2015.B.1.4. Lunar orbit stability for small satellite mission design

Author(s)

Andres Dono (1,2)

NASA Ames, United States of America
Universities Space Research Association, United States of America

Session

B.1

Keywords

Orbital Mechanics, Lunar CubeSats, Science, Mission Design, gravity fields, trajectory design

Abstract

The irregular nature of the lunar gravity field severely affects the orbital lifetime and behavior of any lunar satellite mission. In particular, lunar CubeSats have very limited propellant mass to support extensive orbital maintenance and end-of-life requirements. Such spacecraft need stable orbits that do not require large ΔV budgets for station-keeping maneuvers.

The initial Keplerian elements of any lunar orbit are critical to address its stability and to anticipate its evolution. This publication identifies and classifies stable regions that depend on the initial conditions at the time of lunar orbit insertion. High fidelity numerical simulations, utilizing the LP150Q and GRAIL gravity models, were performed to support this analysis.

The focus was placed on low altitude orbits where orbital propagation is strongly influenced by unevenly distributed lunar mass concentrations. For altitudes within 50-200 km, it was found that specific inclinations provide long term stability for any initial circular orbit. Some missions need to maintain a quasi-stable evolution of their orbital elements in order to satisfy certain constraints. Therefore, an analysis of optimal frozen orbits was completed to find methods that save propellant mass by minimizing the number of required maneuvers.

For orbits in the non-stable regions, an assessment of the lifetime was performed. Station keeping and transfer maneuver strategies are presented herein in order to enable any type of low cost lunar small satellite mission.