Calibration of polyvinylidene fluoride based dust detectors in response to varying grain density and incidence angle

Permanently polarized Polyvinylidene Fluoride (PVDF) films have been used on a variety of spacecraft as in situ dust detectors to measure the size and spatial distributions of micron and sub-micron dust particles. The detectors produce a short electric pulse when impacted by a hypervelocity dust particle. The pulse amplitude depends on the mass and relative speed of the dust grain. This relationship has been studied both empirically and numerically to better understand the film's principle of operation, as well as the effects of film thickness, film temperature, and particle penetration depth. However, little work has been done to constrain the effects of varying particle density and incidence angle despite the frequent occurrence of such configurations in most space-based applications. We present calibrations of non-penetrating impacts on 28 μm thick films at varying incidence angles ranging from 0° to 75° for iron and aluminum particles in the mass and speed range of 10^-12 ≤ m ≤ 10^-8 g and 0.5 ≤ v ≤ 7 km/s, respectively. The study was carried out at the 3 MV dust accelerator laboratory at the University of Colorado at Boulder. The results show that PVDF signals are largely independent of particle density and incidence angle up to 75° for non-penetrating impacts.

Pluto's interaction with its space environment: Solar wind, energetic particles, and dust

The New Horizons spacecraft carried three instruments that measured the space environment near Pluto as it flew by on 14 July 2015. The Solar Wind Around Pluto (SWAP) instrument revealed an interaction region confined sunward of Pluto to within about 6 Pluto radii. The region's surprisingly small size is consistent with a reduced atmospheric escape rate, as well as a particularly high solar wind flux. Observations from the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument suggest that ions are accelerated and/or deflected around Pluto. In the wake of the interaction region, PEPSSI observed suprathermal particle fluxes equal to about 1/10 of the flux in the interplanetary medium and increasing with distance downstream. The Venetia Burney Student Dust Counter, which measures grains with radii larger than 1.4 micrometers, detected one candidate impact in ±5 days around New Horizons' closest approach, indicating an upper limit of <4.6 kilometers(-3) for the dust density in the Pluto system.