Toward Optimal Placement of Free-Space Optical Terminal on the Spacecraft Body

Abstract

Free-space optical (FSO) links have emerged as a promising so-lution for enabling high-speed data transfer in networked space sys-tems. These links leverage highly directed optical beams amplifiedby telescopes that can be oriented using gimbal engines. However,the gimbal’s limited swipe range poses a challenge in optimizing theplacement of the FSO terminal on the satellite body. This placementdirectly impacts the feasible contact time, which is constrained by thegimbal motors’ degree of freedom and speed as the satellites followtheir orbital trajectories. In this article, we address the problem ofoptimizing the FSO terminal placement to maximize the aggregateeffective contact time with the target. First, we formally describethe problem assumptions and perform baseline case studies to gainvaluable insights. Next, we define appropriate metrics that capturethe contact time performance to evaluate different placement strate-gies. Our core contributions are two heuristics, simulated annealing,and an evolutionary genetic algorithm to optimize the FSO terminalplacement. We finally demonstrate through extensive simulation andanalysis that our proposed optimization approaches can significantlyimprove the baseline contact time by up to 27.7%. These findings high-light the potential of employing sophisticated optimization techniquesto enhance the performance of FSO links.