The Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) on the New Horizons Mission

Abstract

The Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) comprises the hardware and accompanying science investigation on the New Horizons spacecraft to measure pick-up ions from Pluto's outgassing atmosphere. To the extent that Pluto retains its characteristics similar to those of a "heavy comet" as detected in stellar occultations since the early 1980s, these measurements will characterize the neutral atmosphere of Pluto while providing a consistency check on the atmospheric escape rate at the encounter epoch with that deduced from the atmospheric structure at lower altitudes by the ALICE, REX, and SWAP experiments on New Horizons. In addition, PEPSSI will characterize any extended ionosphere and solar wind interaction while also characterizing the energetic particle environment of Pluto, Charon, and their associated system. First proposed for development for the Pluto Express mission in September 1993, what became the PEPSSI instrument went through a number of development stages to meet the requirements of such an instrument for a mission to Pluto while minimizing the required spacecraft resources. The PEPSSI instrument provides for measurements of ions (with compositional information) and electrons from 10s of keV to ~1 MeV in a 120° x 12° fan-shaped beam in six sectors for 1.5 kg and ~2.5 W.

The Energetic Particle Detector (EPD) Investigation and the Energetic Ion Spectrometer (EIS) for the Magnetospheric Multiscale (MMS) Mission

“…An example of a TOF × E matrix and how it separates different mass species is shown in the left panel of Fig. 13 from the New Horizons PEPSSI instrument at Jupiter (McNutt et al 2008). Lower-energy ion fluxes are measured using TOF-only measurements (the TOF × Pulse Height method); detection of MCP pulse height provides a coarse indication of low-energy particle mass.…”

“…The Johns Hopkins APL has generated and flown numerous TOF × E instruments, generally including SSD-based sensors, on numerous spacecraft. The list includes the Earthorbiting AMPTE CCE MEPA instrument (McEntire et al 1985) and Geotail EPIC instrument (Williams et al 1994), the Jupiter-orbiting Galileo EPD instrument (Williams et al 1992), and the New Horizons PEPSSI instrument now on its way to Pluto (McNutt et al 2008). Instruments that have used the TOF × PH method include the Earth-orbiting IMAGE HENA instrument (Mitchell et al 2003) and the Saturn-orbiting Cassini MIMI INCA instrument (Krimigis et al 2004).…”

Location, structure, and motion of Jupiter's dusk magnetospheric boundary from ∼1625 to 2550 RJ

“…The observations analyzed in this study were made with the RPA and deflector off. SWAP had a few data gaps during this encounter owing to spacecraft outages and cycling of SWAP power and the magnetopause crossings identified during these gaps were made by using time‐of‐flight (TOF) observations from the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) on NH [ McNutt et al , 2008].…”

Jovian deep magnetotail composition and structure

“…Energetic particle measurements were also made over the New Horizons tail passage by the Pluto Energetic Particle Spectrometer Science Investigation (PEPPSI) instrument [ McNutt et al ., ]. Energetic particle observations [ McNutt et al ., ; Haggerty et al ., ; Hill et al ., ; Kollmann et al ., ] collectively showed multiple species, compositional variation, velocity dispersions, intermittent ~3 day periodicities, and particle anisotropies.…”