A Comparison of Range and Range-Rate Measurements for the Generation of the GRACE Gravity Fields




Wallace, Mark S.

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In the generation of the standard GRACE gravity fields, the K-Band Ranging (KBR) system data is used in its range-rate mode. Because time derivatives attenuate the gravity signal relative to the data noise at the lower frequencies, it is thought that solutions using range data might have better low-degree (low-frequency) characteristics. The purpose of this work is to detail the methods required to generate range-based solutions, to determine some of the properties of these solutions, and then to compare them to range-rate-based solutions. It is demonstrated that range-based solutions are feasible, and that the most effective KBR parameterization in this analysis is to estimate the bias parameter four times per orbital revolution, the bias-rate parameter twice per revolution, and the bias-acceleration and periodic parameters once per revolution. This parameterization yields an improvement in the accuracy of the earth oblateness term, C20, of almost a factor of three, compared to an independent measurement. However, this improvement comes at the expense of the accuracy of the higher-degree gravity coefficients.


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