Analysis challenges for spaceborne multi-technique mass-change measurement: Mechanisms and mitigation

Considerable research is underway in the satellite geodesy, spaceflight engineering, and high-precision metrology community that brings to bear modern technology to next generation mass-change estimation. This is motivated by a consensus community desire for ever increasing resolution and accuracy of global mass change - an essential climate variable - for understanding and inference of the Earth system at all spatio-temporal scales. The infusion of high-precision modern technology brings with it additional challenges in the data analysis including fundamental enabling analyses such as attitude and orbit determination, modeling of the observation and its connection to the gravity field parameters, and estimation techniques to maximize the fidelity of spatial patterns and signal amplitudes in estimated mass-change fields. In this paper, we report on our investigations into the mechanisms of aliasing - one of the most visible challenges in mass-change estimation from satellite gravity observations. In prior work, we have presented symptomatic assessments of how aliasing can have orthogonal impacts on gravity field estimated from low-low satellite-to-satellite (SST) tracking and from gravity gradiometry (GG), and shown how a combination of the two in a hybrid configuration can offer the best of both techniques. In this follow-up paper, we present results of closer investigations into the mechanisms of aliasing and their differential impacts on SST and GG, and what this suggests for mitigation in future multi-technique mass-change measurement environment. These results form the basis for recommendations of analysis techniques such as appropriate modifications to the variational methods, scoping the requirements on prior knowledge of rapid mass variability that is the principal cause of aliasing errors, and their mitigation in estimation techniques.