Title

Low-Thrust Control of a Lunar Mapping Orbit

Abstract

A method is presented for establishing and maintaining a lunar mapping orbit using continuous-low-thrust propulsion. Optimal control theory is used to maintain a lunar orbit that is low-altitude, near-polar, and sun-synchronous, which are three typical requirements for a successful lunar mapping mission. The analysis of the optimal control problem leads to the commonly seen two-point boundary-value problem, which is solved using a simple indirect shooting algorithm. Simulations are presented for a one-year mapping duration, in which it is shown that an average control force of 0.5 N for a 1000-kg-class spacecraft is required to rotate the orbit plane at the sun-synchronous rate. Because this amounts to a total _V of roughly 15 km=s, a fairly large propellant mass of 416 kg would be required from a typical ion thruster for a one-year mission. However, if the science requirements can be fulfilled in a shorter 1-2-month mission, the required propellant mass could be drastically reduced. Also, it is shown that if the desired control accuracy of the sun-synchronous ascending node is relaxed, the required thrust levels can be decreased by roughly 0.2 N.

Department(s)

Mechanical and Aerospace Engineering

Sponsor(s)

United States. National Aeronautics and Space Administration

Keywords and Phrases

Continuous-Low-Thrust Propulsion; Low-Altitude; Lunar Mapping Orbit; Near-Polar; Sun-Synchronous

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2009 American Institute of Aeronautics and Astronautics (AIAA), All rights reserved.

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