Data Set Overview  :   This data set contains Calibrated data taken by New Horizons  Pluto Energetic Particle Spectrometer Science Investigation  instrument during the PLUTOCRUISE mission phase.   PEPSSI (Pluto Energetic Particles Spectrometer Science Investigation)  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 (>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. The documentation provided with this data set describes  the data format.    PEPSSI Data Summary  :   During the Annual Check-out (ACO) periods 1-4 in 2007 though 2010,  PEPSSI performed a combination of calibration operations, table and  macro loads, and statistics gathering, which may be suitable for  science.   From 2011 through 2014, PEPSSI collected mostly science data during  hibernation, with breaks for checkouts during ACO periods 5-8.    PEPSSI Data Details  :   The calibration operations ranged from functional checks, which run  the instrument for a short period to see if operations are nominal,  to operations in which the New Horizons spacecraft attitude is set  to aim the PEPSSI apertures in specified directions to permit  angular calibration akin to flat fielding for remote sensing  instruments. Table loads were performed to make improvements, e.g.  to PEPSSI's capability to identify particle species, and macro  loads were done to simplify operations so that a single spacecraft  command can execute a large number of PEPSSI activities within the  instrument, such as a power up sequence that we wish to be  identical whenever the instrument is turned on. The statistics  gathering activities were done primarily to populate the  time-of-flight vs. energy histograms. Those histograms are needed  to understand the PEPSSI mass identification response at Pluto, but  these periods also offer valuable interplanetary science data.   Almost all PEPSSI data in this data set are part of calibration,  functional tests and instrument checkout operations. However,  during periods when there were no interfering operations, such as  calibration operations or table loads, the term 'potential' is used  here to alert the user to periods where major sources of conflict  are lacking and the data taken may be scientifically useful. This  does not obviate the need to carefully examine all the spacecraft  and instrument states coincident with the data period under study,  for example the spacecraft attitude and background particles in a  given energy/species channel. The following is an overview of the  data taken during the four ACOs in this delivery.   In ACO-1, which ran from 2007/257-303 for PEPSSI, the major  operations included table loads, a diagnostic mode test, statistics  gathering, a full-sky scan activity, anisotropy test #1 for angular  calibration, and solid state detector (SSD) tests. The potential  periods for science data include the following periods, given at  daily granularity: 2007/257-258, 259-260, 278-282, and 300-303.   In ACO-2, which ran from 2008/276-341 for PEPSSI, the major  operations included table loads, a diagnostic mode test, statistics  gathering, start and stop discriminator threshold scans, anisotropy  test #2, a scan of the Sun through the PEPSSI field of view, a  macro load, and a memory refresh. The potential periods for  science data include the following periods, given at daily  granularity: 2008/276,278-280,282-283,284-287, and 303-341.   In ACO-3, the instrument function was tested by running PEPSSI for  24 hours on 2009/223. All data taken during this period are  potential science data.   Nearly all data taken during ACO-4 (2010/162-207) are potential  science data. Activities included a scan of the Sun across the  PEPSSI field of view, a memory refresh and statistics gathering.  The non-science activities are the sun scan, which took place from  2010/176 23:11:00 to 177 00:23:23, including two sun scans and set  up slews, and the 2010/184 20:05 EEPROM memory refresh.   From 2011 through 2014, analysis of spacecraft power margins  indicated that PEPSSI could operate during hibernation; prior to  that time PEPSSI was normally off during hibernation. So after  2010, PEPSSI collected science data for most of the rest of the  Pluto Cruise mission phase, with breaks for ACO periods 5-8 for  instrument monitoring, testing and characterization.   Every observation provided in this data set was taken as a part of a  particular sequence. A list of these sequences has been provided in  file DOCUMENT/SEQ_PEPSSI_PLUTOCRUISE.TAB.  N.B. Some sequences provided may have no corresponding observations.   