Optimizing Earth Observing Constellations of Satellite Sensors Using ASPEN: A Proof-of-Concept Study for Global NWP and Nowcasting Applications

Abstract The Advanced Systems Performance Evaluation Tool for NOAA (ASPEN) is applied to the problem of optimizing the design of a constellation of sensors by calculating the scientific benefit and cost effectiveness of all possible combinations of sensors within a specified design ensemble (i.e., a catalog of sensors). In this proof-of-concept study, sensors are derived from the NOAA Satellite Observing System Architecture (NSOSA) study, the Geostationary Extended Observations (GeoXO) satellite system program, and the COSMIC-2 mission, and the targeted applications are restricted to two examples, Global NWP and a suite of six nowcasting applications. The results are subject to several caveats, including the use of the current version of the ASPEN inputs and simplified methods of estimating costs. Achieving optimization adopts the approach of visualizing the results as cost–benefit “efficient frontier” scatterplots and identifying the most efficient constellations—the constellations that maximize the benefit for a given cost. The optimal constellation depends strongly on the budget, the sensor costs, the applications considered and their observational requirements and priorities, and the design ensemble of possible constellations. For illustration, a simple decision rule is applied to select the optimal constellation for a given budget. In practice, such guidance must be carefully considered in the context of neighboring constellations, i.e., constellations that are close to the optimal constellation in the efficient frontier scatterplot. In this study, for nominal ($2B annualized) costs, the optimal constellation includes the MW LEO Sounder, GNSS RO System, and VIS IR LEO Imager for Global NWP and the VIS IR GEO Imager, MW LEO Sounder, and IR GEO Sounder for nowcasting. Significance Statement The Advanced Systems Performance Evaluation Tool for NOAA (ASPEN) is designed to be a science-based and efficient tool for comparative assessment of observing systems. ASPEN comparisons of observing system performances to application requirements are “observing system neutral” because the ASPEN interface characterizes the Earth system in terms of geophysical observables and their attributes. The ASPEN benefit combines the degree to which the performances of the observing systems fulfill the application requirements, weighted by the application priorities. Plotting the ASPEN benefit versus the cost of each potential constellation and then identifying those close to satisfying the budget requirements with the greatest benefits should be a useful tool to help optimize the next-generation space-based Earth-observing system.