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Optimal orbit-raising and attitude control of all-electric satellites
Sreesawet, Suwat
Sreesawet, Suwat
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Dissertation
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2018-12
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Abstract
Electric propulsion is gaining popularity among satellite operators due to its fuel
e ciency. However, electric propulsion has the limitation of producing a small magnitude of
thrust, meaning that the transfer time to geostationary orbit is of the order of several months.
The long transfer time adds more complexity to the mission design process due to the long
exposure to hazardous radiation belts. Obviously, thrusters require electric power that is
generated from sunlight by satellite solar panels. Therefore, the earth's shadow signi cantly
impacts the orbit-raising maneuver.
This study proposes a novel, robust, and fast numerical methodology for generating
low-thrust trajectories to the geosynchronous orbit. This methodology utilizes a new set of
state variables that has a physical interpretation and exhibits slow variation under a small
magnitude of thrust. The absence of mathematical singularities in the equatorial plane
adds to the bene ts. The new set of state variables, along with a closed-loop guidance
scheme and direct optimization methodology, is used to optimize the satellite trajectory.
An unconstrained optimization scheme is able to robustly and rapidly generate low-thrust
orbit-raising trajectories for a variety of mission scenarios, various initial orbits, application
of electric battery to allow thrusting during eclipses, and orbital perturbations due to the
earth's oblateness or a third body. The proposed methodology can be seamlessly integrated
into receding horizon control scheme, which recomputes the minimum time trajectory at
regular intervals referred to as planning horizon.
The attitude of spacecraft must also be maintained in a desired direction which can be
time-varying. Regular satellites perform orbit-raising using stowed solar array. In contrast,
all-electric satellites perform orbit-raising using deployed solar arrays. Therefore, simple
inverse controllers for attitude control with a neural network-based observer has been studied
and evaluated. We demonstrate that the performance of the inverse controller is drastically
improved with the proposed observer.
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Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Aerospace Engineering
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Wichita State University
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Copyright 2018 by Suwat Sreesawet
All Rights Reserved