共查询到20条相似文献，搜索用时 31 毫秒
1.
Since its launch in 2002, the Gravity Recovery and Climate Experiment (GRACE) mission has been providing measurements of the
time-varying Earth gravity field. The GRACE mission architecture includes two satellites in near-circular, near-polar orbits
separated in the along-track direction by approximately 220 km (e.g. collinear). A microwave ranging instrument measures changes
in the distance between the spacecraft, while accelerometers on each spacecraft are used to measure changes in distance due
to non-gravitational forces. The fact that the satellites are in near-polar orbits coupled with the fact that the inter-satellite
range measurements are directed in the along-track direction, contributes to longitudinal striping in the estimated gravity
fields. This paper examines four candidate mission architectures for a future gravity recovery satellite mission to assess
their potential in measuring the gravity field more accurately than GRACE. All satellites were assumed to have an improved
measurement system, with an inter-satellite laser ranging instrument and a drag-free system for removal of non-gravitational
accelerations. Four formations were studied: a two-satellite collinear pair similar to GRACE; a four-satellite architecture
with two collinear pairs; a two-satellite cartwheel formation; and a four-satellite cartwheel formation. A cartwheel formation
consists of satellites performing in-plane, relative elliptical motion about their geometric center, so that inter-satellite
measurements are, at times, directed radially (e.g. parallel to the direction towards the center of the Earth) rather than
along-track. Radial measurements, unlike along-track measurements, have equal sensitivity to mass distribution in all directions
along the Earth’s surface and can lead to higher spatial resolution in the derived gravity field. The ability of each architecture
to recover the gravity field was evaluated using numerical simulations performed with JPL’s GIPSY-OASIS software package.
Thirty days of data were used to estimate gravity fields complete to degree and order 60. Evaluations were done for 250 and
400 km nominal orbit altitudes. The sensitivity of the recovered gravity field to under-sampled effects was assessed using
simulated errors in atmospheric/ocean dealiasing (AOD) models. Results showed the gravity field errors associated with the
four-satellite cartwheel formation were approximately one order of magnitude lower than the collinear satellite pair when
only measurement system errors were included. When short-period AOD model errors were introduced, the gravity field errors
for each formation were approximately the same. The cartwheel formations eliminated most of the longitudinal striping seen
in the gravity field errors. A covariance analysis showed the error spectrum of the cartwheel formations to be lower and more
isotropic than that of the collinear formations. 相似文献
2.
Pavel Ditmar Jo?o Teixeira da Encarna??o Hassan Hashemi Farahani 《Journal of Geodesy》2012,86(6):441-465
Spectral analysis of data noise is performed in the context of gravity field recovery from inter-satellite ranging measurements acquired by the satellite gravimetry mission GRACE. The motivation of the study is two-fold: (i) to promote a further improvement of GRACE data processing techniques and (ii) to assist designing GRACE follow-on missions. The analyzed noise realizations are produced as the difference between the actual GRACE inter-satellite range measurements and the predictions based on state-of-the-art force models. The exploited functional model is based on the so-called “range combinations,” which can be understood as a finite-difference analog of inter-satellite accelerations projected onto the line-of-sight connecting the satellites. It is shown that low-frequency noise is caused by limited accuracy of the computed GRACE orbits. In the first instance, it leads to an inaccurate estimation of the radial component of the inter-satellite velocities. A large impact of this component stems from the fact that it is directly related to centrifugal accelerations, which have to be taken into account when the measured range-accelerations are linked with inter-satellite accelerations. Another effect of orbit inaccuracies is a miscalculation of forces acting on the satellites (particularly, the one described by the zero-degree term of the Earth’s gravitational field). The major contributors to the noise budget at high frequencies (above 9?mHz) are (i) ranging sensor errors and (ii) limited knowledge of the Earth’s static gravity field at high degrees. Importantly, we show that updating the model of the static field on the basis of the available data must be performed with a caution as the result may not be physical due to a non-unique recovery of high-degree coefficients. The source of noise in the range of intermediate frequencies (1–9?mHz), which is particularly critical for an accurate gravity field recovery, is not fully understood yet. We show, however, that it cannot be explained by inaccuracies in background models of time-varying gravity field. It is stressed that most of the obtained results can be treated as sufficiently general (i.e., applicable in the context of a statistically optimal estimation based on any functional model). 相似文献
3.
