共查询到20条相似文献，搜索用时 31 毫秒
1.
J. Klokoník J. Kostelecký C.A. Wagner P. Schwintzer Ch. Förste R. Scharroo 《Journal of Geodesy》2005,78(7-8):405-417
Since the advent of CHAMP, the first in a series of low-altitude satellites being almost continuously and precisely tracked by GPS, a new generation of long-wavelength gravitational geopotential models can be derived. The accuracy evaluation of these models depends to a large extent on the comparison with external data of comparable quality. Here, two CHAMP-derived models, EIGEN-1S and EIGEN-2, are tested with independent long-term-averaged single satellite crossover (SSC) sea heights from three altimetric satellites (ERS-1, ERS-2 and Geosat). The analyses show that long-term averages of crossover residuals still are powerful data to test CHAMP gravity field models. The new models are tested in the spatial domain with the aid of ERS-1/-2 and Geosat SSCs, and in the spectral domain with latitude-lumped coefficient (LLC) corrections derived from the SSCs. The LLC corrections allow a representation of the satellite-orbit-specific error spectra per order of the models spherical harmonic coefficients. These observed LLC corrections are compared to the LLC projections from the models variance–covariance matrix. The excessively large LLC errors at order 2 found in the case of EIGEN-2 with the ERS data are discussed. The degree-dependent scaling factors for the variance-covariance matrices of EIGEN-1S and –2, applied to obtain more realistic error estimates of the solved-for coefficients, are compatible with the results found here. 相似文献
2.
Zhigui Kang Byron Tapley Jianli Chen John Ries Srinivas Bettadpur 《Journal of Geodesy》2009,83(10):895-901
Two 4.5-year sets of daily geocenter variations have been derived from GPS-LEO (Low-Earth Orbiter) tracking of the GRACE (Gravity
Recovery And Climate Experiment) satellites. The twin GRACE satellites, launched in March 2002, are each equipped with a BlackJack
global positioning system (GPS) receiver for precise orbit determination and gravity recovery. Since launch, there have been
significant improvements in the background force models used for satellite orbit determination, most notably the model for
the geopotential, which has resulted in significant improvements to the orbit determination accuracy. The purpose of this
paper is to investigate the potential for determining seasonal (annual and semiannual) geocenter variations using GPS-LEO
tracking data from the GRACE twin satellites. Internal comparison between the GRACE-A and GRACE-B derived geocenter variations
shows good agreement. In addition, the annual and semiannual variations of geocenter motions determined from this study have
been compared with other space geodetic solutions and predictions from geophysical models. The comparisons show good agreement
except for the phase of the z-translation component. 相似文献
3.
Satellite gravity missions, such as CHAMP, GRACE and GOCE, and airborne gravity campaigns in areas without ground gravity will enhance the present knowledge of the Earths gravity field. Combining the new gravity information with the existing marine and ground gravity anomalies is a major task for which the mathematical tools have to be developed. In one way or another they will be based on the spectral information available for gravity data and noise. The integration of the additional gravity information from satellite and airborne campaigns with existing data has not been studied in sufficient detail and a number of open questions remain. A strategy for the combination of satellite, airborne and ground measurements is presented. It is based on ideas independently introduced by Sjöberg and Wenzel in the early 1980s and has been modified by using a quasi-deterministic approach for the determination of the weighting functions. In addition, the original approach of Sjöberg and Wenzel is extended to more than two measurement types, combining the Meissl scheme with the least-squares spectral combination. Satellite (or geopotential) harmonics, ground gravity anomalies and airborne gravity disturbances are used as measurement types, but other combinations are possible. Different error characteristics and measurement-type combinations and their impact on the final solution are studied. Using simulated data, the results show a geoid accuracy in the centimeter range for a local test area. 相似文献
4.
Energy integral method for gravity field determination from satellite orbit coordinates 总被引：22，自引：1，他引：21
A fast iterative method for gravity field determination from low Earth satellite orbit coordinates has been developed and implemented successfully. The method is based on energy conservation and avoids problems related to orbit dynamics and initial state. In addition, the particular geometry of a repeat orbit is exploited by using a very efficient iterative estimation scheme, in which a set of normal equations is approximated by a sparse block-diagonal equivalent. Recovery experiments for spherical harmonic gravity field models up to degree and order 80 and 120 were conducted based on a 29-day simulated data set of orbit coordinates. The method was found to be very flexible and could be easily adapted to include observations of non-conservative accelerations, such as (to be) provided by satellites like CHAMP, GRACE, and GOCE. A serious drawback of the method is its large sensitivity to satellite velocity errors. Existing orbit determination strategies need to be altered or augmented to include algorithms that focus on optimizing the accuracy of estimated velocities. 相似文献
5.
