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71.
利用卫星测高、GRACE和GOCE资料估计全球海洋表面地转流 总被引：1，自引：1，他引：0
重力恢复和气候试验GRACE(gravity recovery and climate experiment)卫星极大地提高了地球重力场的精度和分辨率,特别是中长波分量,联合卫星测高数据可获得全球海洋表面大尺度洋流循环。另外,新一代地球重力和海洋环流探测卫星GOCE(gravity field and steady-state ocean circulation explorer)于2009年3月成功发射,采用卫星重力梯度测量原理,对重力场的高频部分非常敏感,使其高分辨率监测全球海洋循环成为可能。本文利用1~7年GRACE观测数据确定的重力场模型和18个月GOCE观测数据确定的地球重力场模型GO_CONS_GCF_2_TIM_R3,联合卫星测高确定的平均海面高模型MSS_CNES_CLS_11,分别估计全球海洋表面地转流,并且与实测浮标数据结果进行比较。分析表明GOCE重力卫星确定的重力场模型具有更高的空间分辨率,能够确定高精度和高空间分辨率的全球海洋地转流,如墨西哥湾暖流的细节和特征,并且与实测浮标结果基本一致。而基于1~4年GRACE观测资料的模型不能很好估计全球地转流特征,基于7年GRACE观测资料的重力场模型ITG-Grace2010s确定的全球地转流的精度仍低于18个月GOCE观测数据确定的地球重力场模型GO_CONS_GCF_2_TIM_R3的结果,估计的全球地转流仍含有较大的噪声,不能很好地反应中小尺度地转流细节特征。并计算ITG_Grace2010s和GOCE_TIM3的稳态海面地形和全球平均地转流的内符合精度,结果显示,在全球范围内,GOCE_TIM3的稳态海面地形和全球平均地转流的精度都比ITG_Grace2010s结果的精度有着很大的改善,其中ITG_Grace2010s的稳态海面地形的精度为21.6cm,而GOCE_TIM3的结果则为7.45cm,ITG_Grace2010s的全球平均地转流的精度为40.7cm/s,而GOCE_TIM3的结果则为19.6cm/s。 相似文献
72.
Non-Singular Expressions for the Gravity Gradients in the Local North-Oriented and Orbital Reference Frames 总被引：4，自引：3，他引：1
The conventional expansions of the gravity gradients in the local north-oriented reference frame have a complicated form, depending on the first- and second-order derivatives of the associated Legendre functions of the colatitude and containing factors which tend to infinity when approaching the poles. In the present paper, the general term of each of these series is transformed to a product of a geopotential coefficient and a sum of several adjacent Legendre functions of the colatitude multiplied by a function of the longitude. These transformations are performed on the basis of relations between the Legendre functions and their derivatives published by Ilk (1983). The second-order geopotential derivatives corresponding to the local orbital reference frame are presented as linear functions of the north-oriented gravity gradients. The new expansions for the latter are substituted into these functions. As a result, the orbital derivatives are also presented as series depending on the geopotential coefficients multiplied by sums of the Legendre functions whose coefficients depend on the longitude and the satellite track azimuth at an observation point. The derived expansions of the observables can be applied for constructing a geopotential model from the GOCE mission data by the time-wise and space-wise approaches. The numerical experiments demonstrate the correctness of the analytical formulas.An erratum to this article can be found at 相似文献
73.
重力卫星和测高卫星五年来的进展 总被引：4，自引：4，他引：0
对近年升空的重力卫星CHAMP和GRACE及将于近期升空的GOCE卫星,以及测高卫星ENVISAT,Jason1,GFO,ICESat和CryoSat的技术特点进行了介绍和评估。 相似文献
74.
