Low Earth Orbit Positioning, Navigation and Timing (LEO-PNT)

OBJECTIVE: Develop and demonstrate a hardware/software approach for Positioning, Navigation and Timing (PNT) using Low Earth Orbiting (LEO) satellites as a component in the context of the PNT Operating System (pntOS). DESCRIPTION: The near term expansion of internet service to include commercial broadband low earth orbiting (LEO) satellites provides a potential for robust PNT, using their waveforms as Signals of Opportunity (SOOP). Unlike Global Navigation Satellite Systems (GNSS), such as GPS, which has an infrastructure to maintain very precise time throughout the constellation, and satellites with specially designed transmitters, clocks, and a waveform dedicated to the PNT function, SOOPs by their nature are in space for another purpose and not optimized for PNT. Therefore, the challenge for this topic is to exploit features of the SOOP waveforms designing innovative techniques in order to establish range to satellites and henceforth provide the user with the dismount/platform's position and current time (desired). The technology developed under this topic will result in an approach for LEO-PNT that is intended for dismounted Soldiers and Mounted vehicular applications, but may have further applications to aerial, munition and missile applications. The design will use a software defined receiver approach and be capable of incorporation as a component in the context of the Army's pntOS program enabling maximum application. This technology although designed to work standalone can be used to complement existing navigation sensors that are typically used in navigation systems, including GPS. Expansion to the usage of multiple constellations will serve to optimize performance and resiliency in an RF challenged environment. LEO satellites closer proximity to Earth and signal structures can allow for higher signal powers to reach the end user. Investigations conducted under this topic will include technical design approaches that will improve PNT performance (position and timing (desired) accuracy) and also the ability to operate in RF challenged environments such as dense urban, mountainous, forested and jungle environments. It's recognized that many implementations of SOOPs use reference stations in surveyed/fixed based locations. For most Army applications reference stations are undesirable due to the logistics burdening associated with manning the station, redeploying it as the unit maneuvers from location to location, emplacement/survey of the station to support operations and the required command and control for the system. A goal of this program is to develop a LEO PNT SOOP technical approach that will not require a reference station. However, cooperative PNT methods that share information using networks sharing information between unit platforms/members is encouraged. However, caution is required not to over burden the network. Metrics that will be assessed include position and time (desired) accuracy, availability of service (analyzed across the earth), bandwidth usage of a network, Size, Weight and Power (SWAP), complexity associated with system initialization and overall set up time. PHASE I: Develop a design for the LEO-PNT system architecture. Determine requirements and conduct a hardware and software functional allocation for the system. The intended system at a minimum will be relevant to operations for dismounted Soldiers and Mounted. Develop system error budgets supporting the performance metrics, providing allocations to the various elements of the system design, transmission medium, local environment, and selected SOOPs, for supporting operations for the intended applications. Conduct necessary trade studies and modeling and simulation that will contribute to the architecture definition, determine feasibility and reduce risk in Phase II. The primary product of Phase I will be a system specification for LEO PNT and how it can be integrated with existing navigation systems. PHASE II: Design and build a system prototype that is capable of supporting demonstrations by dismounted Soldiers and in Mounted as a plug n play capability for incorporation within the Army pntOS. The initial prototype may be scaled in terms of capacity (numbers of compatible LEO SOOP constellations, minimum for Phase II will be 2), but it should be proven that full scale operation is feasible with the resulting design. Use cases to be demonstrated are dismounted Soldier and Mounted, proving sufficient PNT capability in open range, forested/jungle, and urban. Metrics mention in the Description will be evaluated. PHASE III DUAL USE APPLICATIONS: This topic has the potential to scale and continue to grow and support the entire Army (perhaps DOD) PNT ecosystem. Continued development and refinement of the system will be further expanded in terms of compatibility with additional SOOP constellations, and improvements made through cooperative sharing of information. This capability could easily be accommodated to a commercial capability supporting non-military functions, for virtually an unlimited number of applications. REFERENCES: 1. Fused Low-Earth-Orbit GNSS, Peter A. Iannucci and Todd E. Humphreys, Radionavigation Laboratory The University of Texas at Austin; 2. Performance Evaluation of Navigation Using LEO Satellite Signals with Periodically Transmitted Satellite Positions; Christian T. Ardito, Joshua J. Morales, Joe J. Khalife, Ali A. Abdallah, and Zaher M. Kassas, University of California, Irvine; 3. Navigation using Carrier Doppler Shift from a LEO Constellation: TRANSIT on Steroids; Mark L. Psiaki, Virginia Polytechnic Institute and State University; 4. Leveraging Commercial Broadband LEO Constellations for Navigation: Tyler G. R. Reid, Andrew M. Neish, Todd F Walter, & Per K. Enge KEYWORDS: Positioning, Navigation and Timing (PNT), Assured Positioning, Navigation and Timing (APNT), Low Earth Orbiting (LEO), Army PNT Operating System (pntOS), Signals of Opportunity (SOOP)