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211.
高精度卫星轨道是提高卫星应用水平的基础,卫星精密定轨方法主要基于卫星轨道动力学理论.通过跟踪卫星轨迹的测轨技术,将几何和动力学信息进行融合。地震电磁卫星拟采用星载GPS和综合轨道求解方法进行精密定轨.并辅之以人卫激光测距,其定轨的精度可达厘米级。 相似文献
212.
In calculating the orbit of a minor planet with a least-squares algorithm, current practice is to assume that all observations of a given era have the same uncertainty, and that the errors in these observations are uncorrelated. These assumptions are unrealistic; and they lead to sub-optimal orbits.Our objective is to develop and validate an observational error model that provides realistic estimates of the uncertainties and correlations in asteroid observations. When used to populate the covariance matrix of the least-squares algorithm, the resulting orbits are shown to more accurately and precisely represent asteroid trajectories. 相似文献
213.
S. Marchi M. Massironi G. Cremonese E. Martellato L. Giacomini L. Prockter 《Planetary and Space Science》2011,59(15):1968-1980
In this paper we present a crater age determination of several terrains associated with the Raditladi and Rachmaninoff basins. These basins were discovered during the first and third MESSENGER flybys of Mercury, respectively. One of the most interesting features of both basins is their relatively fresh appearance. The young age of both basins is confirmed by our analysis on the basis of age determination via crater chronology. The derived Rachmaninoff and Raditladi basin model ages are about 3.6 Ga and 1.1 Ga, respectively. Moreover, we also constrain the age of the smooth plains within the basins' floors. This analysis shows that Mercury had volcanic activity until recent time, possibly to about 1 Ga or less. We find that some of the crater size-frequency distributions investigated suggest the presence of a layered target. Therefore, within this work we address the importance of considering terrain parameters, as geo-mechanical properties and layering, into the process of age determination. We also comment on the likelihood of the availability of impactors able to form basins with the sizes of Rachmaninoff and Raditladi in relatively recent times. 相似文献
214.
With the implementation of the Jason-1 satellite altimeter mission, the goal of reaching the 1-cm level in orbit accuracy was set. To support the Precision Orbit Determination (POD) requirements, the Jason-1 spacecraft carries receivers for DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) and GPS (Global Positioning System), as well as a retroreflector for SLR (Satellite Laser Ranging). The overall orbit accuracy for Jason will depend on the quality and the relative weighting of the available tracking data. In this study, the relative importance of the SLR, DORIS, and GPS tracking data is assessed along with the most effective parameterization for accounting for the unmodeled accelerations through the application of empirical accelerations. The optimal relative weighting for each type of tracking data was examined. It is demonstrated that GPS tracking alone is capable of supporting a radial orbit accuracy for Jason-1 at the 1-cm level, and that including SLR tracking provides additional benefits. It is also shown that the GRACE (Gravity Recovery and Climate Experiment) gravity model GGM01S provides a significant improvement in the orbit accuracy and reduction in the level of geographically correlated orbit errors. 相似文献
215.
BRUCE HAINES YOAZ BAR-SEVER WILLY BERTIGER SHAILEN DESAI PASCAL WILLIS 《Marine Geodesy》2013,36(1-2):299-318
The U.S./French Jason-1 satellite is carrying a state-of-the-art GPS receiver to support precise orbit determination (POD) requirements. The performance of the Jason-1 “BlackJack” GPS receiver was strongly reflected in early POD results from the mission, enabling radial accuracies of 1–2 cm soon after the satellite's 2001 launch. We have made further advances in the GPS-based POD for Jason-1, most notably in describing the phase center variations of the on-board GPS antenna. We have also adopted new geopotential models from the Gravity Recovery and Climate Experiment (GRACE). The new strategies have enabled us to better exploit the unique contributions of the BlackJack GPS tracking data in the POD process. Results of both internal and external (e.g., laser ranging) comparisons indicate that orbit accuracies of 1 cm (radial RMS) are being achieved for Jason-1 using GPS data alone. 相似文献
216.
深度基准传递方法的比较与验潮站网基准的综合确定 总被引:1,自引:0,他引:1
分析了深度基准确定的不同方法及由此产生的理论最低潮面含义不一致性。重点比较研究了在长期站基准值的控制下,传递确定短期和临时验潮站深度基准的多种技术方法。以某水深测量工程实例对测区验潮站网深度基准值的统一、协调确定进行了示范论证。得出的基本结论是:在当今深度基准基础框架不完备的现实条件下,水深测量工程区域的深度基准应由所布设的短期和临时验潮站与测区及附近长期验潮站组网确定。确定方法应尽量利用实际观测信息,依据潮差比或略最低潮面比等不同方法传递,并依据规定的限差指标检核。示范实例的计算表明,由不同基准站、不同方法传递确定同一短期验潮站深度基准值的差异可控制在10cm以内。 相似文献
217.
218.
???DNSC08-GRA????е????????????????????????????????Stokes??????????????????????????????????????????????Stokes????????-??????????????????3.4 cm???????????????????????????????GPS/????????м??????????????????????1.17 m???????????????С?7 cm?? 相似文献
219.
????JPL DE?????????洢??????????????????????????????????DE??????????????????????????20???DE406?????????????369 kb????????1/6????GPS??????????ü???DE????????????????????飬?????????60?????????????????????3 m???ü??????????????????????????????????????????????С?????????洢??????????????????????Ч??? 相似文献
220.
《水文科学杂志》2012,57(1):87-101
ABSTRACTThe coefficient of determination R2 and Pearson correlation coefficient ρ = R are standard metrics in hydrology for the evaluation of the goodness of fit between model simulations and observations, and as measures of the degree of dependence of one variable upon another. We show that the standard product moment estimator of ρ, termed r, while well-behaved for bivariate normal data, is upward biased and highly variable for bivariate non-normal data. We introduce three alternative estimators of ρ which are nearly unbiased and exhibit much less variability than r for non-normal data. We also document remarkable upward bias and tremendous increases in variability associated with r using both synthetic data and daily streamflow simulations from 905 calibrated rainfall–runoff models. We show that estimators of ρ = R accounting for skewness are needed for daily streamflow series because they exhibit high variability and skewness compared to, for example, monthly/annual series, where r should perform well. 相似文献