Formation Design of Distributed Telescopes in Earth Orbit for Astrophysics Applications

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This paper presents a new formation design that enables deployment of large distributed telescopes aligned with inertial targets in Earth orbit. To minimize propellant consumption, the proposed design uses a two-phase operations concept including observations and formation reconfigurations. During observations, a quasi-continuous control system negates the relative acceleration perpendicular to the line of sight, allowing the interspacecraft separation to passively drift. After each observation, a formation reconfiguration is performed to ensure proper alignment with the target at the start of the next observation. Absolute and relative orbits that minimize the total delta-v cost of a specified mission profile are derived in closed-form including effects of perturbations such as Earth oblateness. Additionally, a new stochastic model predictive control architecture is proposed that uses an optimal impulsive control algorithm to efficiently control the formation. The performance and value of the proposed formation design are demonstrated through high-fidelity simulations of a reference mission to image the exoplanet AEgir using a small starshade and telescope. The results of these simulations demonstrate both that the proposed formation design globally minimizes the delta-v cost of the mission and that the mission is feasible with current propulsion technologies.