Characterizing Europa’s subsurface ocean is essential for assessing Europa’s habitability. The suite of instruments on the Europa Clipper spacecraft will, among others, magnetically sound Europa’s interior by measuring the ocean’s induced magnetic field. This magnetic field is generated in response to the Jovian time-varying magnetic environment in which Europa is immersed. However, the dynamic magnetized plasma flow of the Jovian magnetosphere creates electrical currents that give rise to magnetic perturbations near Europa. These perturbations complicate the interpretation of the induction signal, and hence the characterization and inferences on potential habitability. Thus, characterization of the ocean by magnetic sounding requires an accurate characterization of the plasma as it flows across Europa. We present the Plasma Instrument for Magnetic Sounding (PIMS), the instrument for the Europa Clipper mission that will measure the plasma contribution to the magnetic field perturbations sensed by the Europa Clipper Magnetometer. PIMS is composed of four Faraday Cup plasma spectrometers that use voltage-biased gridded apertures to dissect the space plasmas that they encounter. The instrument uses sensitive preamplifiers and processing electronics to measure the current that results when charged particles strike the instrument’s metal collector plates, thus enabling a measure of the plasma characteristics near Europa to produce a more accurate magnetic sounding of Europa’s subsurface ocean. PIMS consists of two sensors: one placed near the top of the Europa Clipper spacecraft and one near the bottom. Each sensor contains two Faraday Cups with a 90° full-width field-of-view. The sensors were specifically designed to withstand the Europa environment, measure both ions and electrons, and have two separate voltage ranges intended to analyze the magnetospheric and ionospheric environments, respectively. In this paper, we describe the scientific motivation for this experiment, the design considerations for the PIMS instrument, the details of the ground calibration, and other details pertinent to understanding the scientific data retrieved by PIMS.

Earth and Space Science Open Archive This is a preprint and has not been peer reviewed. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing an older version [v2]Go to new versionGalileo/EPD user guideAuthorsPeterKollmanniDChristopherParanicasiDALaggiDEliasRoussosiDZ HLee-PayneMKustereriDDSmithNorbertKruppJVandegriffiDSee all authors Peter KollmanniDCorresponding Author• Submitting AuthorJohns Hopkins University Applied Physics LaboratoryiDhttps://orcid.org/0000-0002-4274-9760view email addressThe email was not providedcopy email addressChristopher ParanicasiDJohns Hopkins University Applied Physics LaboratoryiDhttps://orcid.org/0000-0002-4391-8255view email addressThe email was not providedcopy email addressA LaggiDMax Planck Insitute for Solar System ResearchiDhttps://orcid.org/0000-0003-1459-7074view email addressThe email was not providedcopy email addressElias RoussosiDMax Planck Institute for Solar System ResearchiDhttps://orcid.org/0000-0002-5699-0678view email addressThe email was not providedcopy email addressZ H Lee-PayneAberytwyth Universityview email addressThe email was not providedcopy email addressM KustereriDJohns Hopkins University Applied Physics LaboratoryiDhttps://orcid.org/0000-0002-7943-1852view email addressThe email was not providedcopy email addressD SmithJohns Hopkins University Applied Physics Laboratoryview email addressThe email was not providedcopy email addressNorbert KruppMax Planck Insititute for Solar System Researchview email addressThe email was not providedcopy email addressJ VandegriffiDJohns Hopkins University Applied Physics LaboratoryiDhttps://orcid.org/0000-0002-0781-1565view email addressThe email was not providedcopy email address

Suprathermal ions form from interstellar gas that is first ionized into pickup ions and then accelerated to tens and hundreds of keV in energy. The resulting suprathermal ion spectra with hundreds of keV have been previously observed throughout the heliosphere; however, measurements at lower energies, around the pickup ion cutoff energy where they are accelerated from, were limited to <10 au. Here we present a statistical study of suprathermal ions in the keV to hundred keV energy range. We use the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on the New Horizons spacecraft, which recorded observations at a wide range of heliocentric distances, and compare these measurements to charge energy mass spectrometer (CHEMS) observations on Cassini , which cruised to and remained at Saturn. We find that the power-law exponents of suprathermal ion intensity over energy are between −1 and −2, change abruptly close to discontinuities that are likely corotating merged interaction regions, correlate with the solar wind bulk speed, and show a long-term evolution on the timescale of the solar cycle. The independent measurements from New Horizons and Cassini are consistent, confirming the first fully calibrated measurements from the New Horizons /PEPSSI instrument.

The Galileo mission was the first to orbit Jupiter and lasted from 1995 to 2003. Its data set is unique even compared to contemporary data from the Juno mission since Galileo had an equatorial orbit, as it is necessary to sample equatorially mirroring particles. Galileo also had several close moon flybys. It carried instrumentation designed to provide measurements of >MeV electrons. Different to for example optical instruments that can also respond to such particles, an instrument designed to measure radiation is much more straightforward to calibrate. Here we describe Galileo’s EPD suite (Energetic Particle Detector) and its measurements. EPD measures energetic charged particles roughly in the energy range of tens of keV to tens of MeV while distinguishing particle species. This document fills in gaps in the EPD documentation and summarizes already published information. We describe the content of the newly delivered PDS data and how the data has been processed. At the end we also show sample data, explain typical features and possible pitfalls.

