Low-Thrust Control of a Lunar Mapping Orbit
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.
N. Harl and H. Pernicka, "Low-Thrust Control of a Lunar Mapping Orbit," Journal of Guidance, Control, and Dynamics, American Institute of Aeronautics and Astronautics (AIAA), May 2009.
The definitive version is available at http://dx.doi.org/10.2514/1.37098
Mechanical and Aerospace Engineering
United States. National Aeronautics and Space Administration
Keywords and Phrases
Continuous-Low-Thrust Propulsion; Low-Altitude; Lunar Mapping Orbit; Near-Polar; Sun-Synchronous
Article - Journal
© 2009 American Institute of Aeronautics and Astronautics (AIAA), All rights reserved.