现代低轨卫星对地球重力场探测的实践和进展 总被引：4，自引：4，他引：4
综述了现代低轨卫星对地球重力场测量的特点和近况，介绍了已经和即将发射的重力卫星CHAMP、GRACE、GOCE和新型测高卫星，讨论了作为现代重力卫星首次实践－－CHAMP卫星的进展和目前尚待解决的问题。 相似文献
6.
A preliminary commission error analysis whereby orbit perturbation theory and other techniques are used to assess and predict the recovery of the Earths gravity field from the challenging microsatellite payload (CHAMP) mission is developed and implemented. With CHAMP launched in July 2000, accumulated evidence is now available to quantify the errors in the recovery procedure including the orbital precision from GPS, attitude errors, accelerometer noise and thruster mismatch/misalignment. For the latter, numerical integrations using a variable length single-step Runge–Kutta integrator and a fixed length multi-step method are compared to assess the error associated with assuming that the thruster misalignment can be spread uniformly across a step interval. Error degree variances from simulated studies are compared to results from a recently released CHAMP-based gravity field, EIGEN-1S. It is seen that the orbital positioning, as derived from the onboard GPS receiver, is critical, with accelerometer noise contributing at a lower level. Attitude error, at currently quoted accuracy, is not significant as an error source.
AcknowledgementsThe authors would like to thank the UK Natural Environment Research Council (Grant No. NER/A/0000/00612) for financing this study and GFZ for supplying the data and technical support. 相似文献
7.
Is the long-term variation of the estimated GPS differential code biases associated with ionospheric variability? 总被引：1，自引：0，他引：1
The global positioning system (GPS) differential code biases (DCB) provided by the International GNSS Service (IGS) show solar-cycle-like variation during 2002–2013. This study is to examine whether this variation of the GPS DCBs is associated with ionospheric variability. The GPS observations from low earth orbit (LEO) satellites including CHAMP, GRACE and Jason-1 are used to address this issue. The GPS DCBs estimated from the LEO-based observations at different orbit altitudes show a similar tendency as the IGS DCBs. However, this solar-cycle-like dependency is eliminated when the DCBs of 13 continuously operating GPS satellites are constrained to zero-mean. Our results thus revealed that ionospheric variation is not responsible for the long-term variation of the GPS DCBs. Instead, it is attributed to the GPS satellite replacement with different satellite types and the zero-mean condition imposed on all satellite DCBs. 相似文献
8.
Cheinway Hwang Tzu-Pang Tseng Ting-Jung Lin Dražen Švehla Urs Hugentobler Benjamin Fong Chao 《GPS Solutions》2010,14(1):121-131
The precise orbit determination antennas of F3/C and GRACE-A satellites are from the same manufacturer, but are installed
in different configurations. The current orbit accuracy of F3/C is 3 cm at arcs with good GPS data, compared to 1 cm of GRACE,
which has a larger ratio of usable GPS data. This paper compares the qualities of GPS observables from F3/C and GRACE. Using
selected satellites and time spans, the following average values for the satellite F3/C and satellite A of GRACE are obtained:
multipath effect on the pseudorange P1, 0.78 and 0.38 m; multipath effect on the pseudorange P2, 1.03 and 0.69 m; occurrence
frequency of cycle slip, 1/29 and 1/84; standard error of unit weight, 4 and 1 cm; dynamic–kinematic orbit difference, 10
and 2 cm. For gravity determination using F3/C GPS data, a careful selection of GPS data is critical. With six satellites
in orbit, F3/C’s large amount of GPS data will make up the deficiency in data quality. 相似文献
9.
