Observations from Fengyun Satellites

Fengyun (FY) Satellite has a polar-orbiting series and a geostationary series. Up to now, 7 polar-orbiting (FY-1A/B/C/D and FY-3A/B/C) and 7 geostationary (FY-2A/B/C/D/E/F/G) 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 and so on.      

Fengyun Satellites: Achievements and Future

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 three-dimensional observations and quantitative application. The first of the next generation geostationary series (FY-4) is planned to launch in 2014.      

Operation and Application of A, B Satellites for Environment and Disaster Monitoring and Forecasting

Environment and disaster monitoring and forecasting small satellite constellation A and B satellites (HJ-1-A, B) are called "environment and disaster reduction satellites A and B' for short. The constellation adopts a 10:30 LT sun-synchronous circular orbit, with orbit altitude of 649 km. HJ-1-A and HJ-1-B are distributed with a phase difference of 180o in the same orbital plane, so as to enhance the time resolution of earth observation. The satellites have orbit maintenance capability, the lifetime is 3 years. Both satellites adopt CAST968 platforms. Two wide-coverage multispectral CCD cameras with resolution 30 m and width 700 km, a super-spectral imager with resolution 100 m and width 50 km as well as a data transmission subsystem of 120 Mbit/s are deployed on HJ-1-A, which also carries Ka communication testing equipment of Thailand. HJ-1-B has two wide-coverage multispectral CCD cameras (the same as satellite A), one infrared camera with resolution 150 m and width 720 km and a data transmission subsystem of 60 Mbit/s. The coverage period of the wide-coverage multispectral CCD camera is 48 hours. The revisit period of super-spectral imager is 96 hours and the coverage period of infrared camera is 96 hours.      

The United States operational polar-orbiting satellite series,TIROS-N

The U.S. launched the first of its new series of polar-orbiting, operational satellites, named TIROS-N, on 13 October 1978. The second, named NOAA-A, was launched on 27 June 1979. Together they comprise the operational system since from an average altitude of 840 km two satellites are required to provide global coverage in the equatorial zone. Operational products for FGGE (atmospheric temperature profiles, sea surface temperature analysis, and other data) are discussed and compared with prior performance. New uses in support of oceanology (Service ARGOS) are described.     

Vegetation cover mapping from NOAA/AVHRR

The visible and near infrared channels, Ch₁ and CH₂ respectively, on the Advanced Very High Resolution Radiometer (AVHRR) provide daily information for monitoring changes in vegetation and crops. Data from these channels are used to create a normalized vegetation index (NVI) that is sensitive to changes in green leaf biomass and is represented mathematically by:

$\text{NVI =}\text{CH}{}_2\text{? CH}{}_1\text{CH}{}_2\text{+ CH}{}_1$

Operational products generated at NOAA include full-scale 1-km resolution images of the NVI covering areas viewed in a single swath of the polar-orbiting NOAA satellite. Global scale NVI images are also produced by compositing over a seven-day period, saving the maximum NVI created daily for each local array (resolution of 15 km at the equator to 30 km at the poles). Such seven-day mapping reduces the effect of cloud contamination. The global vegetation indices are used by foreign and U.S. government agencies for operational and experimental purposes such as assessment of crop conditions, monitoring potential desert locust breeding grounds, forest fire danger models, and monitoring range lands for forage availability. Examples include changes in the NVI in the Lake Chad vicinity, 1981–1982 and 1984; western United States NVI; and seasonal variations of the NVI in the Sahel using the global operational data base, 1982–1983.     

