A high-speed, low-cost solution for optical communications ground photon counting receivers
Real Time Optical Receiver (RealTOR) Project
The Real Time Optical Receiver (RealTOR) Project at NASA Glenn Research Center is focused on using commercial-off-the-shell (COTS) technologies to develop a portable, scalable, modular, low-cost solution for optical communications ground receivers. NASA is continuously working to advance optical communications technologies to meet the demand for higher communications data rates, by developing and testing low-cost ground-based optical receivers for space-to-ground communications. Optical communications encode data into a beam of light which is then downlinked directly from a satellite or via a space relay to Earth based ground system optical terminals. Advanced optical communications system will be required for future space explorations systems. In addition to developing a low-cost solution for optical communications photon counting ground receivers, the RealTOR Project has developed a field programmable gate array (FPGA)-based transmitter to test the RealTOR System, and is currently conducting subsystem integration, testing and demonstration efforts.
The RealTOR system implements the Consultative Committee for Space Data Systems (CCSDS) Optical Communications High Photon Efficiency (HPE) standard, which will be used in future photon counting missions such as the Optical Artemis-2 Orion Communications (O2O) mission.
The RealTOR project has several subsystems under development, including the transmitter FPGA, atmospheric link emulation, and the RealTOR system, which consists of the fiber device, COTS Superconducting Nanowire Single-Photon Detectors (SNSPDs), and FPGA-based receiver.
The RealTOR system is designed to receive a serially concatenated pulse position modulation (SCPPM) waveform, compliant to CCSDS HPE standard, and uses multiple individually fiber coupled to SNSPDs in parallel to scale to a required data rate. RealTOR system aims to achieve data rates up to 530 Mbps in real time in support of O2O Low-Cost Optical Terminal (LCOT) demonstration at Goddard Geophysical and Astronomical Observatory (GGAO), and future optical communications low-cost ground station efforts.
Future Technology Applications
The RealTOR low-cost receiver aims to increase the use of photon counting optical communications and infuse internationally the use of the CCSDS Optical Communications HPE standard. This development is anticipated to increase reliability and affordability of ground-based photon-counting optical receivers for both government and industry applications.