The Center for Orbit Determination in Europe (CODE) has been involved in the processing of combined GPS/GLONASS data during the International GLONASS Experiment (IGEX). The resulting precise orbits were analyzed using the program SORBDT. Introducing one satellites positions as pseudo-observations, the program is capable of fitting orbital arcs through these positions using an orbit improvement procedure based on the numerical integration of the satellites orbit and its partial derivative with respect to the orbit parameters. For this study, the program was enhanced to estimate selected parameters of the Earths gravity field. The orbital periods of the GPS satellites are —in contrast to those of the GLONASS satellites – 2:1 commensurable (P
Sid:P
GPS) with the rotation period of the Earth. Therefore, resonance effects of the satellite motion with terms of the geopotential occur and they influence the estimation of these parameters. A sensitivity study of the GPS and GLONASS orbits with respect to the geopotential coefficients reveals that the correlations between different geopotential coefficients and the correlations of geopotential coefficients with other orbit parameters, in particular with solar radiation pressure parameters, are the crucial issues in this context. The estimation of the resonant geopotential terms is, in the case of GPS, hindered by correlations with the simultaneously estimated radiation pressure parameters. In the GLONASS case, arc lengths of several days allow the decorrelation of the two parameter types. The formal errors of the estimates based on the GLONASS orbits are a factor of 5 to 10 smaller for all resonant terms.
AcknowledgmentsThe authors would like to thank all the organizations involved in the IGS and the IGEX campaign, in particular those operating an IGS or IGEX observation site and providing the indispensable data for precise orbit determination. 相似文献
10.
GNSS observations provided by the global tracking network of the International GNSS Service (IGS, Dow et al. in J Geod 83(3):191–198, 2009) play an important role in the realization of a unique terrestrial reference frame that is accurate enough to allow a detailed monitoring of the Earth’s system. Combining these ground-based data with GPS observations tracked by high-quality dual-frequency receivers on-board low earth orbiters (LEOs) is a promising way to further improve the realization of the terrestrial reference frame and the estimation of geocenter coordinates, GPS satellite orbits and Earth rotation parameters. To assess the scope of the improvement on the geocenter coordinates, we processed a network of 53 globally distributed and stable IGS stations together with four LEOs (GRACE-A, GRACE-B, OSTM/Jason-2 and GOCE) over a time interval of 3 years (2010–2012). To ensure fully consistent solutions, the zero-difference phase observations of the ground stations and LEOs were processed in a common least-squares adjustment, estimating all the relevant parameters such as GPS and LEO orbits, station coordinates, Earth rotation parameters and geocenter motion. We present the significant impact of the individual LEO and a combination of all four LEOs on the geocenter coordinates. The formal errors are reduced by around 20% due to the inclusion of one LEO into the ground-only solution, while in a solution with four LEOs LEO-specific characteristics are significantly reduced. We compare the derived geocenter coordinates w.r.t. LAGEOS results and external solutions based on GPS and SLR data. We found good agreement in the amplitudes of all components; however, the phases in x- and z-direction do not agree well. 相似文献
11.
Zhigui Kang Byron Tapley Srinivas Bettadpur John Ries Peter Nagel Rick Pastor 《Journal of Geodesy》2006,80(6):322-331
The GRACE (gravity recovery and climate experiment) satellites, launched in March 2002, are each equipped with a BlackJack GPS onboard receiver for precise orbit determination and gravity field recovery. Since launch, there have been significant improvements in the background force models used for satellite orbit determination, most notably the model for the geopotential. This has resulted in significant improvements to orbit accuracy for very low altitude satellites. The purpose of this paper is to investigate how well the orbits of the GRACE satellites (about 470 km in altitude) can currently be determined using only GPS data and based on the current models and methods. The orbit accuracy is assessed using a number of tests, which include analysis of orbit fits, orbit overlaps, orbit connecting points, satellite Laser ranging residuals and K-band ranging (KBR) residuals. We show that 1-cm radial orbit accuracy for the GRACE satellites has probably been achieved. These precise GRACE orbits can be used for such purposes as improving gravity recovery from the GRACE KBR data and for atmospheric profiling, and they demonstrate the quality of the background force models being used. 相似文献
12.
Marine gravity surveying line system adjustment 总被引：6，自引：0，他引：6
Huang Motao 《Journal of Geodesy》1995,70(3):158-165
The general theories and methods of marine surveying line system adjustment were introduced in (1979) and Tang (1991) . According to the characteristics of marine gravity measurement, this paper presents a new method of combined adjustment which takes into account both direct and indirect influence of position errors. The method is particularly suitable to be used in the post- processing of marine gravity observation data. With some practical applications, it is proved to be effective in improving the quality of marine gravity data. 相似文献
13.
