Orbit design for satellite swarm-based interferometric radiometers for super-resolution earth observation

Abstract

Soil moisture and ocean salinity mapping by earth observation satellites has contributed significantly towards a better understanding of the earth’s climate and hydrosphere. Nevertheless, an increased spatial resolution of radiometric data could yield a more complete picture of global hydrological and climate processes. High-resolution radiometers, such as SMOS, have already approached prohibitive sizes for spacecraft due to the required large antenna apertures. Radiometer concepts based on satellites flying in close proximity have been proposed as a possible solution. Individual receivers placed on a large number of smaller satellites orbiting a central satellite would form a combined interferometric array. Recent technological progress in formation flying, satellite miniaturisation, inter-satellite links and data processing could make a future satellite swarm-based radiometer possible. The design of such a system requires a methodology which enables the determination of orbit parameters in a way that optimizes radiometer performance and ensures system feasibility. In the past, the optimization of interferometric array configurations has only aimed to optimize the image quality without taking into account system constraints, such as satellite collision risk, satellite fuel consumption and other feasibility considerations. This resulted in idealized array configurations that might put unrealistic constraints on the satellite system. A current research project of the DLR Microwaves and Radar Institute investigates methodologies for the orbit optimization of large satellite swarm-based interferometric radiometers regarding future earth observation radiometry missions. For this purpose a system simulator has been created for the study of radiometers based on a large number of spacecraft. First results have indicated that an approach based on statistical methods for the quantification of radiometer performance and the use of numeric optimization solvers can yield promising orbit configurations. This paper provides an overview of the optimization approach and first results in generating a feasible and performant satellite swarm configuration for interferometric radiometry purposes.