For a list of observations, refer to the data set index table. This  is typically INDEX.TAB initially in the INDEX/ area of the data set.  There is also a file SLIMINDX.TAB in INDEX/ that summarizes key  information relevant to each observation, including which sequence  was in effect and what target was likely intended for the  observation.    Version  :   This is VERSION 2.0 of this data set.   The pipeline (see Processing below) was re-run on these data for each  version since the first (V1.0). As a result, ancillary information,  such as observational geometry and time (SPICE), may be updated.  This will affect, for example, the calibration of the data if parameters such as the velocity or orientation of the target relative to the  instrument, or the recorded target itself, have changed.   See the following sections for details of what has changed over each  version since the first (V1.0). Note that even if this is not a  calibrated data set, the calibration changes are listed as the data  will have been re-run and there will be updates to the calibration  files, to the documentation (Science Operations Center - Instrument  Interface Control Document: SOC_INST_ICD) and to the steps required  to calibrate the data.    PEPSSI updates for Pluto Cruise  Data Sets V2.0  :   The previous Pluto Cruise data sets' deliveries (V1.0) went  through peer review in December, 2014. When subsequent versions  of those data sets were being delivered, some with additional data  (from August, 2014 through January, 2015) before all of those  previous liens were resolved, the previous data sets were left as  is, with those liens folded into the newer data sets.   New observations added with this version (V2.0) include ongoing  cruise observations from August, 2014 through January, 2015.   Other changes for this version were re-running of the ancillary  data in the data product, updated geometry from newer SPICE  kernels, minor editing of the documentation, catalogs, etc., and  resolution of liens from the December, 2014 review, plus those  from the May, 2016 review of the Pluto Encounter data sets.    Processing  :   The data in this data set were created by a software data  processing pipeline on the Science Operations Center (SOC) at  the Southwest Research Institute (SwRI), Department of Space Operations. This SOC pipeline assembled data as FITS files from raw telemetry  packets sent down by the spacecraft and populated the data labels  with housekeeping and engineering values, and computed geometry  parameters using SPICE kernels. The pipeline did not resample  the data.    Data  :   The observations in this data set are stored in data files using  standard Flexible Image Transport System (FITS) format. Each FITS  file has a corresponding detached PDS label file, named according  to a common convention. The FITS files may have image and/or table  extensions. See the PDS label plus the DOCUMENT files for a  description of these extensions and their contents.   This Data section comprises the following sub-topics:   - Filename/Product IDs  - Instrument description  - Other sources of information useful in interpreting these Data  - Visit Description, Visit Number, and Target in the Data Labels    Filename/Product IDs  --------------------   The filenames and product IDs of observations adhere to a  common convention e.g.   PEP_0123456789_0X691_ENG.FIT  ^^^ ^^^^^^^^^^ ^^^^^ ^^^\__/  | | | | ^^  | | | | |  | | | | +--File type (includes dot)  | | | | - .FIT for FITS file  | | | | - .LBL for PDS label  | | | | - not part of product ID  | | | |  | | | +--ENG for CODMAC Level 2 data  | | | SCI for CODMAC Level 3 data  | | |  | | +--Application ID (ApID) of the telemetry data  | | packet from which the data come  | | N.B. ApIDs are case-insensitive  | |  | +--MET (Mission Event Time) i.e. Spacecraft Clock  |  +--Instrument designator    Note that, depending on the observation, the MET in the data filename  and in the Product ID may be similar to the Mission Event Time (MET)  of the actual observation acquisition, but should not be used as an  analog for the acquisition time. The MET is the time that the data are  transferred from the instrument to spacecraft memory and is therefore  not a reliable indicator of the actual observation time. The PDS label  and the index tables are better sources to use for the actual timing of  any observation. The specific keywords and index table column names for which to look are   * START_TIME  * STOP_TIME  * SPACECRAFT_CLOCK_START_COUNT  * SPACECRAFT_CLOCK_STOP_COUNT    Instrument Instrument designators ApIDs **  : : :  PEPSSI PEP 0X691 - 0X698 *   * Not all values in this range are in this data set  ** ApIDs are case insensitive   There are other ApIDs that contain housekeeping values and  other values. See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*)  for more details.    