Orbit Design of a Lunar Meteoroid Impact Flashes Observer

Abstract

Fragments of asteroids and comets constantly encounter the Earth and Moon in their orbits, impacting them as meteoroids. Observations of meteor showers on Earth have been studied for at least 50 years, in order to construct accurate Solar System meteoroid models. More recently, Earth-based telescopic observations of the light flashes produced by lunar meteoroid impacts have revealed useful in the validation and improvement of such meteoroid models. However, Earth-based lunar observations are restricted by weather, geometric and illumination conditions. As such, it has been proposed that a lunar orbiter could improve the detection rate of lunar meteoroid impact flashes. Assessing which orbit a spacecraft should fly in order to detect these flashes and improve current Earth-based observation methods is the aim of this thesis. The study is restricted to spacecraft with the CubeSat format and its inherent limitations, since it is also inserted in the context of the feasibility study of the Lunar Meteoroid Impacts Observer (LUMIO) and ESA’s Lunar CubeSats for Exploration challenge.

A methodology of sequential orbital trade-offs was followed, taking into account acceptance criteria based on the mission requirements and selection criteria based on the research objective. The goal was maximise the number of meteoroid detections, during the mission lifetime, while minimising the mission ∆V budget. Circular Frozen Orbits, Earth–Moon L2 Lyapunov, Halo, Near-Rectilinear, Vertical, Distant-Retrograde and Low-Prograde orbits were selected as candidates, based on a preliminary orbital trade-off. In order to determine the total number of meteoroid detections possible from a certain orbit, the lunar meteoroid environment was modelled and a coverage analysis tool was developed to determine the payload FOV-area in the lunar nightside.

Frozen Orbits were found to allow the detection of meteoroid impacts with kinetic energies too small with respect to the desired, so the design space was restricted to CRTBP orbits. From Lyapunov, Halo, Near-Rectilinear and Vertical Orbits it would be possible to detect between 1000 and 10000 impacts during the mission lifetime, but detections from some DROs could be one order of magnitude larger. Nonetheless, since transfer costs to DROs are known to be high, a Near-Rectilinear Orbit, with a minimal ∆V budget, was chosen as the operational orbit.