利用GOCE卫星轨道反演地球重力场模型 总被引：1，自引：1，他引：0
根据积分方程法反演地球重力场的数学模型,利用GOCE卫星2009-11-02～2010-01-02共61d的精密轨道数据反演了几组地球重力场模型。结果表明,GOCE卫星轨道能有效提取地球重力场的长波信息,弥补了GOCE卫星重力梯度带宽的限制,在106阶次的大地水准面误差为±9.6cm,该阶次精度优于EIGEN-CHAMP03S及GRACE卫星两个月轨道反演地球重力场的精度,但由于两极空白,反演的带谐位系数精度偏低。联合GOCE及GRACE卫星轨道反演的模型在106阶次的大地水准面误差为±6.9cm,弥补了GOCE卫星轨道的缺陷。 相似文献
75.
Computation of spherical harmonic coefficients from gravity gradiometry data to be acquired by the GOCE satellite: regularization issues 总被引：1，自引：0，他引：1
The issue of optimal regularization is investigated in the context of the processing of satellite gravity gradiometry (SGG) data that will be acquired by the GOCE (Gravity Field and Steady-State Ocean Circulation Explorer) satellite. These data are considered as the input for determination of the Earths gravity field in the form of a series of spherical harmonics. Exploitation of a recently developed fast processing algorithm allowed a very realistic setup of the numerical experiments to be specified, in particular: a non-repeat orbit; 1-s sampling rate; half-year duration of data series; and maximum degree and order set to 300. The first goal of the study is to compare different regularization techniques (regularization matrices). The conclusion is that the first-order Tikhonov regularization matrix (the elements are practically proportional to the degree squared) and the Kaula regularization matrix (the elements are proportional to the fourth power of the degree) are somewhat superior to other regularization techniques. The second goal is to assess the generalized cross-validation method for the selection of the regularization parameter. The inference is that the regularization parameter found this way is very reasonable. The time expenditure required by the generalized cross-validation method remains modest even when a half-year set of SGG data is considered. The numerical study also allows conclusions to be drawn regarding the quality of the Earths gravity field model that can be obtained from the GOCE SGG data. In particular, it is shown that the cumulative geoid height error between degrees 31 and 200 will not exceed 1 cm.
AcknowledgmentsThe authors thank Dr. E. Schrama for valuable discussions and for computing the orbit used to generate the long data set. They are also grateful to Prof. Tscherning and two anonymous reviewers for numerous valuable remarks and suggestions. The orbit to generate the short data set was kindly provided by J. van den IJssel. Computing resources were provided by Stichting Nationale Computerfaciliteiten (NCF), grant SG-027. 相似文献
76.
GOCE Data Processing: The Spherical Cap Regularization Approach 总被引：3，自引：0，他引：3
Due to the sun-synchronous orbit of the satellite gravity gradiometry mission GOCE, the measurements will not be globally
available. As a consequence, using a set of base functions with global support such as spherical harmonics, the matrix of
normal equations tends to be ill-conditioned, leading to weakly determined low-order spherical harmonic coefficients. The
corresponding geopotential strongly oscillates at the poles.
Considering the special configuration of the GOCE mission, in order to stabilize the normal equations matrix, the Spherical
Cap Regularization Approach (SCRA) has been developed. In this approach the geopotential function at the poles is predescribed
by an analytical continuous function, which is defined solely in the spatially restricted polar regions. This function could
either be based on an existing gravity field model or, alternatively, a low-degree gravity field solution which is adjusted
from GOCE observations. Consequently the inversion process is stabilized.
The feasibility of the SCRA is evaluated based on a numerical closed-loop simulation, using a realistic GOCE mission scenario.
Compared with standard methods such as Kaula and Tikhonov regularization, the SCRA shows a considerably improved performance. 相似文献
77.
卫星重力研究:21世纪大地测量研究的新热点 总被引：1，自引：0，他引：1
卫星重力发射将大大改善人们对地球重力场的了解 ,最近一些年已经和将要发射的 CHAMP、GRACE及GOCE卫星将把现有静态中长波长部分重力场的精度提高 1- 2个量级 ,并提供长波部分重力场随时间变化的信息。本文对这一大地测量的新进展作了简单叙述 相似文献
78.
