Description: A multi-channel FPGA-based time-to-digital converter (TDC) is needed to process the output from single-photon focal plane arrays used in lasercom. Leveraging an existing 64-channel design shown capable of better than 30 ps. time resolution and 256 channels with 120-ps time resolution, scalable 512-channel (threshold) and 1024-channel (objective) TDCs with optional multicore image processor will be developed, which can process and transmit data continuously. In Phase I, leveraging the existing technology, we will demonstrate existing multichannel TDC processors, including several with single-photon avalanche photodiode (SPAD) detectors. After refining the requirements and generating a controlled specification of NASA requirements, we will then design of the High-channel-count Time-to-digital Advanced Processor (HiTAP) module capable of better than gigaphoton per second rates in a first-in/first-out (FIFO) -buffered continuous stream, with the goal of achieving kilo-channel designs capable of gigaphoton count rates.

Benefits: NASA's Space Communications and Navigation (SCaN) Program Office identified optical communications as an important technology for NASA missions, allowing enhanced volume and quality of data returned from the farthest reaches of space to be achieved in order to prepare for future human deep-space exploration missions. Although several missions have validated optical communications from low-Earth and geostationary orbit, the unique challenges of deep-space optical links still require separate risk-retiring technology demonstrations before implementing inner orbit communication. There a number of NASA applications benefiting from the innovation, including using the single-carrier multiplication avalanche photodiode (SCM-APD) arrays for LADAR autonomous navigation, docking, and landing systems, and in LIDAR instruments for atmospheric sciences. The primary focus of this effort is to develop the SCM-APD for space optical communications.

The innovation will enable low-SWAP space-based, free-space optical communications, terrestrial free-space optical communication, charge particle detectors, photon counting, automotive LADAR, LIDAR, altimetry, time-resolved spectroscopy, fluorescent decay measurements, single-photon detectors, auto- and cross-correlation.