Anatomy of a comet tail transited by the Juno spacecraft en route to Jupiter

A star camera aboard the Juno spacecraft traveling from Earth to Jupiter serendipitously recorded the impact of interplanetary dust particles (IDPs) by imaging bits of the spacecraft ejected from the IDP impact sites. In essence, the Juno spacecraft, with its expansive ~60 m2 of solar arrays, served as a dust detector with orders of magnitude more aperture than dedicated dust detectors specifically designed and flown to detect dust impacts. Consequently, Juno recorded many impacts with the larger (few to tens of micro-meters) and less numerous IDPs that populate the inner solar system, establishing for the first time their distribution and source (Jorgensen et al., 2020). Six months prior to its arrival at Jupiter, the Juno spacecraft recorded a singular burst of interplanetary dust particle impacts attributed to passage through the extended tail of a comet. That comet has now been identified as the recently discovered Jupiter family comet P/2019 S3 Pan-STARRS (SPKID 1003641), affording a unique opportunity to characterize the dynamical motion of the comet’s dust tail. Dust impacting the spacecraft orbits under the influence of radiation pressure forces and gravity (ratio b = ~0.05), escaping the comet nucleus ~2 years prior to impact on the spacecraft and ~1 year post comet perihelion. Impacting dust, with an implied radius of ~10 mm, escaped the comet nucleus with a radial velocity of ~120 ms-1, appropriate to a comet with a radius of a few km.