以下两篇参考文献的第一作者均为华裔学者程敏康。其一关注的是地球重力场的长期变化，其二是地球重力场低阶球谐系数偶数项的季节变化。

前者使用了20年的Starlette, LAGEOS 1 and 2, Ajisai, Etalon 1 and 2, Stella, and BE-C卫星的激光观测数据。

后者使用了1993到1996年的地球动力学卫星Starlette, Ajisai, Stella, LAGEOS I and LAGEOS II的激光观测数据。

美国德克萨斯大学空间研究中心的程敏康曾经与我院进行合作研究，并于去年9月就卫星激光测距的重力场应用主题做了学术报告。

 

参考文献及其摘要：

Determination of long-term changes in the Earth's gravity field from satellite laser ranging observations

Auteur(s) / Author(s)

CHENG M. K. ⁽¹⁾ ; SHUM C. K. ⁽¹⁾ ; TAPLEY B. D. ⁽¹⁾ ;

Affiliation(s) du ou des auteurs / Author(s) Affiliation(s)

⁽¹⁾ Center for Space Research, University of Texas at Austin, ETATS-UNIS

Résumé / Abstract

Temporal changes in the Earth's gravity field have been determined by analyzing satellite laser ranging (SLR) observations of eight geodetic satellites using data spanning an interval of over 20 years. The satellites used in the analysis include Starlette, LAGEOS 1 and 2, Ajisai, Etalon 1 and 2, Stella, and BE-C. Geophysical parameters, related to both secular and long-period variations in the Earth's gravity field, including the geopotential zonal rates (J₂, J₃, J₄, J₅, and J₆) and the 18.6-year tide parameter, were estimated. The estimated values for these parameters are J₂ = -2.7±0.4(10^-11/yr); J₃ = -1.3±0.5(10^-11/yr); J₄ =-1.4±1.0(10^-11/yr); J₅ = 2.1±0.6(10^-11/yr); J₆ = 0.3±0.7(10^-11/yr); C⁺²⁰_18.6 = 1.56 ±0.2 (centimeters) and S⁺²⁰_18.6 = -0.1±0.2 (centimeters). The amplitude and phase for the 18.6-year tide are in general agreement with the effects predicted by the Earth's mantle anelasticity. The solution accuracy was evaluated by considering the effects of errors in various non-estimated dynamical model parameters and by varying the data span and data sets used in the solution. Estimates for J₃ from individual LAGEOS I and Starlette SLR data sets are in good agreement. The lumped sum values for J₃ and J₅ are very different for LAGEOS I and Starlette. The zonal rate determination is limited to degree 6 with the current SLR data sets. Analysis of the sensitivity of the solution for the zonal rates to the satellite tracking data span suggests that the temporal extension of the current SLR data sets will enhance the solution of zonal rates beyond degree 6.

 

Journal of geophysical research   ISSN 0148-0227 

1997, vol. 102,, pp. 22377-22390

 

 

JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 104, NO. B2, PAGES 2667–2681, 1999

Seasonal variations in low degree zonal harmonics of the Earth's gravity field from satellite laser ranging observations

Minkang Cheng

Center for Space Research, University of Texas at Austin

 

Byron D. Tapley

Center for Space Research, University of Texas at Austin

 

Abstract

Seasonal variations in the Earth's gravity field were determined using satellite laser ranging (SLR) observations from multisatellite. The time series for the variations of the even zonal harmonics, J_l (l = 2, 4, 6, and 8), were determined using the SLR data from the geodetic satellites, including Starlette, Ajisai, Stella, LAGEOS I and LAGEOS II, during the period from October 1993 to December 1996. Owing to uncertainties in the eccentricity excitation for LAGEOS I and II, the variations of J ₃ and J ₅ were determined using only the SLR data from Starlette, Ajisai, and Stella. The seasonal variations of J ₂, J ₄, J ₆ and J ₈ become separable using the existing multisatellite SLR data sets collected in 15-day time intervals. The amplitude (normalized and in units of 10⁻¹⁰) and phase (in a cosine conversion and in units of degrees) for the annual variation in J_l (l= 2, 3, 4, 5, 6, and 8) are estimated to be (1.25 ± 0.1, 140 ± 10), (2.16 ± 0.21, 341 ± 19), (1.07 ± 0.1, 338 ± 15), (1.12 ± 0.16, 152 ± 16), (0.26 ± 0.17, 337 ± 9), and (1.03 ± .016, 209 ± 10), respectively. The observed annual variations of J ₃ and J ₅ are essentially opposite in phase. This phenomenon results in a different lumped sum effect for various satellites. For example, the lumped sum of J ₃ and J ₅ annual variation from LAGEOS I is twice as large as that from Starlette. The excitation due to the mass redistribution in the atmosphere and ocean and the changes in continental water storage were considered in this study using the available global geophysical data, which included the European Centre for Medium-Rang Weather Forecasts atmospheric surface pressure, the TOPEX/Poseidon altimetry derived sea surface anomalies, and the World Monthly Surface Station Climatic Data. Overall, the variation in the even zonal coefficients due to the atmospheric mass redistribution is responsible for 30% to 60% of the observed annual variations in the node residual for Starlette and LAGEOS I. Comparison indicates that the oceanic mass movement, in particular, the continental water change produce comparable contributions to the seasonal zonal variations. The amplitude of the observed annual variation of J ₂ is found to fall between the values predicted from the models of the surface water, ocean, and atmosphere with and without the inverted barometer (IB) oceanic response, but the phase is in good agreement with the IB models. The nontidal mass redistributions in atmosphere, ocean, and continental water change can only account for ∼13% of the semiannual variation in J ₂ but are the primary excitation sources for semiannual variations in the higher-degree zonal terms.

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