Stereoscopic observations from meteorological satellites

The capability of making stereoscopic observations of clouds from meteorological satellites is a new basic analysis tool with a broad spectrum of applications. Stereoscopic observations from satellites were first made using the early vidicon tube weather satellites (e.g., Ondrejka and Conover [1]). However, the only high quality meteorological stereoscopy from low orbit has been done from Apollo and Skylab, (e.g., Shenk $\text{et al.}$ [2] and Black [3], [4]). Stereoscopy from geosynchronous satellites was proposed by Shenk [5] and Bristor and Pichel [6] in 1974 which allowed Minzner $\text{et al.}$ [7] to demonstrate the first quantitative cloud height analysis. In 1978 Bryson [8] and desJardins [9] independently developed digital processing techniques to remap stereo images which made possible precision height measurement and spectacular display of stereograms (Hasler $\text{et al.}$ [10], and Hasler [11]). In 1980 the Japanese Geosynchronous Satellite (GMS) and the U.S. GOES-West satellite were synchronized to obtain stereo over the central Pacific as described by Fujita and Dodge [12] and in this paper. Recently the authors have remapped images from a Low Earth Orbiter (LEO) to the coordinate system of a Geosynchronous Earth Orbiter (GEO) and obtained stereoscopic cloud height measurements which promise to have quality comparable to previous all GEO stereo. It has also been determined that the north-south imaging scan rate of some GEOs can be slowed or reversed. Therefore the feasibility of obtaining stereoscopic observations world wide from combinations of operational GEO and LEO satellites has been demonstrated.Stereoscopy from satellites has many advantages over infrared techniques for the observation of cloud structure because it depends only on basic geometric relationships. Digital remapping of GEO and LEO satellite images is imperative for precision stereo height measurement and high quality displays because of the curvature of the earth and the large angular separation of the two satellites. A general solution for accurate height computation depends on precise navigation of the two satellites. Validation of the geosynchronous satellite stereo using high altitude mountain lakes and vertically pointing aircraft lidar leads to a height accuracy estimate of ± 500 m for typical clouds which have been studied. Applications of the satellite stereo include: 1) cloud top and base height measurements, 2) cloud-wind height assignment, 3) vertical motion estimates for convective clouds (Mack $\text{et al.}$ [13], [14]), 4) temperature vs. height measurements when stereo is used together with infrared observations and 5) cloud emissivity measurements when stereo, infrared and temperature sounding are used together (see Szejwach $\text{et al.}$ [15]).When true satellite stereo image pairs are not available, synthetic stereo may be generated. The combination of multispectral satellite data using computer produced stereo image pairs is a dramatic example of synthetic stereoscopic display. The classic case uses the combination of infrared and visible data as first demonstrated by Pichel $\text{et al.}$ [16]. Hasler $\text{et at.}$ [17], Mosher and Young [18] and Lorenz [19], have expanded this concept to display many channels of data from various radiometers as well as real and simulated data fields.A future system of stereoscopic satellites would be comprised of both low orbiters (as suggested by Lorenz and Schmidt [20], [19]) and a global system of geosynchronous satellites. The low earth orbiters would provide stereo coverage day and night and include the poles. An optimum global system of stereoscopic geosynchronous satellites would require international standarization of scan rate and direction, and scan times (synchronization) and resolution of at least 1 km in all imaging channels. A stereoscopic satellite system as suggested here would make an extremely important contribution to the understanding and prediction of the atmosphere.     

静止气象卫星的功能及姿态稳定方式对功能的影响

<正> 一、前言国际电信联盟无线电规则把气象卫星业务定义为用于气象目的的地球探测卫星业务。但对静止气象卫星业务来说,气象业务部门希望它不仅要具有气象观测功能,而且要具有收集、传送和分发各种气象信息的功能。因此,静止气象卫星不仅是位于静止轨道上的空间气象观测平台,而且也是收集,传送和分发气象数据的中继站,其有效载荷主要是观测地球大气的各种遥感仪器及收集、传送和分发气象数据的通信系统。它兼有地球探测卫星和通信卫星的     

FY-3 Meteorological Satellites and the Applications

FY-3 is the second generation polar-orbiting meteorological satellite of China. The first satellite named FY-3A of this series was launched on 27 May 2008. The first operational satellite named FY-3C of this series was launched on 23 September, 2013. The new generation satellites are to provide three-dimensional, quantitative, multi-spectral global remote sensing data under all weather conditions, which will greatly help the operational numerical weather prediction, global climate change research, climate diagnostics and prediction, and natural disaster monitoring. They will also provide help for many other fields such as agriculture, forestry, oceanography and hydrology. With the abovementioned capability, the FY-3 satellites can make valuable contributions to improving weather forecasts, global natural-disaster and environmental monitoring.      

