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     

气象卫星的现况和发展

<正> 一、引言自从1960年发射第一颗气象卫星以来已经25年了。这25年来气象卫星技术及其应用都有了很大发展,在全球天气预报、灾害性天气监视、海洋和水文环境监测、农业和交通中起了越来越重要的作用。气象卫星的功能可以大致概括为: (一)利用遥感探测仪器对卫星下垫面进行探测。探测器主要有两类:一类是成象仪     

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.      

Update on Fengyun Meteorological Satellite Program and Development

China began to develop its meteorological satellite program since 1969. With 50-years' growing, there are 17 Fengyun (FY) meteorological satellites launched successfully. At present, seven of them are in orbit to provide the operational service, including three polar orbiting meteorological satellites and four geostationary meteorological satellites. Since last COSPAR report, no new Fengyun satellite has been launched. The information of the on-orbit FY-2 series, FY-3 series, and FY-4 series has been updated. FY-3D and FY-2H satellites accomplished the commission test and transitioned into operation in 2018. FY-2E satellite completed its service to decommission in 2019. The web-based users and Direct Broadcasting (DB) users keep growing worldwide to require the Fengyun satellite data and products. A new Mobile Application Service has been launched to Fengyun users based on the cloud technology in 2018. In this report, the international and regional co-operations to facilitate the Fengyun user community have been addressed especially. To strengthen the data service in the Belt and Road countries, the Emergency Support Mechanism of Fengyun satellite (FY_ESM) has been established since 2018. Meanwhile, a Recalibrating 30-years' archived Fengyun satellite data project has been founded since 2018. This project targets to generate the Fundamental Climate Data Record (FCDR) as a space agency response to the Global Climate Observation System (GCOS). At last, the future Fengyun program up to 2025 has been introduced as well.      

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.      

Orbit determination of BDS-3 satellite based on regional ground tracking station and inter-satellite link observations

The BeiDou global navigation satellite system (BDS-3) has established the Ka-band inter-satellite link (ISL) to realize a two-way ranging function between satellites, which provides a new observation technology for the orbit determination of BDS-3 satellites. Therefore, this study presents a BDS satellite orbit determination model based on ground tracking station (GTS) observations and ISL ranging observations firstly to analyze the impact of the ISL ranging observations on the orbit determination of BDS-3 satellites. Subsequently, considering the data fusion processing, the variance component estimation (VCE) algorithm is applied to the parameter estimation process of the satellite orbit determination. Finally, using the measured data from China’s regional GTS observations and BDS-3 ISL ranging observations, the effects of ISL ranging observations on the orbit determination accuracy of BDS-3 satellites are analyzed. Moreover, the impact of the VCE algorithm on the fusion data processing is evaluated from the aspects of orbit determination accuracy, Ka-band hardware delay parameter stability, and ISL ranging observation residuals. The results show that for China’s regional GTSs, the addition of BDS-3 ISL ranging observations can significantly improve the orbit determination accuracy of BDS-3 satellites. The observed orbit determination accuracy of satellite radial component is improved from 48 cm to 4.1 cm. In addition, when the initial weight ratio between GTS observations and ISL ranging observations is not appropriate, the various indicators which include orbit determination accuracy, ISL hardware delay, and ISL observation residuals were observed to have improved after the adjustment of the VCE algorithm. These results validate the effectiveness of the VCE algorithm for the fusion data processing of the GTS observations and ISL ranging observations.     

基于自适应滤波的编队卫星实时相对定轨

提出基于自适应滤波的编队卫星实时相对定轨算法,利用2005-12-09—10两颗GRACE（Gravity Recovery and Climate Experiment）卫星的GPS（Global Positioning System）实测数据进行实时相对定轨试验计算,采用JPL（Jet Propulsion Laboratory）轨道对试验结果外部检核,结果表明:①自适应滤波相对定轨通过自适应因子,可以较好地平衡编队卫星的观测信息和相对动力学信息,其相对定轨结果精度优于Kalman滤波相对定轨结果;②自适应滤波相对定轨结果随着星间基线缩短而精度提高;③两颗GRACE卫星采用单频伪距和广播星历进行自适应滤波相对定轨,可以得到精度优于6cm的星间基线。     

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.     