应用GRACE卫星数据反演高精度静态地球重力场是大地测量学界的热点之一。考虑到经典动力学法线性化误差随弧长拉长而迅速增长,本文以GRACE卫星轨道观测值为初值的线性化方法,建立了应用GRACE卫星轨道和星间距离变率反演地球重力场的改进动力学法理论模型。利用2003年1月至2010年12月的GRACE卫星姿态、轨道、星间距离变率和非保守力加速度等观测数据,解算了一个180阶次的无约束全球静态重力场模型Tongji-Dyn01s和一个采用Kaula规则约束的全球重力场模型Tongji-Dyn01k。与国际不同机构最新发布的纯GRACE数据解算的重力场模型(包括AIUB-GRACE03S、GGM05S、ITSG-Grace2014k和Tongji-GRACE01)进行比较,并利用DTU13海洋重力异常和GPS/水准高程异常进行外部检核,结果表明,Tongji-Dyn01s与国际最新模型精度处于同一水平,然而Tongji-Dyn01k模型总体上更加靠近EIGEN6C2重力场模型。 相似文献
14.
The value of ocean reflections of GPS signals to enhance satellite altimetry: data distribution and error analysis 总被引：4，自引：0，他引：4
The time and space distribution of general reflection altimetry from two satellites (senders and receivers) via the the oceans surface is examined with specific reference to GPS senders and two current receiving satellites. While a considerable enhancement of conventional altimeter coverage is possible in all configurations if the reflection signals can be used, repeating passes of these (with GPS senders) having reasonably small cycle times (days to tens of days) occur only if the receiving orbit is nearly polar. Results of an analysis of the fundamental geometry show that over a large range of reflection angles the error of recovered sea heights depends almost entirely on the errors in the delay signal and the radial error of the receiving satellite (using current estimates of GPS orbit accuracies). The most critical element is the precision of the delay measurement. Both it and the accuracy of the receiving orbit should be below the decimeter level for the technique to achieve its full potential. 相似文献
15.
国际重力卫星研究进展和我国将来卫星重力测量计划 总被引：12，自引：3，他引：9
本文首先分别介绍了国际已经成功发射的专用地球重力测量卫星CHAMP、GRACE以及即将发射的GOCE、GRACE Follow-On和专用月球重力探测卫星GRAIL的研制机构、轨道参数、关键载荷、跟踪模式、测量原理、科学目标和技术特征;其次,阐述了当前相关学科对地球重力场测量精度的需求;最后,建议我国在将来实施的卫星重力测量计划中首选卫星跟踪卫星高低\低低模式,尽快开展轨道参数优化选取的定量系统研究论证和重力卫星系统的误差分析,依据匹配精度指标先期开展重力卫星各关键载荷的研制以及尽早启动卫星重力测量系统的虚拟仿真研究。 相似文献
16.
Daniel Koenig 《Journal of Geodesy》2018,92(11):1299-1312
Applying a one-step integrated process, i.e. by simultaneously processing all data and determining all satellite orbits involved, a Terrestrial Reference Frame (TRF) consisting of a geometric as well as a dynamic part has been determined at the observation level using the EPOS-OC software of Deutsches GeoForschungsZentrum. The satellite systems involved comprise the Global Positioning System (GPS) as well as the twin GRACE spacecrafts. Applying a novel approach, the inherent datum defect has been overcome empirically. In order not to rely on theoretical assumptions this is done by carrying out the TRF estimation based on simulated observations and using the associated satellite orbits as background truth. The datum defect is identified here as the total of all three translations as well as the rotation about the z-axis of the ground station network leading to a rank-deficient estimation problem. To rectify this singularity, datum constraints comprising no-net translation (NNT) conditions in x, y, and z as well as a no-net rotation (NNR) condition about the z-axis are imposed. Thus minimally constrained, the TRF solution covers a time span of roughly a year with daily resolution. For the geometric part the focus is put on Helmert transformations between the a priori and the estimated sets of ground station positions, and the dynamic part is represented by gravity field coefficients of degree one and two. The results of a reference solution reveal the TRF parameters to be estimated reliably with high precision. Moreover, carrying out a comparable two-step approach using the same data and models leads to parameters and observational residuals of worse quality. A validation w.r.t. external sources shows the dynamic origin to coincide at a level of 5 mm or better in x and y, and mostly better than 15 mm in z. Comparing the derived GPS orbits to IGS final orbits as well as analysing the SLR residuals for the GRACE satellites reveals an orbit quality on the few cm level. Additional TRF test solutions demonstrate that K-Band Range-Rate observations between both GRACE spacecrafts are crucial for accurately estimating the dynamic frame’s orientation, and reveal the importance of the NNT- and NNR-conditions imposed for estimating the components of the dynamic geocenter. 相似文献
17.