The use of stereoscopic satellite observation in the determination of the emissivity of cirrus

The feasibility of determining cirrus “emissivity” from combined stereoscopic and infrared satellite observations in conjunction with radiosounding data is investigated for a particular case study. Simultaneous visible images obtained during SESAME-1979 from two geosynchronous GOES meteorological satellites were processed on the NASA/Goddard interactive system (AOIPS) and were used to determine the stereo cloud top height Z_C as described by Hasler [1]. Iso-contours of radiances were outlined on the corresponding infrared image. Total brightness temperature T_B and ground surface brightness temperature T_S were inferred from the radiances. The special SESAME network of radiosoundings was used to determine the cloud top temperature T_CLD at the level defined by Z_C. The “effective cirrus emissivity” NE where N is the fractional cirrus cloudiness and E is the emissivity in a GOES infrared picture element of about 10 km × 10 km is then computed from T_B, T_S and T_CLD.     

基于偏心率和倾角矢量的双星隔离策略

针对中国地球静止轨道双星共位的需要, 研究了双星共位的工程实现问题, 提出了一种使用偏心率矢量和倾角矢量联合隔离实现双星共位的方法. 给出了基于偏心率矢量和倾角矢量联合隔离的基本方法、约束方程和工程实现的控制策略, 并通过模拟计算和工程实际应用情况, 验证了该方法的正确性.      

Geostationary operational environmental satellite system performance

The United States supported the First GARP Global Experiment (FGGE) by the use of three geostationary satellites: GOES-East, located at 75°W longitude, GOES-West at 135°W longitude, and, through a special cooperative effort by the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, and the European Space Agency, GOES-Indian Ocean at 58°E longitude. During the FGGE Operational Year, the GOES-East coverage was provided, in turn, by GOES-2, SMS-1, and SMS-2. The GOES-West coverage was provided by GOES-3, and GOES-1 served at the GOES-Indian Ocean location. Satellite and instrument performance was generally satisfactory during that period except for the loss of infrared data from the Indian Ocean GOES for an aggregate of 31 days due to intermittent operation of the sensor. From the GOES-East and GOES-West data, the National Environmental Satellite Service produced cloud motion vectors for 0000, 1200, and 1800 GMT daily, numbering in total about 1400 vectors per day. High resolution wind vectors at the rate of somewhat under 3000 daily were derived from the data from all three satellites in the tropical zone bounded by 15°N and 15°S latitude by the University of Wisconsin. In addition to their contributions to the FGGE research data sets, these three satellites provided other real-time benefits and services.     

基于FY-3C掩星数据偶发E层的研究

利用FY-3C极轨卫星提供的2014年6月至2015年5月的GPS无线电掩星数据,统计分析了全球范围内抽样频率为50 Hz的C/A码SNR扰动情况,进而对偶发E层进行了研究.结果表明:偶发E层在夏季半球中纬地区的扰动强度远远大于冬季半球同一纬度地区的扰动强度,偶发E层在纬度40°附近扰动明显增强;在E层100 km高度附近,Es层在10:00 LT和22:00 LT达到峰值;Es层在夏季半球的出现率明显高于冬季半球;FY-3C卫星的掩星观测结果与COSMIC系统的观测结果较一致,可以利用FY-3C卫星的掩星数据研究电离层偶发E层等的变化.      