Application of BDS-GEO for studying TEC variability in equatorial ionosphere on different time scales

The Earth's ionosphere and especially its equatorial part is a highly dynamical medium. Geostationary satellites are known to be a powerful tool for ionospheric studies. Recent developments in BDS-GEO satellites allow such studies on the new level due to the best noise pattern in TEC estimations, which corresponds to those of GPS/GLONASS systems. Here we used BDS-GEO satellites to demonstrate their capability for studying equatorial ionosphere variability on different time scales. Analyzing data from the equatorial SIN1 IGS station we present seasonal variations in geostationary slant TEC for the periods of high (October 2013 - October 2014) and low (January 2017 - January 2018) solar activity, which show semi-annual periodicity with amplitudes about 10 TECU during solar maximum and about 5 TECU during the solar minimum. The 27-day variations are also prominent in geostationary slant TEC variations, which correlates quite well with the variations in solar extreme UV radiation. We found semi-annual pattern in small scale ionospheric disturbances evaluated based on geostationary ROTI index: maximal values correspond to spring and fall equinoxes and minimum values correspond to summer and winter solstices. The seasonal asymmetry in ROTI values was observed: spring equinox values were almost twice as higher than fall equinox ones. We also present results on the 2017 May 28–29 G3 geomagnetic storm, when ～30 TECU positive anomaly was recorded, minor and final major sudden stratospheric warmings in February and March 2016, with positive daytime TEC anomalies up to 15–20 TECU, as well as the 2017 September 6 X9.3 solar flare with 2 TECU/min TEC rate. Our results show the large potential of geostationary TEC estimations with BDS-GEO signals for continuous monitoring of space weather effects in low-latitude and equatorial ionosphere.     

利用GPS对地球静止轨道卫星定轨的可行性

总结了几种利用 GPS对地球静止轨道卫星定轨的方法 ,并且对仅仅接收 GPS星发射的信号来定轨这种方法进行了计算论证。得出了 GPS星在一个计算周期 (2 4 h)内对于静止卫星的可利用性 ,比较了不同条件下的可利用性。通过对可利用性分析 ,提出了一种利用 GPS对静止卫星定轨的方法     

The NOAA satellites: A largely neglected tool in the land sciences

The NOAA satellite system comprises the polar-orbiting satellites which provide image data twice a day, and the geostationary satellites, which provide image data every 30 minutes. Data is provided in the visible, near infrared, and middle and far thermal infrared at 1 km resolution from the polar-orbiting satellites and in the visible at 1-km resolution and in the far thermal infrared at 8 km resolution from the geostationary satellites. Applications described include monitoring tectonic lineaments in Alaska, monitoring the Greenland Ice Sheet, mapping geomorphology in the Dakotas and monitoring volcano eruptions. Applications of the Heat Capacity Mapping Mission described include discriminating rock types and indications of mineral deposits. Current research into Land Sciences Applications are discussed and recommendations made for further areas of research.     

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.      

Comprehensive outage compensation of real-time orbit and clock corrections with broadcast ephemeris for ambiguity-fixed precise point positioning

The main challenge in real-time precise point positioning (PPP) is that the data outages or large time lags in receiving precise orbit and clock corrections greatly degrade the continuity and real-time performance of PPP positioning. To solve this problem, instead of directly predicting orbit and clock corrections in previous researches, this paper presents an alternative approach of generating combined corrections including orbit error, satellite clock and receiver-related error with broadcast ephemeris. Using ambiguities and satellite fractional-cycle biases (FCBs) of previous epoch and the short-term predicted tropospheric delay through linear extrapolation model (LEM), combined corrections at current epoch are retrieved and weighted with multiple reference stations, and further broadcast to user for continuous enhanced positioning during outages of orbit and clock corrections. To validate the proposed method, two reference station network with different inter-station distance from National Geodetic Survey (NGS) network are used for experiments with six different time lags (i.e., 5 s, 10 s, 15 s, 30 s, 45 s and 60 s), and one set of data collected by unmanned aerial vehicle (UAV) is also used. The performance of LEM is investigated, and the troposphere prediction accuracy of low elevation (e.g., 10–20degrees) satellites has been improved by 44.1% to 79.0%. The average accuracy of combined corrections before and after LEM is used is improved by 12.5% to 77.3%. Without LEM, an accuracy of 2–3 cm can be maintained only in case of small time lags, while the accuracies with LEM are all better than 2 cm in case of different time lags. The performance of simulated kinematic PPP at user end is assessed in terms of positioning accuracy and epoch fix rate. In case of different time lags, after LEM is used, the average accuracy in horizontal direction is better than 3 cm, and the accuracy in up direction is better than 5 cm. At the same time, the epoch fix rate has also increased to varying degrees. The results of the UAV data show that in real kinematic environment, the proposed method can still maintain a positioning accuracy of several centimeters in case of 20 s time lag.     

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.     