Here is a summary of the types of files generated by each ApID  (N.B. ApIDs are case-insensitive) along with the instrument  designator that go with each ApID:    ApIDs Data product description/Prefix(es)  : :  0x691 - PEPSSI High Priority Science (long integration)  0x692 - PEPSSI Medium Priority Science (short integration)  0x693 - PEPSSI Low Priority Science (Up to 500 PHA events)  0x694 - PEPSSI Low Priority Science (Up to 500 PHA events)  0x695 - PEPSSI High Priority Science Diagnostic Mode data  0x696 - PEPSSI Medium Priority Science Diagnostic Mode data  0x697 - PEPSSI Diagnostic Mode Event data  0x698 - PEPSSI Diagnostic Mode Event data   For historical reasons, PEPSSI products always use an ApID of '0x691'  in the filename. Each product actually contains all the data types  (ApIDs) available for that day.   ApIDs '0x693' and '0x694' are combined during ground processing.  So are ApIDs '0x697' and '0x698'.    Instrument description  ----------------------   Refer to the following files for a description of this instrument.   CATALOG   PEPSSI.CAT   DOCUMENTS   PEPSSI_SSR.*  SOC_INST_ICD.*  NH_PEPSSI_V###_TI.TXT (### is a version number)    Other sources of information useful in interpreting these Data  --------------------------------------------------------------   Refer to the following files for more information about these data   NH Trajectory tables:   /DOCUMENT/NH_MISSION_TRAJECTORY.* - Heliocentric   PEPSSI Field Of View definitions:   /DOCUMENT/NH_FOV.*  /DOCUMENT/NH_PEPSSI_V###_TI.TXT     Visit Description, Visit Number, and Target in the Data Labels  ---------------------------------------------------------------   The observation sequences were defined in Science Activity Planning  (SAP) documents, and grouped by Visit Description and Visit Number.  The SAPs are spreadsheets with one Visit Description & Number per row.  A nominal target is also included on each row and included in the data  labels, but does not always match with the TARGET_NAME field's value in  the data labels. In some cases, the target was designated as RA,DEC  pointing values in the form ``RADEC:123.45,-12.34'' indicating Right  Ascension and Declination, in degrees, of the target from the  spacecraft in the Earth Equatorial J2000 inertial reference frame.  This indicates either that the target was either a star, or that the  target's ephemeris was not loaded into the spacecraft's attitude and  control system which in turn meant the spacecraft could not be pointed  at the target by a body identifier and an inertial pointing value had  to be specified as Right Ascension and Declination values. PDS-SBN  practices do not allow putting a value like RADEC:... in the PDS  TARGET_NAME keyword's value. In those cases the PDS TARGET_NAME value  is set to CALIBRATION. TARGET_NAME may be N/A (Not Available or Not  Applicable) for a few observations in this data set; typically that  means the observation is a functional test so N/A is an appropriate  entry for those targets, but the PDS user should also check the  NEWHORIZONS:OBSERVATION_DESC and NEWHORIZONS:SEQUENCE_ID keywords in  the PDS label, plus the provided sequence list (see Ancillary Data  below) to assess the possibility that there was an intended target.    Ancillary Data  :   The geometry items included in the data labels were computed  using the SPICE kernels archived in the New Horizons SPICE  data set, NH-X-SPICE-6-PLUTOCRUISE-V1.0.   Every observation provided in this data set was taken as a part of a  particular sequence. A list of these sequences has been provided in  file DOCUMENT/SEQ_PEPSSI_PLUTOCRUISE.TAB. In addition, the  sequence identifier (ID) and description are included in the PDS label  for every observation. N.B. While every observation has an associated  sequence, every sequence may not have associated observations. Some  sequences may have failed to execute due to spacecraft events (e.g.  safing). No attempt has been made during the preparation of this data  set to identify such empty sequences, so it is up to the user to  compare the times of the sequences to the times of the available  observations from INDEX/INDEX.TAB to identify such sequences.    