Safe spacecraft swarm deployment and acquisition in perturbed near-circular orbits subject to operational constraints

Abstract

This paper presents a set of deployment and formation acquisition procedures for spacecraft swarms in perturbed near-circular orbits subject to operational constraints. Specifically, two open-loop command sequences are developed that allow a mothership to deploy a large number of deputies into passively safe formations. These formations guarantee a user-specified minimum separation between all spacecraft in either the orbit plane or the plane perpendicular to the flight direction. Following the open-loop deployment sequence, all deputies are required to passively drift for a specified time in order to accommodate commissioning operations such as de-spin and sensor and actuator calibration. At the end of the commissioning phase, a nonlinear low-thrust control law is engaged to acquire the desired formation and counteract any errors introduced in the deployment sequence. Additionally, analytical lower bounds on the duration of the passively safe relative motion after deployment are derived as functions of deployment uncertainty parameters. These bounds can be used to define requirements for the deployment system and specify the duration of the commissioning phase to ensure passive collision avoidance until actuation capabilities are established. The proposed deployment and formation acquisition procedures are validated through simulations using a high-fidelity numerical orbit propagator. The results of these simulations demonstrate that the proposed procedures provide a means of safely initializing swarm formations at low delta-v cost in low earth orbit.