Data Set Overview  :   This data set contains Raw data taken by New Horizons  Pluto Energetic Particle Spectrometer Science Investigation  instrument during the PLUTO 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 pitch  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.   During the Pluto 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). For this first PEPSSI delivery  for the Pluto mission phase, this data set includes only the Approach  data plus the subset of the CORE sequence data that was downlinked  through the end of July, 2015. The rest of the Pluto data will be  delivered in future versions of this data set according to the schedule  worked out by the Project and NASA.   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. This dataset includes data from the Approach  phase and from the Pluto encounter on the day around closest approach.   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_PLUTO.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 1.0 of this data set.    Processing  :   The data in this data set were created by a software data  processing pipeline on the Science Operation Center (SOC) at  the Southwest Research Institute (SwRI), Department of Space Studies.  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  | |  | +--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   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  along with the instrument designator that go with each ApID:    ApIDs Data product description/Prefix(es)  : :  0x691 - PEPSSI High Priority Science/PEP  0x692 - PEPSSI Medium Priority Science/PEP  0x693 - PEPSSI Low Priority Science (Up to 500 PHA events)/PEP  0x694 - PEPSSI Low Priority Science (Up to add'l 500 PHA events)/PEP  0x695 - PEPSSI High Priority Science/PEP  0x696 - PEPSSI Medium Priority Science/PEP  0x697 - PEPSSI Low Priority Science (Up to 500 PHA events)/PEP  0x698 - PEPSSI Low Priority Science (Up to add'l 500 PHA events)/PEP    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. The PDS  standards 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.    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-PLUTO-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_PLUTO.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; that is,  some sequences may have failed to execute due to spacecraft events  (e.g. safing) and there will be observations associated with those  sequences. No attempt has been made during the preparation of this  data set to identify if any, or how many, such empty sequences there  are, so it is up to the user to compare the times of the sequences  to the times of the available observations from the INDEX/INDEX.TAB  table 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) over this dataset  is 65.184s.   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-P-PEPSSI-2-PLUTO-V1.0,   may not have corresponding data products in the calibrated data set,   NH-P-PEPSSI-3-PLUTO-V1.0.    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_PLUTO.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, the electron count rates have not changed as expected with  distance from the sun. The team is aware of this and is reviewing  the data.   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 (DOCUMENT/SOC_INST_ICD*.*) and the BTI TABLE file for  more detail.     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  TBD.