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
4.
G. M. Appleby 《Journal of Geodesy》1998,72(6):333-342
In this paper we describe the results of an analysis of a 2.5-year set of satellite laser range observations of the two Etalon
geodetic satellites. We fit continuous orbits to the range observations, and map the range residuals into series of equivalent
orbital element residuals, considering in detail the orbital longitude, eccentricity and nodal residuals. We use the longitude
residuals to study thermal effects acting on the satellites and compare the results with those published for the Lageos satellites.
We discuss the differences between the two series of eccentricity residuals, and again compare the results with those from
Lageos. Finally we use the nodal residuals to investigate the potential for determination of UT1 of the reference frame defined
by the orbits of the Etalon satellites.
Received: 30 January 1997 / Accepted: 11 December 1997 相似文献
5.
Starting from the analytical theory of perturbed␣circular motions presented in Celestial Mechanics (Bois 1994) and from specific
extended formulations of the perturbations in a uniformly rotating plane of constant inclination, this paper presents an extended
formulation of the solution. The actual gain made through this extension is the establishment of a first-order predictive
theory written in spherical coordinates and thus free of singularities, whose perturbations are directly expressed in the
local orbital frame generally used in satellite geodesy. This new formulation improves the generality, the precision and the
field of applications of the theory. It is particularly devoted to the analysis of satellite position perturbations for satellites
in low eccentricity orbits usually used for many Earth observation applications. An application to the TOPEX/Poseidon (T/P)
orbit is performed. In particular, contour maps are provided which show the geographical location of orbit differences coming
from geopotential coefficient differences of two recent gravity field models. Comparison of predicted radial and along-track
orbit differences with respect to numerical results provided by the French group (CNES, in Toulouse) in charge of the T/P
orbit are convincing.
Received 22 January 1996; Accepted 19 September 1996 相似文献
6.
Frequency-dependent data weighting in global gravity field modeling from satellite data contaminated by non-stationary noise 总被引：1，自引：0，他引：1
Satellite data that are used to model the global gravity field of the Earth are typically corrupted by correlated noise, which
can be related to a frequency dependence of the data accuracy. We show an opportunity to take such noise into account by using
a proper noise covariance matrix in the estimation procedure. If the dependence of noise on frequency is not known a priori,
it can be estimated on the basis of a posteriori residuals. The methodology can be applied to data with gaps. Non-stationarity
of noise can also be dealt with, provided that the necessary a priori information exists. The proposed methodology is illustrated
with CHAllenging Mini-satellite Payload (CHAMP) data processing. It is shown, in particular, that the usage of a proper noise
model can make the measurements of non-gravitational satellite accelerations unnecessarily. This opens the door for high-quality
modeling of the Earth’s gravity field on the basis of observed orbits of non-dedicated satellites (i.e., satellites without
an on-board accelerometer). Furthermore, the processing of data from dedicated satellite missions – GRACE (Gravity Recovery
and Climate Experiment) and GOCE (Gravity field and steady-state Ocean Circulation Explorer) – may also benefit from the proposed
methodology. 相似文献
7.
8.
月球重力场模型研究进展和我国将来月球卫星重力梯度计划实施 总被引：4，自引：0，他引：4
本文介绍了基于国际探月观测数据建立的月球重力场模型:8×4、15×8、13×13、5×5、7×7、16×16-1/2/3、Lun60d、GLGM-1/2、LP75D/G、LP100K/J、LP165P、LP150Q和SGM90d;通过对比SST-HL/LL-Doppler-VLBI和SST-HL/SGG-Doppler-VLBI跟踪观测模式的优缺点,建议我国将来首期月球卫星重力测量计划采用SST-HL/SGG-Doppler-VLBI较优;其次,通过对比静电悬浮、超导和量子卫星重力梯度仪的优缺点,建议我国将来首期月球卫星重力梯度计划采用静电悬浮重力梯度仪;并建议我国将来首颗月球重力梯度卫星的轨道高度(50～100 km)选择在已有月球探测卫星的测量盲区,轨道倾角(90°±3°)设计为有利于月球卫星观测数据全球覆盖的近极轨模式。 相似文献
9.
