Protecting Satellite Communications

Using a CubeSat array to identify interfering Earth transmitters

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Many missions fulfilled by the service branches depend upon satellite communication links. Imagine a situation where those links were blocked by a terrestrial jammer. You don’t know where the jammer is coming from and what bands of the RF spectrum are being blocked.

THE CHALLENGE

Communications between U.S. government satellites and the ground are disrupted on occasion by interfering terrestrial transmissions. If the location and frequency of this interference can be identified it is possible to work with the offending party to discontinue transmission.

WHY IT MATTERS

This project set out to determine whether a set of CubeSats with field programmable gate array (FPGA) processors flying in formation can be used to detect and geolocate a terrestrial interferer. Satellite operators use terrestrial links at X/Ku/K/Ka/Q bands for satellite space-to-ground communications. These links are used to monitor satellite health, perform station-keeping, and transmit payload data to the ground. In these same radio frequency (RF) bands, there are many terrestrial transmitters that might interfere with satellite communications. This interference can range from short-term disruption to long-term disabling of a satellite. There are no satellites that can fill the global mission of detecting, characterizing, and geolocating transmissions that interfere with satellite communications. Historically, the cost to put a formation of satellites on orbit has been prohibitive because of the required power and complex signal processing.

THE SOLUTION

Rincon Research Corporation (RRC) has 35 years of experience in geolocation. The company also has 15 years of experience in developing FPGA RF signal processing tools for terrestrial and space operation. For this project we designed Low Earth Orbits (LEO) and developed budgets including power, heat, and RF communications links to determine the requirements for a CubeSat formation to fulfill the geolocation mission. We then identified an FPGA processor with size, weight, and power sufficiently low to be a CubeSat payload. RRC already has a product called the Low Power Front End (LPFE) that includes this FPGA and an RF receiver and is used for testing.

"”We developed a payload capable of detecting and geolocating terrestrial jammers from a formation of low earth orbiting satellites that are small enough to hold in your hands!”" — Dr. Sid Henderson

HOW IT WORKS

Our first task was to design an engineering model system for in-the-loop testing of the FGPA payload. We created a cubesat bus engineering model with components necessary to test the function of the payload. The model included a simulated flight command and control board, GPS receiver, power supply, and ground station commands. A space environment simulator was also developed that generates RF signals and modifies them so they appear to have been transmitted from a specified location on the Earth and received by the orbiting payload. Our second task was to develop FPGA code for detection and geolocation of RF signals. This included development of algorithms, analysis of methods to improve time and frequency synchronization, analysis of geolocation parameter estimation, and an assessment of resiliency to failure of one or more cubesats in the formation. Previously developed RRC code for RF signal collection was leveraged as well. This code was installed on the LPFE which served as our payload engineering model. We inserted the LPFE into the bus and space-environment engineering models and conducted in-the-loop testing of the FPGA software. A variety of orbits and signals were used to successfully demonstrate code performance.

IMPACT FOR THE FUTURE

Service members rely upon robust communications to fulfill their mission. Outages can delay fulfillment of their duties, or even impede completion of their mission. This project enables identification and mitigation of signals that interfere with these communications.

This activity has had significant impact on RRC. Based on lessons learned from this project RRC has developed an FPGA signal processor called the Astro Software Defined Radio (ASDR) that meets all of the size, weight, and power requirements for the geolocation mission with cubesats. The processor is capable of performing a large range of signal processing mission in space.

To date RRC has sold eight ASDRs to government or industry customers. Further, RRC has won contracts to develop FPGA signal processing software that will be loaded on an ASDR and launched into orbit. Two of these are to be launched in early 2018 as a demonstration mission for the Department of Homeland Security. RRC has written multiple proposals to use the ASDR for space based signal processing.

“The Air Force can deploy these cubesat into orbit at a very low cost, providing protection to our vital space communication links.” — Dr. David Haycock, Mission Liaison / Systems Engineer at Rincon Research Corporation

DHS Tests Emergency Beacon Geolocation in Arctic

The Department of Homeland Security is leveraging FPGA software from this project and the RRC ASDR payload to fulfill a Coast-Guard emergency beacon detection mission in the Arctic. The first test flight is scheduled for February, 2018.

Rincon Research Corporation

www.rincon.com

Tucson, Arizona

RRC has supported our countries intelligence missions for 35 years. We specialize in Radio Frequency signal processing. RRC founder Michael Parker is a recipient of the prestigious NRO Pioneer Award and identified as the “First to perform TDOA/FDOA geolocation from space.”

Sid Henderson, Ph.D. Sid Henderson, Ph.D.

Sid Henderson, Ph.D.

Program Manager / Principal Investigator

David Haycock, Ph.D. David Haycock, Ph.D.

David Haycock, Ph.D.

Mission Liaison / Systems Engineer

Ervin Frazier Ervin Frazier

Ervin Frazier

Senior Scientist

TOPIC TITLE:

Space-based RF emitter detection and localization using field programmable gate arrays

TOPIC NUMBER:

AF141-124

CONTRACT NUMBER:

FA9453-15-C-0458 in fulfillment of CDRL A003

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