New Methods for Linking Science Objectives to Remote Sensing Observations: A Concept Study Using Single- and Dual-Pair Satellite Gravimetry Architectures
In this manuscript, we present a new analysis tool, called space-time-accuracy grid (STAG) analysis, to simultaneously assess the performance of an observing system architecture across space and time. Such an analysis tool is useful to directly link science objectives (typically expressed via a targeted spatial resolution, temporal resolution, and accuracy) to the expected performance of the observing system architecture. As a proof of concept, we apply STAG analysis to analyze three potential future observing systems for mass change in the Earth system: a single pair of polar orbiting satellites (heritage Gravity Recovery and Climate Experiment and Gravity Recovery and Climate Experiment Follow-On), two polar pairs of satellites, and a polar pair of satellites coupled with an inclined (70°) pair of satellites. Here, we demonstrate the use of STAG analysis to quantify the relative performance of each architecture across space (200-1,800 km) and time (1-30 days), offering a significantly more comprehensive assessment of performance than previous studies. Results show that the polar pair coupled with the inclined pair reduces errors (after state-of-the-art post-processing for each architecture is accounted for) relative to the single pair of satellites by 40-60% in medium spatial scales (500-1,200 km), with the greatest benefit being for longer solution (monthly) timespans. Overall, the results from this case study highlight the importance of increasing the isotropy of the observable over simply increasing the sampling frequency. Some demonstrated benefits of STAG analysis include the ability to incorporate state-of-the-art post-processing methods into the analysis and also tailor the analysis to specific geographic regions to address targeted scientific objectives.