A Framework for Heterogeneous Satellite Constellation Design for Rapid Response Earth Observations

Earth Observation (EO)satellite constellation design deserves further investigation for optimizing configurations that enhance space mission performances. In recent years, there has been considerable interest in reducing the System Response Time (SRT)of EO satellites - the interval between request submission and availability of the image product - in order to achieve rapid response in case of natural or man-made disasters or matters involving defense and natural security. This key performance indicates to the user when, after the request submission, the image produced will be available to him. The best way to improve this performance metric is using heterogeneous constellations, where two different functional constellations are cross-linked; one is mainly for imaging and the other is a communication constellation that is dedicated to relaying commands delivery from Earth station to imaging satellites and data collection back to Earth. This scheme has been proposed before in the previous work to explore its potential enhancement of system performance, or to evaluate the network performances by comparing candidate relay constellations for servicing remote sensing satellites. However, methods for satellite constellation design of this scheme have not been introduced. Since the best heterogeneous configuration may require studying several constellation combinations, this paper presents a framework capable of generating thousands of heterogeneous constellation configurations based on predefined Design Variable (DV)ranges and sizing those configurations in terms of the predefined Measure of Performances (MOPs). Using Systems Tool Kit (STK)and its various add-on modules, we introduce multiple solutions to configure both the imaging and relay constellations of the heterogeneous constellation systems that can achieve their objectives and improve the overall system performance by reducing the SRT. One of these solutions is an imaging constellation of 8 satellites equally distributed in 2 different planes, a Sun-Synchronous Orbit (SSO)and a Mid-Inclination Orbit (MIO). We select this constellation based on the global daily coverage percentage and the satellite optical sensor parameters. In order to reduce the maximum SRT, we select a relay constellation in a Medium Earth Orbit (MEO)on an Equatorial plane and a location of a Ground Station (GS)as a receiving and transmitting Earth site.