Concept of Operations for SWARM-EX: a Three CubeSat Formation-Flying Mission

The Space Weather Atmospheric Reconfigurable Multiscale Experiment (SWARM-EX) is a distributed aeronomy instrument consisting of three 3U CubeSats operating in low Earth orbit. Supported by the National Science Foundation and NASA’s CubeSat Launch Initiative, SWARM-EX aims to accomplish a challenging set of scientific and engineering objectives. The mission’s scientific goals are focused on addressing outstanding aeronomy questions by making in-situ measurements of the equatorial thermosphere anomaly and equatorial ionization anomaly using Flux-Probe-Experiment and Planar Langmuir Probe sensors onboard each spacecraft. Engineering objectives are focused on advancing the state of the art in CubeSat swarming through a series of demonstrations and experiments. This paper presents three innovations that will enable SWARM-EX to overcome its significant challenges. First, the scientific objectives are formalized as a set of Primary Science Questions and Secondary Measurement Demonstrations, which are then translated into the spatial and temporal scales over which in-situ measurements must be made. These scales are then used to define the relative orbit geometries which the spacecraft must achieve. Second, a guidance, navigation, and control system is introduced which is able to acquire and maintain the required relative orbit configurations. The proposed system requires minimal input from controllers on the ground, provides passive safety at small inter-spacecraft separations, and is able to efficiently achieve large swarm reconfigurations with minimal propellant consumption by utilizing a novel hybrid propulsive/differential-drag control methodology. Third, a concept of operations is presented which enables the time-and propellant-efficient achievement of the mission’s objectives while providing significant tolerance to on-orbit anomalies. The concept of operations is discussed in detail, including (1) the specific mission objectives to be addressed at each phase, (2) the control methodologies to be used at each phase and during transitions between phases, as well as the trade-offs associated with the different methodologies, and (3) ∆v budgets by phase and explanations for how they were obtained.