Modeling Meteoroid Impacts on the Juno spacecraft

TL;DR

This study compares observed star tracker events on Juno to dynamical meteoroid models and finds that the events are unlikely caused by interplanetary dust impacts, challenging previous assumptions about their origin.

Contribution

The paper provides a detailed comparison between observed impact events on Juno and model predictions, demonstrating a mismatch and ruling out zodiacal dust as the primary source.

Findings

Dynamical models do not match observed event rates.

Star tracker events are unlikely caused by zodiacal dust impacts.

Mars-origin dust cannot explain the observed event variations.

Abstract

Events which meet certain criteria from star tracker images onboard the Juno spacecraft have been proposed to be due to interplanetary dust particle impacts on its solar arrays. These events have been suggested to be caused by particles with diameters larger than 10 micrometers. Here, we compare the reported event rates to expected dust impact rates using dynamical meteoroid models for the four most abundant meteoroid/dust populations in the inner solar system. We find that the dust impact rates predicted by dynamical meteoroid models are not compatible with either the Juno observations in terms of the number of star tracker events per day, or with the variations of dust flux on Juno's solar panels with time and position in the solar system. For example, the rate of star tracker events on Juno's anti-sunward surfaces is the largest during a period during which Juno is expected to experience the peak impact fluxes on the opposite, sunward hemisphere. We also investigate the hypothesis of dust leaving the Martian Hill sphere originating either from the surface of Mars itself or from one of its moons. We do not find such a hypothetical source to be able to reproduce the star tracker event rate variations observed by Juno. We conclude that the star tracker events observed by Juno are unlikely to be the result of instantaneous impacts from the Zodiacal Cloud.