Time  :   There are several time systems, or units, in use in this dataset:  New Horizons spacecraft MET (Mission Event Time or Mission Elapsed  Time), UTC (Coordinated Universal Time), and TDB Barycentric  Dynamical Time.   This section will give a summary description of the relationship  between these time systems. For a complete explanation of these  time systems the reader is referred to the documentation  distributed with the Navigation and Ancillary Information  Facility (NAIF) SPICE toolkit from the PDS NAIF node, (see  http://naif.jpl.nasa.gov/).   The most common time unit associated with the data is the spacecraft  MET. MET is a 32-bit counter on the New Horizons spacecraft that  runs at a rate of about one increment per second starting from a  value of zero at   19.January, 2006 18:08:02 UTC   or   JD2453755.256337 TDB.   The leapsecond adjustment (DELTA_ET : ET - UTC) was 65.184s at  NH launch, and the first three additional leapseconds occured  in at the ends of December, 2009, June, 2012 and June, 2015.  Refer to the NH SPICE data set, NH-J/P/SS-SPICE-6-V1.0, and the  SPICE toolkit docmentation, for more details about leapseconds.   The data labels for any given product in this dataset usually  contain at least one pair of common UTC and MET representations  of the time at the middle of the observation. Other portions  of the products, for example tables of data taken over periods  of up to a day or more, will only have the MET time associated  with a given row of the table.   For the data user's use in interpreting these times, a reasonable  approximation (+/- 1s) of the conversion between Julian Day (TDB)  and MET is as follows:   JD TDB : 2453755.256337 + ( MET / 86399.9998693 )   For more accurate calculations the reader is referred to the  NAIF/SPICE documentation as mentioned above.    Reference Frame  :    Geometric Parameter Reference Frame  -----------------------------------   Earth Mean Equator and Vernal Equinox of J2000 (EMEJ2000) is the  inertial reference frame used to specify observational geometry items  provided in the data labels. Geometric parameters are based on best  available SPICE data at time of data creation.    Epoch of Geometric Parameters  -----------------------------   All geometric parameters provided in the data labels were computed at  the epoch midway between the START_TIME and STOP_TIME label fields.     Software  :   The observations in this data set are in standard FITS format  with PDS labels, and can be viewed by a number of PDS-provided  and commercial programs. For this reason no special software is  provided with this data set.    Contact Information  :   For any questions regarding the data format of the archive,  contact   New Horizons PEPSSI Principal Investigator:   Ralph McNutt, Jr., Johns Hopkins Univ., Applied Physics Lab   Ralph McNutt, Jr.   Johns Hopkins University  Applied Physics Laboratory  Space Department  11100 Johns Hopkins Road  Room MP3-E116  Laurel, MD 20723  USA

Confidence Level Overview  :  During the processing of the data in preparation for  delivery with this volume, the packet data associated with each  observation were used only if they passed a rigorous verification  process including standard checksums.   In addition, raw (Level 2) observation data for which adequate  contemporary housekeeping and other ancillary data are not available  may not be reduced to calibrated (Level 3) data. This issue is raised  here to explain why some data products in the raw data set,   NH-X-PEPSSI-2-PLUTOCRUISE-V2.0,   may not have corresponding data products in the calibrated data set,   NH-X-PEPSSI-3-PLUTOCRUISE-V2.0.    Data coverage and quality  :  Every observation provided in this data set was taken as a part of a  particular sequence. A list of these sequences has been provided in  file DOCUMENT/SEQ_PEPSSI_PLUTOCRUISE.TAB. N.B. Some sequences  provided may have zero corresponding observations.   Refer to the Confidence Level Overview section above for a summary  of steps taken to assure data quality.   For PEPSSI, electron detector channels are dominated by cosmic rays  in post-Jupiter mission phases.   The PEPSSI data are considered suspect for the first forty  minutes after an instrument power-on event, called a Bad Time  Interval (BTI); this file lists those time windows. The entire  Post-launch commissioning mission phase is also considered a  BTI.   See the Science Operations Center - Instrument Interface Control  Document (ICD - found at DOCUMENT/SOC_INST_ICD*.*) and the BTI TABLE  file for more detail.   