DOI: 10.26007/y8pg-xw33
title: New Horizons Pluto Energetic Particle Spectrometer Science Investigation (PEPSSI) Pluto Encounter Raw Data, Version 1.0

description: This data set contains Raw data taken by the 
 New Horizons Pluto Energetic Particle Spectrometer Science Investigation
 (PEPSSI) instrument during the KEM1 ENCOUNTER mission phase. These data 
 were migrated from the PDS3 dataset: NH-P-PEPSSI-2-PLUTO-V3.0.
 
 PEPSSI is a particle telescope and a time-of-flight (TOF) spectrometer that 
 measures ions and electrons over a broad range of energies and 
 angles. Particle composition and energy spectra are measured for H to 
 Fe from ~ 30 keV to ~1 MeV (but not all species are uniquely separated) 
 and for electrons from ~30 keV to 700 keV. PEPSSI comprises a 
 time-of-flight (TOF) section and a solid-state detector (SSD) array 
 that measures particle energy. The combination of measured energy and 
 TOF provides unique particle identification by mass and particle energy 
 depending on the range: for protons from ~30 keV to ~1 MeV; for heavy 
 (CNO) ions from ~80 keV to ~1 MeV. Lower-energy (&gt;3 keV) ion fluxes are 
 measured by TOF only, but without the SSD signal, providing velocity 
 spectra at these energies as well. Due to storage and bandwidth 
 limitations, all event data cannot be stored or telemetered to the 
 ground. Instead, a round-robin algorithm is used to save Energy, TOF, 
 and timing data for select events. The common data products contain 
 these event and summary measurements, accumulated over fixed periods of 
 86,400 seconds, with each period in a single file comprising multiple 
 binary tables.
 
 During the Pluto Charon Encounter mission phase starting in 
 January, 2015, there were several sub-phases: three Approach 
 sub-phases, (AP1, AP2 and AP3); a CORE sequence for the Pluto 
 flyby on 14 July, 2015 (Day Of Year 195), sometimes also referred 
 to as NEP (Near-Encounter Phase); three Departure sub-phases 
 (DP1, DP2, DP3); a Transition sub-phase ending in late October, 2016, 
 closing out the Pluto Encounter mission phase. For this final PEPSSI 
 delivery for the Pluto mission phase, this data set includes the 
 Approach data plus the CORE and Departure sequences' data, as well as 
 normal operation and Calibration Campaign data during Transition, and 
 has all data downlinked through the end of October, 2016. 
 
 During the Approach phase, PEPSSI performed functional tests including 
 a memory refresh, and otherwise operated as normal, turning off and on 
 around spacecraft trajectory correction maneuvers, and taking data 
 during a series of plasma rolls, on DOY 107, 115, 121, 128, 148, 156, 
 and 176. There were two other dedicated SWAP and PEPSSI rolls on DOY 
 163 and 171. PEPSSI was powered on and collecting data throughout the 
 encounter time frame. 
 
 PEPSSI was generally turned on and taking data for the Departure and 
 Transition sub-phases, the exceptions being when PEPSSI was turned off 
 during spacecraft events such as 3-axis operations and trajectory 
 correction maneuvers. 
 
 Due to a spacecraft safing event on 04 July, 2015 (DOY 185), the 
 balance of the science load from then-executing 15184 sequence 
 (nominal start time on DOY 184 in 2015) was sacrificed to ensure the 
 15188 CORE load with the flyby sequence could be loaded onto the 
 spacecraft and started on time. As a result, there is a gap in the 
 PEPSSI data from approximately DOY 186 to DOY 188. 
 
 Labels were redesigned during migration using the .FIT header and PDS3 .LBL
 files, but the data files are unchanged from their PDS3 version.