The performance of the L-curve criterion and of the generalized cross-validation (GCV) method for the Tikhonov regularization
of the ill-conditioned normal equations associated with the determination of the gravity field from satellite gravity gradiometry
is investigated. Special attention is devoted to the computation of the corner point of the L-curve, to the numerically efficient
computation of the trace term in the GCV target function, and to the choice of the norm of the residuals, which is important
for the Gravity Field and Steady-State Ocean Circulation Explorer (GOCE) in the presence of colored observation noise. The
trace term in the GCV target function is estimated using an unbiased minimum-variance stochastic estimator. The performance
analysis is based on a simulation of gravity gradients along a 60-day repeat circular orbit and a gravity field recovery complete
up to degree and order 300. Randomized GCV yields the optimal regularization parameter in all the simulations if the colored
noise is properly taken into account. Moreover, it seems to be quite robust against the choice of the norm of the residuals.
It performs much better than the L-curve criterion, which always yields over-smooth solutions. The numerical costs for randomized
GCV are limited provided that a reasonable first guess of the regularization parameter can be found.
Received: 17 May 2001 / Accepted: 17 January 2002 相似文献
10.
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
11.
LUO Jia LUO Zhicai ZOU Xiancai WANG Haihong 《地球空间信息科学学报》2006,9(4):265-268
IntroductionThe high-accauary and high-resolution Earth’sgravity field can be recovered with satellite-to-satellite tracking (SST) technique , the preciseintersatellite tracking technique . The SSTtech-nique has been studied since 1960’s . The modesof S… 相似文献
12.
Parametric least squares collocation was used in order to study the detection of systematic errors of satellite gradiometer
data. For this purpose, simulated data sets with a priori known systematic errors were produced using ground gravity data
in the very smooth gravity field of the Canadian plains. Experiments carried out at different satellite altitudes showed that
the recovery of bias parameters from the gradiometer “measurements” is possible with high accuracy, especially in the case
of crossing tracks. The mean value of the differences (original minus estimated bias parameters) was relatively large compared
to the standard deviation of the corresponding second-order derivative component at the corresponding height. This mean value
almost vanished when gravity data at ground level were combined with the second-order derivative data set at satellite altitude.
In the case of simultaneous estimation of bias and tilt parameters from ∂2
T/∂z
2“measurements”, the recovery of both parameters agreed very well with the collocation error estimation.
Received: 10 October 1996 / Accepted 25 May 1998 相似文献
13.
Taking China as the region for test the potential of the new satellite gravity technique, satelliteto-satellite tracking for improving the accuracy of regional gravity field model is studied. With WDM94 as reference, the gravity anomaly residuals of three models, the latest two GRACE global gravity field model (EIGEN_GRACE02S, GGM02S) and EGM96, are computed and compared. The causes for the differences among the residuals of the three models are discussed. The comparison between the residuals shows that in the selected region, EIGEN_GRACE02S or GGM02S is better than EGM96 in lower degree part (less than 110 degree). Additionally, through the analysis of the model gravity anomaly residuals, it is found that some systematic errors with periodical properties exist in the higher degree part of EIGEN and GGM models, the results can also be taken as references in the validation of the SST gravity data. 相似文献
14.
