DESIGN CONSIDERATIONS IN RAPID-REVISIT SMALL SATELLITE CONSTELLATIONS

摘要

Earth observation satellites provide an invaluable supply of imagery for a range of applications. However most current systems consist of a single satellite, or a small constellation, which imposes a number of limitations including restricted coverage and limited revisit. The common use of sun-synchronous orbits for optical imaging satellites also means that passes are highly predictable and limited to a narrow time band each day. A moderately sized constellation of small, low cost optical satellites, providing high resolution imagery and operating in a low inclination orbit in multiple planes, can provide frequent imaging to key areas of interest throughout the day allowing information updates with timeliness of the order of minutes. Coupled with a supporting ground and communications architecture which maximises the responsiveness of the system (minimising the total latency from image tasking to product delivery) enables applications including tracking and monitoring, change detection, pattern of life assessments and support to humanitarian or disaster operations. However, even a modest constellation (i.e. less than 50 satellites) requires the satellite design to be optimised such that manufacturing and testing processes can be highly automated allowing each satellite to be produced quickly. This opens up the possibility of more ambitiously sized systems akin to the mega constellations currently under development for communication applications. This paper presents the benefits and issues associated with deploying and operating a constellation of imaging satellites and describes several viable design concepts, including a Rapid Revisit Constellation, consisting of high resolution optical imaging satellites providing a GSD of~1 m, designed to be quickly manufactured at a low cost, and able to provide extremely high revisit rates over key target areas. The paper also discusses potential exciting applications and utility of constellations of the future.