  This work utilizes a particle swarm optimizer (PSO) for initial orbit
determination for a chief and deputy scenario in the circular restricted
three-body problem (CR3BP). The PSO is used to minimize the difference between
actual and estimated observations and knowledge of the chief's position with
known CR3BP dynamics to determine the deputy's initial state. Convergence is
achieved through limiting particle starting positions to feasible positions
based on the known chief position, and sensor constraints. Parallel and GPU
processing methods are used to improve computation time and provide an accurate
initial state estimate for a variety of cislunar orbit geometries.