We augment the heliospheric network of galactic cosmic ray (GCR) monitors using 2012–2017 penetrating radiation measurements from the New Horizons (NH) Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI), obtaining intensities of ≳75 MeV particles. The new, predominantly GCR observations provide critical links between the Sun and Voyager 2 and Voyager 1 (V2 and V1), in the heliosheath and local interstellar medium (LISM), respectively. We provide NH, Advanced Composition Explorer (ACE), V2, and V1 GCR observations, using them to track solar cycle variations and short-term Forbush decreases from the Sun to the LISM, and to examine the interaction that results in the surprising, previously reported V1 LISM anisotropy episodes. To investigate these episodes and the hitherto unexplained lagging of associated in situ shock features at V1, propagating disturbances seen at ACE, NH, and V2 were compared to V1. We conclude that the region where LISM magnetic field lines drape around the heliopause is likely critical for communicating solar disturbance signals upstream of the heliosheath to V1. We propose that the anisotropy-causing physical process that suppresses intensities at ∼90° pitch angles relies on GCRs escaping from a single compression in the draping region, not on GCRs trapped between two compressions. We also show that NH suprathermal and energetic particle data from PEPSSI are consistent with the interpretation that traveling shocks and corotating interaction region (CIR) remnants can be distinguished by the existence or lack of Forbush decreases, respectively, because turbulent magnetic fields at local shocks inhibit GCR transport while older CIR structures reaching the outer heliosphere do not.

Pluto energies of a few kiloelectron volts and suprathermal ions with tens of kiloelectron volts and above. We measure this population using the Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) instrument on board the New Horizons spacecraft that flew by Pluto in 2015. Even though the measured ions have gyroradii larger than the size of Pluto and the cross section of its magnetosphere, we find that the boundary of the magnetosphere is depleting the energetic ion intensities by about an order of magnitude close to Pluto. The intensity is increasing exponentially with distance to Pluto and reaches nominal levels of the interplanetary medium at about 190R(P) distance. Inside the wake of Pluto, we observe oscillations of the ion intensities with a periodicity of about 0.2 hr. We show that these can be quantitatively explained by the electric field of an ultralow-frequency wave and discuss possible physical drivers for such a field. We find no evidence for the presence of plutogenic ions in the considered energy range.

New Horizons unveils the Pluto system In July 2015, the New Horizons spacecraft flew through the Pluto system at high speed, humanity's first close look at this enigmatic system on the outskirts of our solar system. In a series of papers, the New Horizons team present their analysis of the encounter data downloaded so far: Moore et al. present the complex surface features and geology of Pluto and its large moon Charon, including evidence of tectonics, glacial flow, and possible cryovolcanoes. Grundy et al. analyzed the colors and chemical compositions of their surfaces, with ices of H 2 O, CH 4 , CO, N 2 , and NH 3 and a reddish material which may be tholins. Gladstone et al. investigated the atmosphere of Pluto, which is colder and more compact than expected and hosts numerous extensive layers of haze. Weaver et al. examined the small moons Styx, Nix, Kerberos, and Hydra, which are irregularly shaped, fast-rotating, and have bright surfaces. Bagenal et al. report how Pluto modifies its space environment, including interactions with the solar wind and a lack of dust in the system. Together, these findings massively increase our understanding of the bodies in the outer solar system. They will underpin the analysis of New Horizons data, which will continue for years to come. Science , this issue pp. 1284 , 10.1126/science.aad9189 , 10.1126/science.aad8866 , 10.1126/science.aae0030 , & 10.1126/science.aad9045

Solar Probe Plus (SPP) will be the first spacecraft to fly into the low solar corona. SPP’s main science goal is to determine the structure and dynamics of the Sun’s coronal magnetic field, understand how the solar corona and wind are heated and accelerated, and determine what processes accelerate energetic particles. Understanding these fundamental phenomena has been a top-priority science goal for over five decades, dating back to the 1958 Simpson Committee Report. The scale and concept of such a mission has been revised at intervals since that time, yet the core has always been a close encounter with the Sun. The mission design and the technology and engineering developments enable SPP to meet its science objectives to: (1) Trace the flow of energy that heats and accelerates the solar corona and solar wind; (2) Determine the structure and dynamics of the plasma and magnetic fields at the sources of the solar wind; and (3) Explore mechanisms that accelerate and transport energetic particles. The SPP mission was confirmed in March 2014 and is under development as a part of NASA’s Living with a Star (LWS) Program. SPP is scheduled for launch in mid-2018, and will perform 24 orbits over a 7-year nominal mission duration. Seven Venus gravity assists gradually reduce SPP’s perihelion from 35 solar radii ( $R_{S}$ ) for the first orbit to ${<}10~R_{S}$ for the final three orbits. In this paper we present the science, mission concept and the baseline vehicle for SPP, and examine how the mission will address the key science questions