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  • 1
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    Preliminary solutions for the lunar gravity field from analysis of lunar orbiter tracking data (1994)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Knowledge of the gravitation field, in combination with surface topography, provides one of the principal means of inferring the internal structure of a planetary body. Previous analyses of the lunar gravitational field have been based on data from the Lunar Orbiters, the Apollo subsatellites, and the low altitude passes of the Apollo spacecraft. Recently, Konopliv et al. have reanalyzed all available Lunar Orbiter and Apollo subsatellite tracking data, producing a 60th degree and order solution. In preparation for the Clementine Mission to the Moon, we have also initiated a reanalysis of the Lunar Orbiter and Apollo subsatellite data. Our reanalysis takes advantage of advanced force and measurement modeling techniques as well as modern computational facilities. We applied the least squares collocation technique which stabilizes the behavior of the solution and high degree and order. The extension of the size of the field reduces the aliasing coming from the omitted portion of the gravitational field. This is especially important for the analysis of the tracking data from the Lunar Orbiters, as the periapse heights frequently ranged from 50 to 100 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., The Twenty-Fifth Lunar and Planetary Science Conference. Part 2: H-O; p 791-792
    Format: application/pdf
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  • 2
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    The Use of Mascons to Resolve Time-Variable Gravity from GRACE (2005)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We have analyzed GRACE Level 1B data to resolve time-variable gravity using a local mascon approach. The spherical harmonic solutions released to date resolve the signal from surface hydrology over land areas at spatial scales of 750 to 1000 km over one month intervals [Wahr et al., 2004; Tapley et al., 2004]. In our local approach, we solve explicitly for the mass of water in surface blocks using only the KBRR data collected as GRACE overflies the region of interest. The local representation of gravity minimizes leakage of errors from other areas due to aliasing or mismodelling. In this paper, we report on the analysis of GRACE data from January 2003 through August 2004 over three regions: the Amazon, the Indian subcontinent, and the continental United States. We solve for mass change at 10-day intervals using 4 deg x 4 deg blocks. We give an overview of our latest results, and we present the results of error analyses, and comparisons to both hydrology models and in-situ data.
    Keywords: Numerical Analysis
    Type: IAG Joint Assembly; Aug 22, 2005 - Aug 26, 2005; Cairns; Australia
    Format: text
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  • 3
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    Unique Approaches to Analysis of Time-Variable Gravity from GRACE (2004)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: We have developed an innovative analysis strategy for analysis of GRACE data. We have developed a capability to recover local/regional gravity changes using non-global functional representations (Le. surface anomalies vs. global spherical harmonics) h m the GRACE data. Our approach can take regularly or irregularly shaped regions, populate them with surface anomaly blocks of suitable area and solve for the resulting mass flux with respect to a mean field. The surface mass or gravity anomalies benefit from the application of spatial and temporal constraints to add stability to the solution. In this paper we discuss the analysis of four months of GRACE Level 1B data (accelerometry, intersatellite data, attitude information and precise orbits) from July to October 2003, recently released to the GRACE Science Team. We compare and contrast this local approach to gravity recovery, with the more conventional approach using global spherical harmonics. We review simulations of this technique which allow us to pinpoint optimum strategies for applications of this local gravity recovery approach.
    Keywords: Numerical Analysis
    Type: Joint CHAMP/GRACE Science Meeting; Jul 06, 2004 - Jul 08, 2004; Potsdam; Germany
    Format: text
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