Different types of GPS clock and orbit data provided by the International GPS Service (IGS) have been used to assess the accuracy
of rapid orbit determination for satellites in low Earth orbit (LEO) using spaceborne GPS measurements. To avoid the need
for reference measurements from ground-based reference receivers, the analysis is based on an undifferenced processing of
GPS code and carrier-phase measurements. Special attention is therefore given to the quality of GPS clock data that directly
affects the resulting orbit determination accuracy. Interpolation of clock data from the available 15 min grid points is identified
as a limiting factor in the use of IGS ultra-rapid ephemerides. Despite this restriction, a 10-cm orbit determination accuracy
can be obtained with these products data as demonstrated for the GRACE-B spacecraft during selected data arcs between 2002
and 2004. This performance may be compared with a 5-cm orbit determination accuracy achievable with IGS rapid and final products
using 5 min clock samples. For improved accuracy, high-rate (30 s) clock solutions are recommended that are presently only
available from individual IGS centers. Likewise, a reduced latency and more frequent updates of IGS ultra-rapid ephemerides
are desirable to meet the requirements of upcoming satellite missions for near real-time and precise orbit determination. 相似文献
18.
Estimation of elevation-dependent satellite antenna phase center variations of GPS satellites 总被引：16，自引：7，他引：9
A method for the estimation of the phase center variations of GPS satellite antennas using global GPS data is presented. First estimations have shown an encouraging repeatability from day to day and between satellites of the same block. Thus, two different satellite antenna patterns for Block II/IIA and for Block IIR with a range of about 4 cm and an accuracy of less than 1 mm could be found. The present approach allows the creation of a consistent set of receiver and satellite antenna patterns and phase center offsets. Thereby, it is possible to switch from relative to absolute phase center variations without a scale problem in global networks. This changeover has an influence on troposphere parameters, reduces systematic effects due to uncorrect antenna modeling and should diminish the elevation dependence of GPS results.
AcknowledgmentsThe authors thank Prof. G. Seeber (University of Hannover) and Dr. G. Wübbena (Geo++ GmbH) and their groups for their kindness in making available the absolute field calibration results derived from robot measurements. 相似文献
19.
重力卫星主要有效载荷指标分析与确定 总被引：5，自引：1，他引：5
在介绍重力卫星发展计划的基础上 ,研究讨论了重力卫星上的主要有效载荷。从重力测量的基本原理出发 ,推导了卫星轨道高度、有效荷载的精度需求、所能恢复的重力场最大空间分辨率和相应重力场参数精度之间粗略的函数关系。最后利用推导的公式计算了CHAMP、GRACE、GOCE卫星上几种主要测量有效载荷的指标 ,并将推得的指标与CHAMP、GRACE、GOCE卫星设计的指标进行了比较 ,得出了两种指标在量级上一致的结论。 相似文献
20.
This study makes an initial comparison of three GPS-like constellations. Starting with a simplified constellation of 25 GPS satellites as a reference, GPS(25), we determine what kinematic positioning improvements would result from a constellation comprising a Hi component of 16 GPS satellites (at roughly 16.8 earth radii) coupled with a Lo component of 49 GPS satellites (at roughly 2.1 earth radii). We also include a GPS constellation of 49 GPS satellites, GPS(49), which comprises orbits like the GPS(25) constellation. The GPS(49) and the Hi(16)/Lo(49) constellations have semi-major axes selected so that they have exactly the same average number of satellites above 7.5 degrees elevation (averaged over 24 hours). What motivated this study was a need to measure the benefits, to precision differential kinematic positioning methods (i.e., RTK), which result from the higher Doppler shifts (hence speedier integrated Doppler) generated by the Lo component. Quicker initial convergence was anticipated, of course. 相似文献