Simulation of a Future SLR Satellite to Improve Low‐Degree Gravity Estimates

Abstract

AbstractThe Gravity Recovery and Climate Experiment (GRACE; 2002–2017) and GRACE Follow‐On (2018‐present) have observed Earth's monthly mass change with unprecedented spatial resolution. These missions have long relied on satellite laser ranging (SLR) measurements to replace the C2,0 coefficient, which GRACE recovers poorly. Recent work has also shown the need for SLR‐determined C3,0 when GRACE operates with a single accelerometer. However, it was not until the 2012 launch of the Laser Relativity Satellite that the SLR data gained the sensitivity to recover C3,0 accurately. These low‐degree gravity coefficients represent large‐scale mass transport and small changes in their values have implications for ice sheet, ocean mass, and water storage estimates. To fully exploit SLR's utility for time‐variable gravity (TVG), future satellite orbits should be selected to maximize their sensitivity to the gravity field. In this work, we present results from a simulation study of a hypothetical SLR satellite in which we generate 1 year of data to satellites placed across varying inclinations. We also simulate seven current SLR satellites to show realistic improvements from the new satellite. When compared to the known truth input, a low‐inclination satellite (<∼ 45°) most improves the low‐degree gravity terms, especially the even zonals which show a significant decorrelation. From this, we investigate recovery of the annual variability in the simulated signal and find recovery of the sine component improves by up to 41%. This has important implications when considering future SLR satellites in the context of TVG.