Topographic–isostatic masses represent an important source of gravity field information, especially in the high-frequency
band, even if the detailed mass-density distribution inside the topographic masses is unknown. If this information is used
within a remove-restore procedure, then the instability problems in downward continuation of gravity observations from aircraft
or satellite altitudes can be reduced. In this article, integral formulae are derived for determination of gravitational effects
of topographic–isostatic masses on the first- and second-order derivatives of the gravitational potential for three topographic–isostatic
models. The application of these formulas is useful for airborne gravimetry/gradiometry and satellite gravity gradiometry.
The formulas are presented in spherical approximation by separating the 3D integration in an analytical integration in the
radial direction and 2D integration over the mean sphere. Therefore, spherical volume elements can be considered as being
approximated by mass-lines located at the centre of the discretization compartments (the mass of the tesseroid is condensed
mathematically along its vertical axis). The errors of this approximation are investigated for the second-order derivatives
of the topographic–isostatic gravitational potential in the vicinity of the Earth’s surface. The formulas are then applied
to various scenarios of airborne gravimetry/gradiometry and satellite gradiometry. The components of the gravitational vector
at aircraft altitudes of 4 and 10 km have been determined, as well as the gravitational tensor components at a satellite altitude
of 250 km envisaged for the forthcoming GOCE (gravity field and steady-state ocean-circulation explorer) mission. The numerical
computations are based on digital elevation models with a 5-arc-minute resolution for satellite gravity gradiometry and 1-arc-minute
resolution for airborne gravity/gradiometry. 相似文献
79.
Exploring the possibilities for star-tracker assisted calibration of the six individual GOCE accelerometers 总被引：1，自引：0，他引：1
P. N. A. M. Visser 《Journal of Geodesy》2008,82(10):591-600
A method has been developed and tested for estimating calibration parameters for the six accelerometers on board the Gravity
field and steady-state Ocean Circulation Explorer (GOCE) from star tracker observations. These six accelerometers are part
of the gradiometer, which is the prime instrument on board GOCE. It will be shown that by taking appropriate combinations
of observations collected by the accelerometers, by modeling acceleration terms caused by gravity gradients from an a priori
low-degree spherical harmonic expansion, and by modeling rotational acceleration terms derived from star-tracker observations,
scale factors of each of the accelerometers can be estimated for each axis. Simulated observations from a so-called end-to-end
simulator were used to test the method. This end-to-end simulator includes a detailed model of the GOCE satellite, its instruments
and instrument errors, and its environment. Results of the tests indicate that scale factors of all six accelerometers can
be determined with an accuracy of around 0.01 for all components on a daily basis. 相似文献
80.
Sean L. Bruinsma Christoph Förste Sandrine Mulet Marie-Hélène Rio Oleg Abrikosov Jean-Charles Marty 《Marine Geodesy》2016,39(3-4):238-255
The impact of GOCE Satellite Gravity Gradiometer data on gravity field models was tested. All models were constructed with the same Laser Geodynamics Satellite (LAGEOS) and Gravity Recovery and Climate Experiment (GRACE) data, which were combined with one or two of the diagonal gravity gradient components for the entire GOCE mission (November 2009 to October 2013). The Stokes coefficients were estimated by solving large normal equation (NE) systems (i.e., the direct numerical approach). The models were evaluated through comparisons with the European Space Agency's (ESA) gravity field model DIR-R5, by GPS/Leveling, GOCE orbit determination, and geostrophic current evaluations. Among the single gradient models, only the model constructed with the vertical ZZ gradients gave good results that were in agreement with the formal errors. The model based only on XX gradients is the least accurate. The orbit results for all models are very close and confirm this finding. All models constructed with two diagonal gradient components are more accurate than the ZZ-only model due to doubling the amount of data and having two complementary observation directions. This translates also to a slower increase of model errors with spatial resolution. The different evaluation methods cannot unambiguously identify the most accurate two-component model. They do not always agree, emphasizing the importance of evaluating models using many different methods. The XZ gravity gradient gives a small positive contribution to model accuracy. 相似文献