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1.
Summary New Latitude Lumped Coefficients (LLC) of a geopotential model are defined as representing the principal differences of the radial distance to a satellite due to the model at single-orbit crossovers in an Exact Repeat Mission. In contrast with previously defined orbital lumped coefficients, the LLC here are dependent only on the geopotential order (without degree distinction) and the latitude. We examine discrepancies in altimetrically determined sea surface heights at over 30000 crossover positions of GEOSAT during its ERM, 1986–1989, after removal of many variable media and surface effects (Cheney et al., 1991) as well as initial condition orbit error. The mean of these discrepancies along well represented latitude bands in the southern hemisphere are used to determine the LLC errors for Goddard Earth Model T2, which was the reference for the GEOSAT sea surface heights. GEM T2 was derived from satelliteonly tracking data with good representation of the GEOSAT orbit. Relating the measured LLC discrepancies to projections of commission error from the GEM T2 variance-covariance matrix, we find that — except for order 3 — GEM T2's performance is as expected. This test represents the first spectral calibration of a gravity model with independent, purely radial orbit data. 相似文献
2.
Aliasing of the diurnal and semi-diurnal tides is a major problem when estimating the ocean tides from satellite altimetry.
As a result of aliasing, the tides become correlated and many years of altimeter observations may be needed to seperate them.
For the three major satellite altimetry missions to date i.e., GEOSAT, ERS-1, and TOPEX/POSEIDON (T/P), the alias periods
as well as the Rayleigh periods over which the tides decorrelate can be identified. Especially in case of GEOSAT and ERS-1,
severe correlation problems arise. However, it is shown by means of covariance analyses that the tidal phase advance differences
on crossing satellite groundtracks can significantly reduce the correlations among the diurnal and semi-diurnal tides and
among these tides and the seasonal cycles of ocean variability. Therefore, it has been attempted to solve a multi-satellite
response tidal solution for the diurnal and semi-diurnal bands from a total of 7 years of altimetry. Unfortunately, it could
be shown that the GEOSAT and ERS-1 orbit errors are too large to improve a 3-year T/P tidal solution with about 2 years of
GEOSAT and 2 years of ERS-1 altimeter observations. However, these results are preliminary and it is expected that more accurate
orbits, which have become available recently for ERS-1, and additional altimeter data from ERS-2 and the GEOSAT Follow-On
(GFO) should lead to an improved T/P tidal model.
Received: 4 May 1999 / Accepted: 24 January 2000 相似文献
3.
The second European Remote Sensing satellite ERS-2, launched in 1995, is supported by satellite laser ranging (SLR), the
German precise range and range-rate equipment (PRARE) microwave tracking system, and radar altimetry (RA). SLR, PRARE and
crossover RA observations (XO/RA) from May, June, and July 1996 have been analyzed using the GEOSAT software developed at
Forsvarets forskningsinstitutt (FFI, The Norwegian defence research establishment). Orbits computed with the JGM3 gravity
model and the more recent EGM96 gravity model have been compared with orbits from other analysis centers. Based on these comparisons
in addition to the post-fit observation residuals, and results from internal orbital overlaps, we conclude that the radial
component of the ERS-2 orbit can be determined with a precision of 6 cm.
Received: 30 June 1997 / Accepted: 4 February 1998 相似文献
4.
M. C. Kim 《Journal of Geodesy》1997,71(12):749-767
The fundamental geometry of satellite ground tracks and their crossover problem are investigated. For idealized nominal ground
tracks, the geometry is governed by a few constant parameters whose variations lead to qualitative changes in the crossover
solutions. On the basis that the theory to locate crossovers has not been studied in sufficient detail, such changes are described
in regard to the number of crossover solutions in conjunction with their bifurcations. Employing the spinor algebra as a tool
for establishing the ground-track crossing condition, numerical methodologies to locate crossovers appearing in general dual-satellite
ground-track configurations are also presented. The methodologies are applied to precisely determined orbital ephemerides
of the GEOSAT, ERS-1, and TOPEX/POSEIDON altimeter satellites.
Received: 19 November 1996 / Accepted: 12 May 1997 相似文献
5.