Analysis of GNSS clock prediction performance with different interrupt intervals and application to real-time kinematic precise point positioning

Continuous and timely real-time satellite orbit and clock products are mandatory for real-time precise point positioning (RT-PPP). Real-time high-precision satellite orbit and clock products should be predicted within a short time in case of communication delay or connection breakdown in practical applications. For prediction, historical data describing the characteristics of the real-time orbit and clock can be used as the basis for performing the prediction. When historical data are scarce, it is difficult for many existing models to perform precise predictions. In this paper, a linear regression model is used to predict clock products. Seven-day GeoForschungsZentrum (GFZ) final clock products sampled at 30 s are used to analyze the characteristics of GNSS clocks. It is shown that the linear regression model can be used as the prediction model for the satellite clock products. In addition, the accuracy of the clock prediction for different satellites are analyzed using historical data with different periods (such as 2 and 10 epochs). Experimental results show that the accuracy of the clock with the linear regression prediction model using historical data with 10 epochs is 1.0 ns within 900 s. This is higher accuracy than that achieved using historical data of 2 epochs. Finally, the performance analysis for real-time kinematic precise point positioning (PPP) is provided using GFZ final clock prediction results and state space representation (SSR) clock prediction results when communication delay or connection breakdown occur. Experimental results show that the positioning accuracy without prediction is better than that with prediction in general, whether using the final clock product or the SSR clock product. For the final clock product, the positioning accuracy in the north (N), east (E), and up (U) directions is better than 10.0 cm with all visible GNSS satellites with prediction. In comparison, the 3D positioning accuracy of N, E, and U directions with visible GNSS satellites whose prediction accuracy is better than 0.1 ns using historical data of 10 epochs is improved from 15.0 cm to 7.0 cm. For the SSR clock product, the positioning accuracy of N, E, and U directions is better than 12.0 cm with visible GNSS satellites with prediction. In comparison, the 3D positioning accuracy of N, E, and U directions with visible GNSS satellites whose prediction accuracy is better than 0.1 ns using historical data of 10 epochs is improved from 12.0 cm to 9.0 cm.     

基于位置观测的北斗广播星历速度精度分析

利用广播星历计算导航卫星的速度向量是GNSS高精度实时测速的必要条件.本文分析了仅以卫星位置向量为观测量的北斗广播星历的速度计算精度.从广播星历拟合过程出发,推导了北斗18参数模型的速度向量计算公式.基于北斗13颗在轨卫星一年的实际轨道数据,分析了全年广播星历计算卫星速度向量的精度.结果表明,利用18参数模型计算的速度误差最大在10-4m·-1量级;在相同拟合时段条件下,地球静止轨道（GEO）和倾斜地球同步轨道（IGSO）卫星的速度精度相当,高于中圆地球轨道（MEO）卫星.通过对位置残差序列分析,得出位置残差误差较小且变化趋势平稳是广播星历计算速度精度较高的原因.分析和计算结果验证了仅用位置观测量拟合北斗广播星历算法的有效性.      

混合星座导航卫星广播星历相关问题研究

GPS卫星广播星历参数具有参数少、物理意义明确以及精度高等特点,可以考虑将它应用于包含MEO、IGSO和GEO卫星的混合星座卫星导航系统。分析了采用GPs卫星广播星历参数时MEO、IGSO和GEO卫星的广播星历拟合精度,并且比较分析了在一个卫星的轨道周期内,广播星历参数拟合结果的变化规律。仿真结果表明,MEO、IGSO和GEO卫星的广播星历拟合误差最大在分米量级;MEO和IGSO卫星在一个轨道周期内星历参数拟合结果的变化规律相近,但是与GEO卫星的差异较大。     

A review of geostationary satellite alternatives for retrieving data from long duration balloon flights

Low speed data from high altitude scientific balloon flights can be retrieved by geostationary satellites through existing data collection platform systems. Higher speed data of the order of 1 kbit/s create a more difficult problem, particularly if a response is to be made to the balloon payload in near real time. Different geostationary satellite methods to achieve these more demanding requirements are reviewed, and the more interesting cases identified for possible future experiments.     

A new algorithm for optical observations of space debris with the TAROT telescopes

Since 2004, we observe satellites in the geostationary orbit with a network of robotic ground based fully automated telescopes called TAROT. One of them is located in France and the second at ESO, La Silla, Chile. The system processes the data in real time. Its wide field of view is useful for the discovery, the systematic survey and for the tracking of both catalogued and un-catalogued objects. We present a new source extraction algorithm based on morphological mathematic, which has been tested and is currently under implementation in the standard pipeline. Using this method, the observation strategy will correlate the measurements of the same object on successive images and give better detection rate and false alarm rate than the previous one. The overall efficiency and quality of the survey of the geostationary orbit has drastically improved and we can now detect satellites and debris in different orbits like Geostationary Transfer Orbit (GTO). Results obtained in real conditions with TAROT are presented.