SWIFT: Electronically-Reconfigurable Surfaces for Improved Coexistence Between Radio Astronomy and Satellite Communications Systems

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The next few years will see a dramatic increase in the use of satellites in low Earth orbit to deliver world-wide continuous broadband low-latency communications to rural and remote locations. Radio telescopes will need to contend with increased interference from satellites in the largest sidelobes. The gap between what can be achieved by spectrum regulation and administrative coordination, and what is needed for productive science, must be bridged by technical methods. This project intends to study the use of electronically-reconfigurable surfaces (ERS) to enable large reflector antennas to dynamically modify their sidelobes. ERS is an array of patch-type antennas with characteristics that can be individually electronically controlled. Such an array in the outer portion of a dish antenna can strongly reduce interference from the side. However, the characteristics of the dish must be known. The extent to which this problem can be ameliorated by spectrum regulation or administrative coordination between satellite system operators and radio astronomers is limited: Ultimately, satellite system operators have the right to operate at the carrier frequencies allocated to them, whereas astrophysical considerations dictate the need to observe at times and frequencies affected by these transmissions. The gap between what can be achieved by spectrum regulation and administrative coordination, and what is needed for productive science, must be bridged by technical methods. A practical ERS occupying the outer 17% of a reflector can effectively null interference from any from direction beyond the main lobe, with negligible effect on gain and pattern within the main lobe. The principal difficulty in the implementation of a practical ERS is control; that is, determining the set of unit cell phase shifts that implements the desired pattern. Because the sidelobes of large reflectors are not accurately known, and because interference direction of arrival is rapidly varying, any deterministically determined solution will be approximate at best, so real-time optimization will be required. This research will investigate the use of ERS for practical coexistence between radio astronomy systems and satellite transmissions, potentially leading to advanced, wide-ranging sharing techniques applicable to many situations. It will also support undergraduate students in a project that addresses a full range of issues.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.