A novel method to evaluate the trajectory dynamics of low-thrust spacecraft is developed. The thrust vector components are represented as Fourier series in eccentric anomaly, and Gauss's variational equations are averaged over one orbit to define a set of secular equations. These secular equations are a function of only 14 of the thrust Fourier coefficients, regardless of the order of the original Fourier series, and are sufficient to accurately determine a low-thrust spiral trajectory with significantly reduced computational requirements as compared with integration of the full Newtonian problem. This method has applications to low-thrust spacecraft targeting and optimal control problems.

to initiate your request. See also AIAA Rights and Permissions www.aiaa.org/randp. *Associate Professor, Department of Mechanical and Aerospace Engineering. Member AIAA.

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Table 3 Summary of best micropropulsion systems to achieve various types of CubeSat maneuvers Maneuver type Key thruster properties Thruster types Small maneuvers (e.g., station keeping, launch error correction) Low power, small thruster, and propellant mass/volume Cold gas, electrospray, pulsed plasma Maximum orbit change given time constraints High thrust, high propellant density Green monopropellant Large orbit changes (e.g., LEO to GEO or Earth escape) High I sp , range of power and thrust Electrospray, helicon plasma, ion thruster ‡ ‡ Private communication with Colleen Marrese-Reading to

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