Improved Procedures for the Recovery of 5 degrees Mean Gravity Anomalies from ATS-6/GEOS-3 Satellite to Satellite Range-Rate Observations Using Least Squares Collocation,

Abstract
The prediction of 5 deg mean gravity anomalies is considered by collocation from ATS-6/GEOS-3 satellite to satellite range-rate observations. The auto and cross-covariances of the residual line of sight accelerations R-double dot from GEOS-3 to ATS-6 are computed rigorously in the anomalous potential field. The raw residual range-rate R-dot values are filtered and smoothed by approximating them in a least squares sense by a cubic spline function, and the residual accelerations R-double dot are obtained as the first derivatives of the spline. Experiments are described to fit the raw R-dot values by a spline function with variable knots, and to remove any linear trend from R-double dot values due to residual errors in initial state vectors. The correlation coefficients between the predicted values of neighboring anomalies are considered. Inspite of low density of range-rate data directly over the anomalies, and the high noise level of the destruct-doppler data, it appears that 5 deg anomalies can be predicted with a standard deviation of 6 mgals. It is found that these predicted anomalies agree much better with the altimeter anomalies than the anomalies implied by PGS 110 field.

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