Latitude-lumped coefficients (LLC) are defined, representing geopotential-orbit variations for dual-satellite crossovers (DSC). Formulae are derived for their standard errors from the covariances of geopotential field models. Numerical examples are
presented for pairs of the altimeter-bearing satellites TOPEX/Poseidon, ERS 1, and Geosat, using the error matrices of recent
gravity models. The DSC, connecting separate missions, will play an increasingly important role in oceanography spanning decades
only when its nonoceanographic signals are thoroughly understood. In general, the content of even the long-term averaged DSC
is more complex then their single satellite crossover (SSC) counterpart. The LLC, as the spatial spectra for the geopotential-caused
crossover effects, discriminate these source-differences sharply. Thus, the zero-order LLC in DSC data contains zonal gravity
information not present in SSC data. In addition, zero- and first-order LLC of DSC data can reveal a geocenter discrepancy
between the orbit tracking of the separate satellite missions. For example, DSC analysis from orbits computed with JGM 2 show
that the y-axis of the geocenter for Geosat in 1986–1988 is shifted with respect to T/P by 6–9 cm towards the eastern Pacific. Also,
where the time-gap is necessarily large (as between, say, Geosat and T/P missions) oceanographic (sea-level) differences in
DSC may corrupt the geopotential interpretation of the data. Most importantly, as we illustrate, media delays for the altimeter
(from the ionosphere, wet troposphere and sea-state bias) are more likely sources of contamination across two missions than
in SSC analyses. Again, the LLC of zero order best shows this contrast. Using the higher-order LLC of DSC for both Geosat-T/P
and ERS 1-T/P as likely representation of geopotential-only error, we show by comparison with the predicted standard errors
of JGM 2 that the latter's previously calibrated covariance matrix is generally valid.
Received: 14 February 1996 / Accepted: 27 March 1997 相似文献
6.
TOPEX/Poseidon orbit error assessment 总被引：1，自引：0，他引：1
A. J. E. Smith E. T. Hesper D. C. Kuijper G. J. Mets P. N. A. M. Visser B. A. C. Ambrosius K. F. Wakker 《Journal of Geodesy》1996,70(9):546-553
This paper discusses the accuracy of TOPEX/Poseidon orbits computed at Delft University, Section Space Research & Technology (DUT/SSR&T), from several types of tracking data,i.e. SLR, DORIS, and GPS. To quantify the orbit error, three schemes are presented. The first scheme relies on the direct altimeter observations and the covariance of the JGM-2 gravity field. The second scheme is based on crossover difference residuals while the third scheme uses the differences of dynamic orbit solutions with the GPS reduced-dynamic orbit. All three schemes give comparable results and indicate that the radial orbit error of TOPEX/Poseidon is 3–4 cm. From the orbit comparisons with GPS reduced dynamic, both the along-track and cross-track errors of the dynamic orbit solutions were found to be within 10–15 cm. 相似文献
7.
ERS-1 radial positioning using the JGM-2 and JGM-3 gravity fields is assessed by analysing dual crossovers with TOPEX/Poseidon,
neither field containing ERS-1 data. This method allows a more complete recovery of ERS-1 radial orbit error, specifically
of the previously unattainable mean geographical error. The global analysis shows that the theoretical error derived from
the JGM-2 covariance matrix is realistic and that JGM-3 represents a slight improvement, at least at the inclination of ERS-1.
A latitudinal-based study in the southern ocean indicates possible weaknesses in both fields, notably for low and resonant
geopotential orders m. A refinement of JGM-2, RGM-2, is undertaken through inclusion of ERS-1 and STELLA laser tracking and ERS-1 altimetry, reducing
several of its deficiencies.
Received: 14 May 1996 / Accepted: 17 February 1997 相似文献
8.
J. Klokočník Ch. Reigber P. Schwintzer C. A. Wagner J. Kostelecký 《Journal of Geodesy》2002,76(4):189-198
The new GFZ/GRGS gravity field models GRIM5-S1 and GRIM5-C1, currently used as initial models for the CHAMP mission, have
been compared with other recent models (JGM 3, EGM 96) for radial orbit accuracy (by means of latitude lumped coefficients)
in computations on altimetry satellite orbits. The bases for accuracy judgements are multi-year averages of crossover sea
height differences from Geosat and ERS 1/2 missions. This radially sensitive data is fully independent of the data used to
develop these gravity models. There is good agreement between the observed differences in all of the world's oceans and projections
of the same errors from the scaled covariance matrix of their harmonic geopotential coefficients. It was found that the tentative
scale factor of five for the formal standard deviations of the harmonic coefficients of the new GRIM fields is justified,
i.e. the accuracy estimates, provided together with the GRIM geopotential coefficients, are realistic.