The earth radiation budget experiment: Early validation results

The Earth Radiation Budget Experiment (ERBE) consists of radiometers on a dedicated spacecraft in a 57° inclination orbit, which has a precessional period of 2 months, and on two NOAA operational meteorological spacecraft in near polar orbits. The radiometers include scanning narrow field-of-view (FOV) and nadir-looking wide and medium FOV radiometers covering the ranges 0.2 to 5 μm and 5 to 50 μm and a solar monitoring channel. This paper describes the validation procedures and preliminary results. Each of the radiometer channels underwent extensive ground calibration, and the instrument packages include in-flight calibration facilities which, to date, show negligible changes of the instruments in orbit, except for gradual degradation of the suprasil dome of the shortwave wide FOV (about 4% per year). Measurements of the solar constant by the solar monitors, wide FOV, and medium FOV radiometers of two spacecraft agree to a fraction of a percent. Intercomparisons of the wide and medium FOV radiometers with the scanning radiometers show agreement of 1 to 4%. The multiple ERBE satellites are acquiring the first global measurements of regional scale diurnal variations in the Earth's radiation budget. These diurnal variations are verified by comparison with high temporal resolution geostationary satellite data.     

The role of space techniques in FGGE

The space-based sub-system of the composite observing system, operated during the Operational Year of the Global Weather Experiment, played an indispensable role in the acquisition of data and in transmitting data from surface-based and airborne observational platforms to data-processing centres. The sub-system comprised both geostationary and near-polar orbiting meteorological satellites and special efforts were undertaken to keep the performance of the system as close as possible to that which had been anticipated during the planning stage of the Experiment.Five geostationary satellites were spaced at approximately uniform intervals around the equator. They were used primarily to derive wind vectors by measuring the displacement of clouds. The satellites also provided communication support for the Aircraft to Satellite Data Relay system, by which flight level meteorological data were automatically transmitted to ground receiving stations.Three polar orbiting satellites provided data simultaneously during the whole Operational Year. Vertical temperature soundings, clear-radiance data, sea-surface temperature and wind speed data, and total atmospheric water vapour data were produced for inclusion in the research data set of the Experiment. Two of these satellites /TIROS-N and NOAA-6/ carried a new data collection and platform location system, a basic component of the Tropical Constant Level Balloon System and the Drifting Buoy System of FGGE.     

Recent Progress of Fengyun Meteorology Satellites

After nearly 50 years of development, Fengyun (FY) satellite ushered in its best moment. China has become one of the three countries or units in the world (China, USA, and EU) that maintain both polar orbit and geostationary orbit satellites operationally. Up to now, there are 17 Fengyun (FY) satellites that have been launched successfully since 1988. There are two FY polar orbital satellites and four FY geostationary orbit satellites operate in the space to provide a huge amount of the earth observation data to the user communities. The FY satellite data has been applied not only in the meteorological but also in agriculture, hydraulic engineering, environmental, education, scientific research and other fields. More recently, three meteorological satellites have been launched within the past two years. They are FY-4A on 11 December 2016, FY-3D on 15 November 2017 and FY-2H on 5 June 2018. This paper introduces the current status of FY meteorological satellites and data service. The updates of the latest three satellites have been addressed. The characteristics of their payloads on-boarding have been specified in details and the benefit fields have been anticipated separately.      

International co-operation in the use of satellites for the world climate programme

The World Climate Programme (WCP), in dealing with the complex topic of climate, is highly dependent on observations and measurements of many parameters and phenomena occurring from the surface of the Earth to the top of the atmosphere, and global in extent. Satellite observations and measurements are therefore critical to the success of many different components in the WCP. The present network of polar-orbiting and geostationary satellites represents nearly 25 years of international co-operation and now constitutes a part of the Global Observing System of the World Weather Watch. The WCP can satisfy a number of its observation and measurement requirements by making use of this existing satellite network. This can be done either through use of the operational products produced for near-real time applications or through use of the satellite data stored in the archives. An awareness of how to interact with the sources, combined with knowledge about the limitations and deficiencies of satellite data and products, are critical for scientists working in climate research and applications. Among the most important characteristics of satellite observations and measurements for the WCP are the global coverage, consistency and continuity of the data sets.     

