OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Space Technology The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop a sensor design that implements a tomographic lidar capable of translating multiple high resolution range measurements from a diversity of look-angles into imagery of remote objects from a moving platform. The lidar sensor system should be capable of <7.5 cm effective range resolution along a single dimension and include computer processor algorithms that can take multiple of these range projections over an angular range of >30 degrees and output a single, high-resolution 2D image of an object. DESCRIPTION: Lidar tomography is a form of reflective tomography that measures laser light reflected off remote objects and reconstructs an image from multiple projected samples of a scene [1]. Lidar systems can provide high-accuracy, range resolved measurements of objects using either time-of-flight measurements or frequency modulated continuous wave (FMCW) measurements. The lidar tomography approaches shares many similarities to those implemented in the commonly used Computed Tomography (CT) scans for medical imaging [2] as well as synthetic aperture radar (SAR) [3]. Some advantages of this approach are that it overcomes several of the traditional limits of optical remote sensing, such as optical diffraction, geometric aberrations, and atmospheric turbulence, through a technique of incoherent aperture synthesis. The goal of this effort is to design and implement a basic prototype of a remote sensing lidar tomography system that uses active illumination from a laser to perform high resolution range measurements of an object. The lidar sensor can be assumed to be on a moving platform such that over time it can take multiple 1D projections of the object over a diversity of angles spanning a range of 30 degrees or more. A 2D range-cross range image can then be reconstructed from this series of 1D measurements using a back-projection type algorithm, for example. With recent improvements in timing resolution from technologies such as superconducting nanowire single photon detectors (SNSPDs) [4], up-conversion single-photon detectors [5], and single-photon avalanche photodiodes (APDs) in the form of Geiger Mode APD (GmAPD) technology [6], there are several prospects for generating high timing resolution of optical pulses better than 500 ps. The use of novel components such as integrated photonics, electro-optical crystals, or other photonic technologies to increase the effective timing resolution of the lidar system is also encouraged. Photon counting approaches may also offer a way to extend the overall sensor range and increase the detection SNR. The tomographic lidar should use a laser transmitter with a wavelength in the near-infrared (NIR) spectrum of roughly 780 nm 2500 nm. The proposed solution should also consider algorithms to form high resolution imagery from the measured tomography data. PHASE I: In this initial phase, tomographic lidar sensor concepts will be developed, evaluated, and computer modeled. Design challenges and trade-offs for an airborne or spaceborne payload will be tabulated and areas in need of additional R&D will be identified. Critical factors to consider are the sensor range resolution, laser power, overall system SWAP, and innovative image reconstruction algorithms that account for platform motion. A feasibility study will be conducted in consultation with relevant stakeholders to develop a significant concept of operations (CONOPS). Preliminary designs should be developed for Phase II which will be assessed based on scientific merit and technical readiness levels. PHASE II: A prototype tomographic lidar will be constructed and tested against key performance metrics. Testing can use a combination of calibrated test targets and 3D objects on rotating platforms to simulate the motion of the sensor. A detailed design for a packaged prototype system will be developed and key components tested. The design and performance will be assess relating to the preparedness of the proposed technology for further development, transition, commercialization, and integration with Space Force operations. Preliminary designs will be made for a Phase III system. PHASE III DUAL USE APPLICATIONS: A breadboard version of the design will be built and tomographic lidar measurements taken in a simulated environment that will test and validate the design to a Technology Readiness Level (TRL-5) for a space payload. The proposed manufacturing process will be evaluated and refined to improve yield while reducing cost. REFERENCES: 1. Van Rynbach, Andre, et al. "Lidar tomography for remote sensing." Laser Radar Technology and Applications XXVIII. Vol. 12537. SPIE, 2023; 2. J. Hsieh, Computed Tomography: Principles, Design, Artifacts, and Recent Advances, SPIE Press, 2003; 3. J. David Munson, J. D. O'Brien and W. K. Jenkins, "A Tomographic Formulation of Spotlight-Mode Synthetic Aperture Radar," Proceedings of the IEEE, vol. 71, no. 8, pp. 917-925, 1983; 4. J. Chang, J. W. N. Los, J. O. Tenorio-Pearl, N. Noordzij, R. Gourgues, A. Guardiani, J. R. Zichi, S. F. Pereira, H. P. Urbach, V. Zwiller, S. N. Dorenbos and I. E. Zadeh, "Detecting telecom single photons with 99.5% system detection efficiency and high time resolution," APL Photonics, vol. 6, p. 036114, 2021; 5. B. Wang, M.-Y. Zheng, J.-J. Han, X. Huang and X.-P. Xie, "Non-Line-of-Sight Imaging with Picosecond Temporal Resolution," Physical Review Letters, vol. 127, no. 5, p. 053602, 2021; 6. http://ridl.cfd.rit.edu/products/publications/lincoln%20lab/13_2geigermode3d.pdf; KEYWORDS: lidar; tomography; avalanche photodiodes; remote sensing; infrared