Received: 20 February 2001 / Accepted: 24 October 2001 相似文献
9.
精密轨道确定在深空探测中至关重要,而定轨数据中的白噪声会影响定轨性能。基于零相位分析,比较了FRR（forward-filter reverse-filter reverse-output）、RRF（reverse-filter reverse-filter forward-output）和Matlab中的filtfilt这3种滤波器的优劣,设计了一种零相位Kaiser窗低通滤波器。利用火星快车号（Mars Express,MEX）的仿真数据和实测数据验证了零相位Kaiser窗低通滤波器的性能,结果发现滤除白噪声后MEX数据的定轨精度有了显著改善。双程测速数据残差均方根（root mean square,RMS）减小为原来的1/3左右,达到了0.031 mm/s;轨道位置和速度与欧空局（European Space Agency,ESA）精密轨道的差异明显变小。该滤波算法作为定轨前的数据预处理可以提高定轨精度,从而为中国火星探测器的轨道数据处理提供一定的参考。 相似文献
10.
The single- and dual-satellite crossover (SSC and DSC) residuals between and among Geosat, TOPEX/Poseidon (T/P), and ERS
1 or 2 have been used for various purposes, applied in geodesy for gravity field accuracy assessments and determination as
well as in oceanography. The theory is presented and various examples are given of certain combinations of SSC and DSC that test for residual altimetry data errors, mostly of non-gravitational origin, of the order of a few centimeters.
There are four types of basic DSCs and 12 independent combinations of them in pairs which have been found useful in the present
work. These are defined in terms of the `mean' and `variable' components of a satellite's geopotential orbit error from Rosborough's
1st-order analytical theory. The remaining small errors, after all altimeter data corrections are applied and the relative
offset of coordinate frames between altimetry missions removed, are statistically evaluated by means of the Student distribution.
The remaining signal of `non-gravitational' origin can in some cases be attributed to the main ocean currents which were not
accounted for among the media or sea-surface corrections. In future, they may be resolved by a long-term global circulation
model. Experience with two current models, neither of which are found either to cover the most critical missions (Geosat &
TOPEX/Poseidon) or to have the accuracy and resolution necessary to account for the strongest anomalies found across them,
is described. In other cases, the residual signal is due to errors in tides, altimeter delay corrections or El Ni?o. (Various
examples of these are also presented.) Tests of the combinations of the JGM 3-based DSC residuals show that overall the long-term
data now available are well suited for a gravity field inversion refining JGM 3 for low- and resonant-order geopotential harmonics
whose signatures are clearly seen in the basic DSC and SSC sets.
Received: 15 January 1999 / Accepted: 9 September 1999 相似文献
11.
This analysis was performed with the GEOSAT software developed at NDRE for high-precision analysis of satellite tracking and VLBI data for geodetic and geodynamic applications.For applications to ERS-1, a realistic surface force model is used together with the Jacchia 77 atmospheric model, semi-daily drag coefficients, a 1-cpr sinusoidal along-track acceleration, and the GSFC JGM-2 gravity model. ERS-1 orbits have been derived for 5.5-day arcs of laser tracking data between July 6 and August 12, 1992. Results from overlapping orbits and comparison with precise D-PAF orbits indicate an orbital accuracy of 10–15 cm in the radial direction, ~ 60 cm in the along-track direction and ~ 15 cm in the cross-track direction. 相似文献
12.
13.
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
14.
低阶地球引力场长期变化的确定 总被引：3，自引：1，他引：2
利用约11年的Lageos人卫激光测距（SLR）资料,反演了地球引力场系数J2和J3变化的时间序列,分析得到每年的2＝(-2.6±0.4)×10-11,3＝(-1.2±0.4)×10-11及18.6年固体潮Love数k2=0.3154±0.0070,相位滞后ε=3.1°±2.0°.由此可以对地幔滞弹和地球各圈层的动力学变化及相互作用提供高精度的天文观测约束。为了提供高精度的J2和J3变化的时间序列,可能的误差源必须考虑,如自转速率变化引起的极潮,引力场系数Jn的低阶和高阶项之间的弱的耦合等。 相似文献
15.