The PEPSSI Time Of Flight only (TOF-only) Pulse Height Analysis (PHA)  event data may show differences in the 'N2 data' and 'N3 data' taken  simultaneously but using different collection algorithms. Refer to  the instrument description in the PEPSSI instrument catalog  (PEPSSI.CAT) under 'Data sampling and priority for TOF-only data'  in the 'Operational modes' section.   Some subset of the PHA event data is noise or other instrumental  artifacts. PHA events with parameters outside the stated instrument  sensitivity limits (see the SPECIFICATIONS section in the PEPSSI  instrument catalog file) should be ignored, or, at the very least,  used with extreme caution.   It should be noted that the Primary HDU and the first 5 extension  HDUs (the Image HDUs containing spectrograms) of the level 3 data  are 'quick-look' or 'browse' products only. They are constructed  with one minute averages for the whole mission, so that, if the data  collection period (the DT in the table in the FLUX extension) is not  an even multiple or factor of 1 minute, the spectrogram image will  exhibit aliasing artifacts. Further, the second extension, the  Helium spectrogram includes the Alpha source channels (see above).  In short, the Image HDUs in the level 3 data are not for scientific  use but for browsing or quick-look purposes and for researchers to  determine if they are able to correctly read the data in the table  extensions.   Data at higher resolution, up to 1 second for the Pluto Encounter  time period, can be found in the Flux and PHA Data HDUs. Please see  the ICD, section 11, and specifically sections 11.2 and 11.4, for  details regarding interpreting rates and the timing of events.   Please see the 'Data Validity' section of PEPSSI.CAT for details  regarding information on channels which should be excluded from  analysis.     Observation descriptions in this data set catalog  :   Some users will expect to find descriptions of the observations  in this data set here, in this Confidence Level Note. This data  set follows the more common convention of placing those  descriptions under the Data Set Description (above, if the user is  reading this in the DATASET.CAT file) of this data set catalog.    Caveat about TARGET_NAME in PDS labels and observational intent  :    A fundamental truth of managing data from some spacecraft missions  is that the intent of any observation is not suitable for insertion  into the command stream sent to the spacecraft to execute that  observation. As a result, re-attaching that intent to the data  that are later downlinked is problematic at best. For New Horizons  that task is made even more difficult as the only meta-data that  come down with the observation is the unpredictable time of the  observation. The task is made yet even more difficult because  uplink personnel, who generate the command sequences and initially  know the intent of each observation, are perpetually under  deadlines imposed by orbital mechanics and can rarely be spared for  the time-intensive task of resolving this issue.   To make a long story short, the downlink team on New Horizons has  created an automated system to take various uplink products, decode  things like Chebyshev polynomials in command sequences representing  celestial body ephemerides for use on the spacecraft to control  pointing, and infer from those data what the most likely intended  target was at any time during the mission. This works well during  flyby encounters and less so during cruise phases and hibernation.   The point to be made is that the user of these PDS data needs to  be cautious when using the TARGET_NAME and other target-related  parameters stored in this data set. This is less an issue for the  plasma and particle instruments, more so for pointing instruments.  To this end, the heliocentric ephemeris of the spacecraft, the  spacecraft-relative ephemeris of the inferred target, and the  inertial attitude of the instrument reference frame are provided  with all data, in the J2000 inertial reference frame, so the user  can check where that target is in the Field Of View (FOV) of the  instrument. Furthermore, for pointing instruments with one or more  spatial components to their detectors, a table has been provided  in the DOCUMENT/ area with XY (two-dimensional) positions of each  inferred target in the primary data products. If those values are  several thousand pixels off of a detector array, it is a strong  indication that the actual target of that observation is something  other than the inferred target, or no target at all e.g. dark sky.    Review  :  This dataset was peer reviewed and certified for scientific use on  2017-03-29.