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Satellite laser ranging (SLR) observations are routinely applied toward the estimation of dynamic oblateness, C20, which is the largest globally integrated component of Earth's time‐variable gravity field. Since 2002, GRACE and GRACE Follow‐On have revolutionized the recovery of higher spatial resolution features of global time‐variable gravity, with SLR continuing to provide the most reliable estimates of C20. We quantify the effect of various SLR processing strategies on estimating C20and demonstrate better signal recovery with the inclusion of GRACE‐derived low‐degree gravity information in the forward model. This improved SLR product modifies the Antarctic and Greenland Ice Sheet mass trends by −15.4 and −3.5 Gt/year, respectively, as compared to CSR TN11, and improves global mean sea level budget closure by modifying sea level rise by +0.08 mm/year. We recommend that this new C20product be applied to RL06 GRACE data products for enhanced accuracy and scientific interpretation. New satellite laser ranging C20solution reveals larger Antarctic and Greenland ice mass losses and mass‐driven sea level riseThe new C20result improves closure of the global mean sea level budget and agreement with an independent Antarctic ice mass assessmentWe recommend this new product for replacing the GRACE C20values for science applications

Orbit determination (OD) approaches operationally model the Tracking and Data Relay Satellites (TDRS) as homogenous spheres for nonconservative force modeling. To improve definitive orbit determination and prediction accuracies, and to employ TDRSS tracking of user satellites within various geophysical investigations, a detailed TDRS spacecraft model has been developed. The enhanced TDRS model represents the spacecraft as a combination of twenty-four flat plates. The radiative forces acting on each plate are computed and vector summed to produce the overall acceleration on the spacecraft center of mass. An initial model, based on pre-launch engineering information, has been refined to better fit observed spacecraft accelerations. The Goddard TDRS-5 Model 3 (GT5M3) improves orbit accuracy, yields better fits to the tracking data, significantly reduces residual accelerations, and improves orbit prediction capability.

On January 11, 1996, the Space Shuttle Endeavor, mission STS-72, was launched, carrying aboard the first of four Shuttle Laser Altimeter (SLA) experiments. In support of SLA-1, precise orbits have been computed from Tracking and Data Relay Satellite System (TDRSS) Doppler observations. In some cases, these data were combined with Global Positioning System (GPS) pseudorange observations. Traditionally, the Tracking and Data Relay Satellite (TDRS) orbits themselves have been the dominant source of error in Shuttle orbit determination during quiescent attitude periods. However, a new technique utilizing TOPEX/Poseidon’s (T/P) precise orbit knowledge plus the TDRSS-T/P Doppler tracking is used to significantly reduce the TDRS orbit errors. That approach, along with improved modeling and parameterization have allowed us to compute precise Shuttle orbits from TDRSS-Shuttle Doppler tracking data. Orbit overlap comparisons indicate these Doppler-derived orbits have a meter level (1σ) radial precision, and they agree radially with the combined Doppler and GPS derived orbits at the 1.5 m level (1σ).