Satellite gradiometry using a satellite pair 总被引：1，自引：1，他引：1
The GRACE mission has substantiated the low–low satellite-to-satellite tracking (LL-SST) concept. The LL-SST configuration can be combined with the previously realized high–low SST concept in the CHAMP mission to provide a much higher accuracy. The line of sight (LOS) acceleration difference between the GRACE satellite pair, the simplest form of the combined observable, is mostly used for mapping the global gravity field of the Earth in terms of spherical harmonic coefficients. As an alternative observable, a linear combination of the gravitational gradient tensor components is proposed. Being a one-point function and having a direct relation with the field geometry (curvature of the field at the point) are two noteworthy achievements of the alternative formulation. In addition, using an observation quantity that is related to the second-instead of the first-order derivatives of the gravitational potential amplifies the high-frequency part of the signal. Since the transition from the first- to the second-order derivatives includes the application of a finite-differences scheme, the high-frequency part of the noise is also amplified. Nevertheless, due to the different spectral behaviour of signal and noise, in the end the second-order approach leads to improved gravitational field resolution. Mathematical formulae for the gradiometry approach, for both linear and higher-degree approximations, are derived. The proposed approach is implemented for recovery of the global gravitational field and the results are compared with those of LOS acceleration differences. Moreover, LOS acceleration difference residuals are calculated, which are at the level of a few tenths of mGal. Error analysis shows that the residuals of the estimated degree variances are less than 10–3. Furthermore, the gravity anomaly residuals are less than 2 mGal for most points on the Earth. 相似文献
15.
中国区域SST卫星重力场模型精度分析 总被引：1，自引：0，他引：1
通过比较最新SST地球重力场模型EIGEN_GRACE02S、GGM02S和EGM96模型在中国区域与WDM94模型重力异常残差的差异，分析差异产生的原因及分布，研究新一代卫星重力方法对于提高区域重力场模型精度的潜力以及存在的问题。结果证明，卫星跟踪卫星方法对于现有模型中低阶部分有明显改善。 相似文献
16.
P. Schwintzer C. Reigber A. Bode Z. Kang S. Y. Zhu F.-H. Massmann J. C. Raimondo R. Biancale G. Balmino J. M. Lemoine B. Moynot J. C. Marty F. Barlier Y. Boudon 《Journal of Geodesy》1997,71(4):189-208
Summary. GFZ Potsdam and GRGS Toulouse/Grasse jointly developed a new pair of global models of the Earth's gravity field to satisfy
the requirements of the recent and future geodetic and altimeter satellite missions. A precise gravity model is a prerequisite
for precise satellite orbit restitution, tracking station positioning and altimeter data reduction. According to different
applications envisaged, the new model exists in two parallel versions: the first one being derived exclusively from satellite
tracking data acquired on 34 satellites, the second one further incorporating satellite altimeter data over the oceans and
terrestrial gravity data. The most recent “satellite-only” gravity model is labelled GRIM4-S4 and the “combined” gravity model
GRIM4-C4. The models are solutions in spherical harmonics and have a resolution up to degree and order 60 plus a few resonance
terms in the case of GRIM4-S4, and up to degree/order 72 in the case of GRIM4-C4, corresponding to a spatial resolution of
555 km at the Earth's surface. The gravitational coefficients were estimated in a rigorous least squares adjustment simultaneously
with ocean tidal terms and tracking station position parameters, so that each gravity model is associated with a consistent
ocean tide model and a terrestrial reference frame built up by over 300 optical, laser and Doppler tracking stations. Comprehensive
quality tests with external data and models, and test arc computations over a wide range of satellites have demonstrated the
state-of-the-art capabilities of both solutions in long-wavelength geoid representation and in precise orbit computation.
Received 1 February 1996; Accepted 17 July 1996 相似文献
17.
