Orbital Dust Impact Experiment (ODIE) – A Passive Dust Collector Designed to Address the Dust Flux Data Gap

Monitoring dust particle populations in the vicinity of the Earth is vital to understand and mitigate against the hazards they pose to spacecraft, driving design of effective spacecraft shielding and optimum operational protocols. The flux of particles > few mm orbiting Earth has been investigated remotely using radar and optical telescopes [e.g. 1, 2], revealing that objects in this size range have increased in abundance rapidly since the dawn of the space age. Despite their diminutive size, objects smaller than the radar detection limit are still capable of significant damage to spacecraft. Such particles are expected to be far more numerous, with estimates in the trillions for the total number of particles >100 μm in size [3]. The degree of damage caused by these dust particles is heavily dependent on characteristics such as their relative velocity, impact angle, shape and composition, which vary as a function of origin (e.g. orbital debris originating from human activities in space have relative velocities that are typically slower than for natural micrometeoroids originating from comets and asteroids). It is therefore important to be able to distinguish between these two dust populations, to fully understand the threat posed by these particles. Previous flux measurements for smaller dust populations have largely been based on passive collection surfaces retrieved from dedicated missions, such as the long duration exposure facility (LDEF) [e.g. 4, 5], and opportunistic analyses of returned surfaces, such as solar cells and radiator panel from the Hubble Space Telescope [e.g. 6-9]. For many impact features it has been very time consuming, difficult or even impossible to give unambiguous attribution of particle origin due to the nature of the collection surface. Consequently, we lack significant and important information for both populations, but especially orbital debris. Whilst there is general agreement as to particle origins between studies of smaller grain sizes impacted on different surfaces [e.g. 7, 9], despite efforts [e.g. 9, 10], the origins for those impact features between 200 μm and 2 mm in size remains ambiguous – hence there remains uncertainty as to how to fill an important gap in our knowledge of the particle population. The Orbital Dust Impact Experiment (ODIE) is a dedicated, passive dust collector that we have designed to verify and understand the flux and origins of these particles. By exposing in low Earth orbit for a period of at least 1 year and returning to Earth for analysis, it will enable the unambiguous identification of both micrometeoroid and orbital debris particles over size ranges including 200 μm to 2 mm. This paper introduces our design and potential deployment options, as well as details of the analyses that would need to be performed upon its return.