Cislunar Navigation Technology Demonstrations on the CAPSTONE Mission

The Cislunar Autonomous Positioning System Technology Operations and Navigation Experiment (CAPSTONE) mission is an upcoming lunar flight demonstration, with a targeted launch in early 2022. The primary objective of the mission is to test out navigation and operations in the same Near Rectilinear Halo Orbit (NRHO) that will be utilized by NASA’s Lunar Gateway. In addition to this objective, CAPSTONE contains a dedicated flight board for the Cislunar Autonomous Positioning System (CAPS), a framework for autonomous or near-autonomous navigation in cislunar space developed by Advanced Space. During the mission, CAPS will demonstrate onboard orbit determination via both one-way uplink measurements and crosslink radiometric measurements with the Lunar Reconnaissance Orbiter (LRO). This paper previews the expected performance of these two experimental data types with a set of high-fidelity simulations using realistic CAPSTONE concept of operations (CONOPS) and radio specifications. For CAPSTONE, the nominal tracking architecture will rely on the standard two-way radiometric measurements of the Deep Space Network (DSN) – CAPS is intended is a technology demonstration. However, solutions will be processed onboard, and the expected navigation performance of these experimental data types are compared against the expected ground-based navigation performance. The goal of CAPS is ultimately to provide a framework for autonomous navigation in cislunar space. The CAPS experiments onboard CAPSTONE will be the first on-orbit step towards this goal. While the early experiments will not replace the utilization of ground-based navigation, they should be able to supplement it and work towards a future where the reliance on two-way ground networks is greatly reduced. For the CAPSTONE orbit and radio specifications, the one-way uplink measurements are expected to provide navigation solutions with uncertainties on the order of single kilometers in position and single cm/s in velocity. These solutions could, in theory, be utilized to design stationkeeping maneuvers onboard the spacecraft and maintain its NRHO over time. Simulations of the expected crosslink measurements also show navigation performances similar to the expected performance of two-way tracking. In addition to examining the CAPSTONE operational CONOPS, the performance of a conceptual ground-based one-way beaconing system is examined, compared to standard two-way radiometric tracking, and used in conjunction with the expected crosslink performance to study what may be possible in terms of cislunar autonomous navigation provided by CAPS in the future.