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Muriel Bergé-Nguyen Jean-François Cretaux Stéphane Calmant Sarah Fleury Rysbek Satylkanov D. Chontoev Pascal Bonnefond 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(3):985-1001
Lake water height is a key variable in water cycle and climate change studies, which is achievable using satellite altimetry constellation. A method based on data processing of altimetry from several satellites has been developed to interpolate mean lake surface (MLS) over a set of 22 big lakes distributed on the Earth. It has been applied on nadir radar altimeters in Low Resolution Mode (LRM: Jason-3, Saral/AltiKa, CryoSat-2) in Synthetic Aperture Radar (SAR) mode (Sentinel-3A), and in SAR interferometric (SARin) mode (CryoSat-2), and on laser altimetry (ICESat). Validation of the method has been performed using a set of kinematic GPS height profiles from 18 field campaigns over the lake Issykkul, by comparison of altimetry’s height at crossover points for the other lakes and using the laser altimetry on ICESat-2 mission. The precision reached ranges from 3 to 7 cm RMS (Root Mean Square) depending on the lakes. Currently, lake water level inferred from satellite altimetry is provided with respect to an ellipsoid. Ellipsoidal heights are converted into orthométric heights using geoid models interpolated along the satellite tracks. These global geoid models were inferred from geodetic satellite missions coupled with absolute and regional anomaly gravity data sets spread over the Earth. However, the spatial resolution of the current geoid models does not allow capturing short wavelength undulations that may reach decimeters in mountaineering regions or for rift lakes (Baikal, Issykkul, Malawi, Tanganika). We interpolate in this work the geoid height anomalies with three recent geoid models, the EGM2008, XGM2016 and EIGEN-6C4d, and compare them with the Mean Surface of 22 lakes calculated using satellite altimetry. Assuming that MLS mimics the local undulations of the geoid, our study shows that over a large set of lakes (in East Africa, Andean mountain and Central Asia), short wavelength undulations of the geoid in poorly sampled areas can be derived using satellite altimetry. The models used in this study present very similar geographical patterns when compared to MLS. The precision of the models largely depends on the location of the lakes and is about 18 cm, in average over the Earth. MLS can serve as a validation dataset for any future geoid model. It will also be useful for validation of the future mission SWOT (Surface Water and Ocean Topography) which will measure and map water heights over the lakes with a high horizontal resolution of 250 by 250 m. 相似文献
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Wenwu Ding Bingfeng Tan Yongchang Chen Felix Norman Teferle Yunbin Yuan 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(3):951-961
The performance of real-time (RT) precise positioning can be improved by utilizing observations from multiple Global Navigation Satellite Systems (GNSS) instead of one particular system. Since the end of 2012, BeiDou, independently established by China, began to provide operational services for users in the Asia-Pacific regions. In this study, a regional RT precise positioning system is developed to evaluate the performance of GPS/BeiDou observations in Australia in providing high precision positioning services for users. Fixing three hourly updated satellite orbits, RT correction messages are generated and broadcasted by processing RT observation/navigation data streams from the national network of GNSS Continuously Operating Reference Stations in Australia (AUSCORS) at the server side. At the user side, RT PPP is realized by processing RT data streams and the RT correction messages received. RT clock offsets, for which the accuracy reached 0.07 and 0.28?ns for GPS and BeiDou, respectively, can be determined. Based on these corrections, an accuracy of 12.2, 30.0 and 45.6?cm in the North, East and Up directions was achieved for the BeiDou-only solution after 30 min while the GPS-only solution reached 5.1, 15.3 and 15.5?cm for the same components at the same time. A further improvement of 43.7, 36.9 and 45.0 percent in the three directions, respectively, was achieved for the combined GPS/BeiDou solution. After the initialization process, the North, East and Up positioning accuracies were 5.2, 8.1 and 17.8?cm, respectively, for the BeiDou-only solution, while 1.5, 3.0, and 4.7?cm for the GPS-only solution. However, we only noticed a 20.9% improvement in the East direction was obtained for the GPS/BeiDou solution, while no improvements in the other directions were detected. It is expected that such improvements may become bigger with the increasing accuracy of the BeiDou-only solution. 相似文献
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主要介绍了刹车装置性能试验台的实现机理、采用的方案,有助于增进对液压试验台设计和可编程控制器PLC应用方面的了解。 相似文献
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介绍某些战术导弹折叠翼快速展开特性测试技术。详细地介绍了测量方法、项目、数据处理和主要结果。试验是在北京空气动力研究所一座低速风洞中进行的。试验结果表明,获得的数据具有很高精度和可靠性,重复性也是令人满意的。 相似文献
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任意波发生器静态特性的评价 总被引:3,自引:1,他引:2
介绍了任意波发生器的主要静态特性指标、校准方法及实现过程。通过一组实验.获得了实际校准结果,并对校准中需要注意的问题进行了讨论。所述方法涉及的静态特性内容比较全面。具有足够的测量准确度、分辨力和稳定性。可用于任意波发生器的静态指标评价和计量。 相似文献
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进行自由空间的光通信或空间对抗,需要在卫星间实现精确的跟踪与瞄准。因为地面测控站的设置非常有限,指令与数据注入的范围受到很多限制,所以要求这种跟瞄在很多时候是无主控制状态下完成的。提出了一种利用在地面测控站的范围内向星上数管中心注入目标卫星、本体卫星的轨道参数,其它时间依靠自主导航飞行和GPS修正的方法,结合本体星的姿态测量、振动测量实现卫星瞄准指向的方位角与俯仰角的精确控制的方法,提高了在地面站无法注入指令与数据时卫星的捕获概率。通过仿真,将计算结果与卫星仿真工具软件STK的数据进行比较,结果一致。最后在嵌入式DSP平台上实现了这一策略。 相似文献
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针对机载设备二类检测设备将故障隔离到SRU的要求,对LRU的内部结构进行了分析,提出了点、底项、组底项的概念,用关联值表示点与点之间、点与SRU之间及组底项之间的关联关系;针对多SRU结构UUT,提出逐级排除法故障诊断方法. 相似文献