静止气象卫星系统中的一项关键电子技术——图象信号的同步缓冲

在静止气象卫星系统中,从可见光与红外自旋一扫描辐射计(V1SSR)获得的原始数据首先要进行同步和缓冲,才能送向数据处理中心(DPC)。同步是为了恢复出象点有准确位置的好的图象,并可用来准确测量风速(一项重要的应用);而缓冲是为了数据传输和输入计算机的方便。从正确使用数据的观点看,同步和缓冲是系统中不可缺少的技术。本文介绍Meteosat和GMS两个气象卫星系统中被成功地应用着的同步和缓冲系统(S/DB),并对它们的性能和精度进行了分析。     

The possible applications of Meteosat for monitoring the rain season in the Sahel zone: The case of Senegal

The use of geostationary meteorological satellites for monitoring climate is relatively well known. However, the application of satellite data for agronomical purposes is still far form being operational. Recent work shows the possibility of establishing statistical models adapted to each region which can predict rain to within a time interval of 12 to 24 hours, based on the analysis of cloud cover. In the same way, thermal IR images may be used, employing the quasi-linear relationship between surface temperature and real evapotranspiration E.T.R. This is the objective of the project on monitoring the hydric balance in Senegal, associating INRA-IRAT and LERTS in France, ISRA and Meteorologie Nationale in Senegal. The first results obtained by Assad et al from two Meteosat images taken during 1979 establishing an inverse relationship between surface temperature and rain, over the total area of Senegal, were maintained for 16 images taken during the 1984 and 1985 rain period. Their analyses show that it is possible : - To identify the most favorable sowing periods, - to diagnose periods of high climatic risk for crops, and to cartograph rain distribution from spatial variations in surface temperature.     

Collision probability and spacecraft disposition in the geostationary orbit

Since 1963 approximately 300 satellites have been launched into the geostationary orbit, followed possibly by another additional 200 satellites up to the year 2000. Ground surveillance with radar and optical sensors able to detect objects of 1 m minimum size in the geostationary ring indicates a total population of several hundred which includes active and defunct satellites and spent upper stages. In addition, a population of untrackable objects is conjectured, whose size can only be estimated, possibly several thousand of smaller objects.

The purpose of this paper is to review the long-term evolution of orbits in the geostationary ring and at higher altitude, the collision probabilities and disposition options.

The major perturbations are considered including attitude-orbit cross-coupling effects which could cause secular orbit perturbations.

Collision probabilities for current and projected populations are reviewed considering different approaches, such as a deterministic treatment of the uncontrolled population and a stochastic modeling for the controlled satellites. Also, colocation, that is sharing of the same longitude slot by several operational satellites, is a potential source for collision, if no preventive measures are taken.

As regards spacecraft disposition options, the conclusion is that reorbiting is currently the only practical measure to safeguard the geostationary orbit. In this recommended procedure the defunct satellites are inserted into a so-called graveyard orbit, located suffieciently high above the geostationary orbit.     

Assessment of the consequences of the Fengyun-1C breakup in low Earth orbit

On 11 January 2007, the People’s Republic of China conducted a successful anti-satellite test against one of their defunct polar-orbiting weather satellites. The target satellite, called Fengyun-1C, had a mass of 880 kg and was orbiting at an altitude of about 863 km when the collision occurred. Struck by a direct-ascent interceptor at a speed of 9.36 km/s, the satellite disintegrated, spreading the cataloged fragments between 200 and 4000 km, with the highest concentration near the breakup height. By the end of April 2008, 2377 pieces of debris, including the original payload remnant, had officially been cataloged by the US Space Surveillance Network. Of these, nearly 1% had reentered the Earth’s atmosphere. This deliberate act is the largest debris-generating event on record, and its consequences will adversely affect circumterrestrial space for many years.