engineering designs for subsequent satellites. The space environment detector onboard the FY-2 is used to monitor solar activity and charged particle radiation, to forecast, warn of and nowcast solar flares and proton events, provide support to ensure the safety of inorbit satellites. The observations help the improvement of the service capability for aerospace missions. For example, the data from FY-1D was used, among others, to support the launching and in-orbit operation of FY-3A, while the FY-3A data then played an important role in the launch and orbiting of the Shenzhou-6 spacecraft. 3.2 Extensive Applications of Satellite Data to Weather Forecast A study was started at least 30 years ago in China to apply satellite data in weather forecast. Based on a conceptual model that was developed for weather forecast with satellite cloud image data, analysis of cloud structures and weather systems was performed with visible and infrared data received from foreign satellites. More and more satellite products, involving atmospheric profiles, cloud track wind and quan- Figure 4 Global distribution of energetic particles obtained by FY-3A.
Wang Jingsong et al.: Fengyun Satellites: Achievements and Future 471 titative precipitation estimates, etc., were generated with development of remote sensing technologies and satellite sensors, such as TOVS, ATOVS and AVHRR. To provide a new-generation quantitative, diagnostic model for satellite weather analysis, it is very important to carry out more studies on weather diagnostic analysis with satellite products. To directly assimilate ATOVS radiance data from various NOAA satellites in a Global Forecasting System (GFS), a 3DVAR data assimilation system (GRAPES 3DVAR) has been set up in CMA. Batch tests show that assimilation of ATOVS data has contributed significantly to improving forecasting skill in global medium-range NWP and to extend efficient predicted time. To use ATOVS radiance data in its operational GFS that is developed from T213/T639, a 3D-VAR assimilation system (SSI, GSI) from NCEP has been introduced in National Meteorological CenterbeforeGRAPESGFSisinoperation. Itshows, from a 8-months quasi-operational experiment, that the efficient global medium-range NWP prediction has been extended at least half a day while ATOVS data are assimilated in the system. 3.3 Applications to Climate and Climate Change Though application of satellite data to studies on climate and climate change witnesses rapid development, although it started late. Currently, the sea surface temperature data derived from satellites, Surface Solar Irradiance data, Precipitation Estimation, Total Precipitable Water Cloud Classification, snow features and trends of changes in cover and sea ice data have been used for monitoring and analyzing global sea surface temperature, ENSO, monsoons, as well as snow cover in the North Hemisphere, and sea ice in both Arctic and Antarctic (see Figure 5). Figure 5 Composite imagery of Antarctic by FY-1C GDPT. 3.4 Applications to Agro-ecological Hazards Monitoring In monitoring agro-ecological conditions, satellite data have been used with a solid work, and have played an important role in monitoring and assessing the hazards and disasters, which are induced by typhoons, rainstorms, floods, cold waves, heavy fog, ice & snow, frost, inundation due to ice jam, heat waves, droughts, sand & dust storms, forest and grassland fires, geological disasters, etc. (for instance, Figure 6). In agriculture applications using satellite data, quite early China began to monitor crop growth dynamically and to estimate crop yields by using vegetation index and drought index, and these work are well founded. Subsequently, combining with such satellite products as Fraction of Photosynthetic Active Radiation (FPAR), Land Surface Temperature (LST), cloud coverage and water body index, China has built up its capacity in making refined climatic resource surveys, and in monitoring and assessing land use change and desertification. In application to environment monitoring, with multi-channel information (including visible and infrared) derived from satellite data, preliminary research and service have been made on urban heat island effects, atmospheric smog and dust, algal blooms, forest pests and diseases, which are related to air, water, mineral pollutions and vegetation destruction. This has paved a way for making further environment monitoring and assessing. 3.5 Data and Products Services It s is very important to establish safer and more efficiency satellite data service in modern science research activities especially in weather forecasting in order to save more lives in disasters and create a more harmonious world. Many data and products services have been built in FY satellite s ground systems in the last 30 years. FengyunCast, one of worldwide information dissemination system by which satellite and in situ data, products and services are transmitted to users through communications satellites, is primarily used for the distribution of images and derived products from China s FY series satellites to both domestic and international users (see Figure 7). It also provides access to data and services provided by external data providers. FY Data Service Center is one
472 Chin. J. Space Sci. 2010, 30(5) Figure 6 Some examples of FY applications: (a) drought, (b) sea ice, (c) fog, (d) dust storm, (e) Antarctic ozone hole and (f) space weather. Figure 7 Global information dissemination system (GEONETCast) Coverage. of departments in NSMC which is in charge of data archiving, sharing and management. The data service web site (http://fy3.satellite.cma.gov.cn/arssen/) is built to provide meteorological satellites data and products on line service and to make a contribution to the research of saving people s life, atmosphere science, climate change and other relevant scientific areas. There are several datasets been derived from more than 10 satellites, including FY satellites, NOAA satellites, some other meteorological satellites, and EOS satellites in this website. Also, there are several datasets achieved by NSMC from 1980s until
Wang Jingsong et al.: Fengyun Satellites: Achievements and Future 473 Figure 8 Tentative plan for FY satellites in the next decade. present. User can get data files which they need in their research by using the data search tool conveniently and download data files via FTP server. The website becomes the most effective and common system providing FY satellite data and products. 4 Future Development Plan Development plan for Chinese meteorological satellite in future are as follows (see Figure 8) [2] : By 2012, China will establish an integrated operational Earth observing system with multiple satellites including FY-2 and FY-3, to enhance data quality and applications to weather analysis, NWP prediction and environment monitoring. By 2020, an integrated operational Earth observing system composing both high- and low-orbit satellites represented by FY-3 and FY-4 series of satellites will be established, the continuous, stable and reliable data of the 5 components of the Earth s climate system (atmosphere, hydrosphere, biosphere, cryosphere and lithosphere) and their interactions will be achieved. The temporal, spatial, spectral resolutions and accuracy of radiometric measurements by satellites will be significantly improved, and observing capabilities for medium- and small-scale weather and the Earth s environment will be considerably enhanced; quantitative satellite data and products will be extensively used in weather prediction, Earth s environment monitoring and prediction for operational and scientific purposes at all levels. The operational FY-3 polar-orbiting satellite (Batch-02) series will include both morning and afternoon orbiters. At the same time, low-inclination precipitation measurement radars on board will be developed, which will support a new Earth observation network of 3-satellite constellation. The second-generation geostationary meteorological satellites (FY-4) will include optical and microwave sounders, which will adopt the 3-axis stabilization, being capable to detect surface features, 3-D distribution of atmospheric temperature and humidity, lightning and space weather events, etc. The space environment observing capabilities will be greatly enhanced. On board FY-4, new payloads for solar observation are proposed such as solar X-rays and extreme ultraviolet imager and solar X-ray and EUV radiometer. Based on FY-3 platforms, near-earth space environment, especially of ionosphere and aurora will be monitored on operational basis. As the only Chinese operational satellite series, FY has been playing more and more important role in weather, climate, space weather, environment and disaster monitoring. As Premier Wen Jiabao pointed out: Without FY Satellites, we would not be able to make accurate, timely and efficient weather forecasts or obtain scientific data regarding climate change. It is important to accelerate the development of our meteorological satellites. References [1] Dong Chaohua et al. Thirty Years of Fengyun Satellites, National Satellite Meteorological Center [R]. 2001, Beijing [2] China Meteorological Administration. Long-Term Plan for Fengyun Meteorological Satellites [R]. 2010, Beijing