Evaluation of the EGM2008 Gravity Model

Satellite orbit fit is one traditional measure of the gravity model accuracy in primarily the long-wavelength. This is a particularly demanding test for the GRACE-based gravity models because Earth gravity models had previously depended on the tracking to various geodetic satellites to determine the low degree part of the field, which led to these fields being noticeably tuned to their particular orbit inclinations. Satellite Laser ranging (SLR) data from a global network of well-determined tracking stations can provide an unambiguous and precise measurement of the satellite orbit accuracy, especially for compact spherical (cannonball) satellites such as Starlette, Stella, Ajisai, LAGEOS-1 and -2. These satellites, along with the BE-C satellite, are an important resource for measuring the long-term variations of the Earth’s gravity field [Cheng and Tapley, 2004]. Table 1. Orbit characterization of satellites used in test