Design considerations for a dedicated gravity recovery satellite mission consisting of two pairs of satellites 总被引：5，自引：0，他引：5
Future satellite missions dedicated to measuring time-variable gravity will need to address the concern of temporal aliasing
errors; i.e., errors due to high-frequency mass variations. These errors have been shown to be a limiting error source for
future missions with improved sensors. One method of reducing them is to fly multiple satellite pairs, thus increasing the
sampling frequency of the mission. While one could imagine a system architecture consisting of dozens of satellite pairs,
this paper explores the more economically feasible option of optimizing the orbits of two pairs of satellites. While the search
space for this problem is infinite by nature, steps have been made to reduce it via proper assumptions regarding some parameters
and a large number of numerical simulations exploring appropriate ranges for other parameters. A search space originally consisting
of 15 variables is reduced to two variables with the utmost impact on mission performance: the repeat period of both pairs
of satellites (shown to be near-optimal when they are equal to each other), as well as the inclination of one of the satellite
pairs (the other pair is assumed to be in a polar orbit). To arrive at this conclusion, we assume circular orbits, repeat
groundtracks for both pairs of satellites, a 100-km inter-satellite separation distance, and a minimum allowable operational
satellite altitude of 290 km based on a projected 10-year mission lifetime. Given the scientific objectives of determining
time-variable hydrology, ice mass variations, and ocean bottom pressure signals with higher spatial resolution, we find that
an optimal architecture consists of a polar pair of satellites coupled with a pair inclined at 72°, both in 13-day repeating
orbits. This architecture provides a 67% reduction in error over one pair of satellites, in addition to reducing the longitudinal
striping to such a level that minimal post-processing is required, permitting a substantial increase in the spatial resolution
of the gravity field products. It should be emphasized that given different sets of scientific objectives for the mission,
or a different minimum allowable satellite altitude, different architectures might be selected. 相似文献
18.
This study analyzes the quality of onboard data of tracking signals from GPS satellites on the far side of the earth and determines the orbit of the geostationary satellite using code and carrier phase observations with 30-h and 3-day orbit arc length. According to the analysis results, the onboard receiver can track 6–8 GPS satellites, and the minimum and maximum carrier to noise spectral densities were 24 and 45 dB-Hz, respectively. For a GPS receiver on a high-altitude platform above the navigation constellations, the blocking of the earth and a weak signal strength usually cause a piece-wise GPS signal tracking and an increase in the number of ambiguity parameters. Individual GPS satellites may be continuously tracked for as little as several minutes and as long as 3 h. Moreover, considering the negative sign of elevation angles reflects the fact that GPS satellites are tracked below the receiver in the study. GPS satellites appear mainly in the elevation angle range of ??53° to ??83°, and dilution of precision values could reach ten or one hundred and more. Also, it is observed that when a signal suffers from atmospheric refraction, other GPS signals tracked simultaneously by the receiver experience strong systematic errors in the code observations. Based on single-frequency code and carrier phase measurements, the mean 3D root mean square (RMS) value of the overlap comparisons between 30-h orbit determination arcs is 2.14 m. However, we found that there were also some biases in the carrier phase residuals, which contributed to poor orbit accuracy. To eliminate the effects of the biases, we established a correction sequence for each GPS satellite. After corrections, the mean 3D RMS was reduced to 0.99 m, representing a 53% improvement. 相似文献
19.
20.
Space-wise approach to satellite gravity field determination in the presence of coloured noise 总被引：2，自引：2，他引：2
For many years, the gravity field of the Earth was only seen by satellite geodesy as the main factor affecting the orbit and consequently it was retrieved together with a number of other orbital perturbations. Since the advent of a new generation of accelerometers, non-gravitational perturbations can be separated from the gravity effects and a new era of gravity field estimates from space has been born. During preparatory data analysis for new missions performed by the geodetic community, three approaches have been proposed and numerically tested: the brute force method (direct approach), the semi-analytical (time-wise) method and the space-wise method. In particular, the time-wise method takes advantage of the incoming time flow of data and, after performing a Fourier transform of the observation equations, exploits the prevailing block diagonal structure of the normal equations to estimate the spherical harmonic coefficients of the gravity field. Complementary to this is the space-wise approach, which goes back to the traditional computation of the harmonic coefficients by an integration technique or by least-squares collocation. Some advantages and disadvantages are peculiar to both methods, particularly the space-wise approach, which has for a long time ignored the marked signature of the noise spectrum due to the specific measuring conditions of space-borne accelerometers. The application of a proper Wiener filter, exploiting the correlation along the orbit, embedded into an iterative scheme, seems to be the answer. The solution to this major problem of the space-wise approach is illustrated and simulation results are discussed. 相似文献