One-year average satellite altimetry data from the Exact Repeat Missions (ERM) of GEOSAT have been used to determine marine gravity disturbances in the Labrador Sea region using the inverse Hotine approach with FFT techniques. The derived satellite gravity information has been compared to shipboard gravity as well as gravity information derived by least-squares collocation (LSC), GEMT3 and OSU91A geopotential models in the Orphan Knoll area. The RMS and mean differences between satellite and shipboard gravity disturbances are about 8.0 and 2.8 mGal, respectively. There is no significantly difference between the results obtained using FFT and LSC. 相似文献
16.
导航解算中的系统误差及其协方差矩阵拟合 总被引：17，自引：2，他引：17
利用Kslman滤波进行导航定位计算不得不涉及观测函数模型和动力学模型,而观测函数模型和动力学模型经常含有系统误差或区域性系统误差.本文提出了一种基于移动窗口的函数模型和随机模型系统误差自适应拟合法.基于相同的窗口给出了相应的观测向量和状态预测向量的协方差矩阵估计方法,其协方差矩阵的估计与现有的Sage滤波不同.利用经系统误差修正后的观测向量和状态预测向量及相应的协方差矩阵,再进行动态导航滤波计算,能有效提高导航解的精度.文中给出了开窗估计系统误差的公式,并利用实测数据验证了该算法的可行性和实用性.计算结果表明该算法能有效地抵制系统误差对导航滤波结果的影响. 相似文献
17.
A technique is presented for the development of a high-precision and high-resolution mean sea surface model utilising radar
altimetric sea surface heights extracted from the geodetic phase of the European Space Agency (ESA) ERS-1 mission. The methodology
uses a cubic-spline fit of dual ERS-1 and TOPEX crossovers for the minimisation of radial orbit error. Fourier domain processing
techniques are used for spectral optimal interpolation of the mean sea surface in order to reduce residual errors within the
initial model. The EGM96 gravity field and sea surface topography models are used as reference fields as part of the determination
of spectral components required for the optimal interpolation algorithm. A comparison between the final model and 10 cycles
of TOPEX sea surface heights shows differences of between 12.3 and 13.8 cm root mean square (RMS). An un-optimally interpolated
surface comparison with TOPEX data gave differences of between 15.7 and 16.2 cm RMS. The methodology results in an approximately
10-cm improvement in accuracy. Further improvement will be attained with the inclusion of stacked altimetry from both current
and future missions.
Received: 22 December 1999 / Accepted: 6 November 2000 相似文献
18.
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
19.
研究了绕月卫星自主导航方法,提出了由星敏感器、紫外月球敏感器和测高仪组成的多源信息组合导航方案。将Unscented Kalman滤波(UKF)应用于非线性导航系统,采用信息融合技术设计了相关的联邦滤波算法,实现了系统的信息互补,完成了卫星轨道的最优估计。利用数学仿真对这种导航系统的有效性进行了验证,并与基于扩展Kal man滤波(EKF)的信息融合算法进行了比较。仿真结果表明,所提出的UKF融合算法具有良好的稳定性,可进一步提高导航系统的精度。 相似文献
20.
粗／精轨道数据对卫星InSAR DEM精度影响的对比分析 总被引：2，自引：0，他引：2
本文在介绍InSAR系统中卫星轨道状态矢量内插方法的基础上，从理论和实际两方面分析了轨道数据误差对参考椭球面相位、地形干涉相位和数字高程模型（DEM）精度的影响。以上海局部地区作为实验场，采用ERS-1／2卫星SAR影像数据，分别使用欧洲空间局粗略轨道数据和荷兰Delft大学空间研究中心精密轨道数据进行了干涉处理，生成了两种情况下的DEM，并对相关精度进行了对比与分析。研究结果表明，使用精轨数据建立的DEM的精度明显高于基于粗轨数据建立的DEM的精度。 相似文献