Data Set Overview
      =================

      This data set includes the complete set of New Horizons (NH) SPICE
      data files (``kernel files''), which can be accessed using SPICE
      software. The SPICE data contain geometric and other ancillary
      information needed to recover the full value of the science
      instrument data. In particular SPICE kernels provide spacecraft
      and planetary ephemerides, instrument mounting alignments,
      spacecraft orientation, and data needed for relevant time
      conversions.

      Generally, these kernels are provided by the Project and distributed
      by Mission Operation (MOPs) under configuration control.  Since those
      kernels are focused on mission success, they are not always adeqaute
      for data analysis.  The Science Operation Center (SOC) has created
      additional kernels to enhance running the automated data pipeline on
      downlinked data (for example, identifying and locating a target in
      an observation when that observation was planned using only inertial
      pointing determined manually), with the caveat that such kernels will
      not be used by MOPs.

      This data set is contained on a single virtual volume, NHSP_1000,
      including data from all mission phases and covering from launch,
      2006 JAN 19, through the end time of the latest spacecraft
      trajectory file supplied in the data set. Until the end of the
      spacecraft lifespan this data set will be accumulating with new
      data added approximately six months after completion of each
      major mission phase, and there may also be additional deliveries
      at the discretion of the Project.


      Data Types (SPICE kernel types)
      ===============================

      SPK kernels contain ephemerides for spacecraft, planets,
      satellites, comets and asteroids as well as for moving or fixed
      spacecraft and instrument structures. They provide position and
      velocity, given in a Cartesian reference frame. SPK files are
      located under the ``data/spk'' directory of this data set.

      PCK kernels contain certain physical, dynamical and
      cartographic constants for target bodies, such as size and shape
      specifications, and the orientation of the spin axis and prime
      meridian. PCK files are located under the ``data/pck'' directory
      of this data set.

      IK kernels (Instrument description kernels) give descriptive and
      operational data peculiar to a particular scientific instrument,
      such as internal timing relative to the spacecraft clock and
      field-of-view model parameters. IK files are located under the
      ``data/ik'' directory of this data set.

      CK kernels describe pointing, containing a transformation
      traditionally called the C-matrix which is used to determine
      time-tagged pointing (orientation) angles for a spacecraft
      structure upon which science instruments are mounted. CK files
      are located under the ``data/ck'' directory of this data set.

      EK (Events) kernels are derived from the integrated sequence of
      events used to produce actual spacecraft commands. EK files are
      located under the ``data/ek'' directory of this data set.

      LSK (Leapseconds) kernels contain the leapseconds and the values
      of other constants required to perform a transformation between
      Universal Time Coordinated (UTC) and Ephemeris time (ET). LSK
      files are located under the ``data/lsk'' directory of this data
      set.

      SCLK (Spacecraft Clock) kernels contain on-board clock calibration
      data required to perform a mapping between Ephemeris time (ET)
      and spacecraft on-board time (SCLK.) SCLK files are located under
      the ``data/sclk'' directory of this data set.

      FK (Frame Definitions) kernels contain information required to
      define reference frames, sources of frame orientation data and
      connections between these frames and other frames supported
      within the SPICE system. This includes mounting alignment
      information for each instrument. FK files are located under the
      ``data/fk'' directory of this data set.

      DSK (Digital Shape) kernels contain information about the shape
      of the New Horizons mission targets. DSK files are located under
      the ``data/dsk'' directory of this data set.


      Kernel File Details
      ===================

      A brief overview of the different types of New Horizons kernels
      included in this data set is provided in the
      CONFIDENCE_LEVEL_NOTE section of this file while details specific
      to individual files are found in the ``*info.txt'' files in the
      corresponding data directory. The most detailed description of
      the data in each file is provided in metadata included inside the
      file -- in the description area of text kernels or in the comment
      area of binary kernels.


      Software
      ========

      The SPICE Toolkit contains software modules needed to read
      SPICE kernel files. SPICE software is highly documented
      via internal headers. Additional documentation is available
      in separate ASCII text files called Required Reading files.
      For example, the S- and P- Kernel (SPK) Required Reading File,
      named SPK.REQ, describes use of the SPK kernel file readers
      and contains sample programs.

      The latest SPICE Toolkit for a variety of computer platforms such
      as PC, Mac, SUN, etc. is available at the NAIF Node of PDS
      electronically (via anonymous FTP and WWW servers). Refer to
      information in ``software/softinfo.txt'' for details regarding
      obtaining this software.


      Loading Kernel Files into a SPICE-based Application
      ===================================================

      The easiest way to make data from a collection of SPICE kernels
      available to a SPICE-based application is to list these kernels
      in a meta-kernel and load it into the program using the high
      level SPICE data loader routine FURNSH. This data set provides
      such meta-kernel(s) under the ``extras/mk'' directory. For more
      information about the New Horizons meta-kernel(s), see the file
      ``extras/mk/mkinfo.txt''.

This data set contains SPICE kernel files created during mission
      operations, and after mission data reconstruction and analysis.
      Some general information about this collection follows here,
      and additional metadata can be found within the files themselves.
      These metadata provide detailed information regarding
      the information source from which the data were derived, the
      type of processing applied to the source data, applicability
      of the data, etc. Metadata are located in the ``comment area''
      for binary kernel types (SPK, CK), accessible using either
      the COMMNT or SPACIT utility program found in the NAIF Toolkit.
      Metadata are located after ``\begintext'' markers within the
      text kernel types (PCK, IK, FK, LSK, SCLK), accessible by
      using any available text file display tool such as a word
      processor, text editor, or the unix ``more'' or ``cat''
      commands.

      In some cases data accuracy information does not exist because
      it could not be estimated even after mission completion.

      Where there are questions about data accuracy or ``confidence''
      not addressed herein the reader is invited to examine subsequent
      SPICE archive releases associated with this data set (if such
      exist), or to contact the New Horizons Science Operations Center.


      SPK Files
      =========

      The SP-Kernel files included in this dataset provide the trajectory
      of the New Horizons spacecraft and ephemeris data for the
      mission targets.

      In general, NH SPK files are accurate to 200 km 3-D 1 sigma with
      Inertial Velocity uncertainty of 3.3 mm/s 3-D 1 sigma during the Launch
      mission phase (Earth to Jupiter) and 10,000 km 3-D 1 sigma with Inertial
      Velocity uncertainty of 6.7 mm/s 3-D 1-sigma during the Pluto Cruise
      mission phase (Jupiter to Pluto/Charon).

      One of the most recent Orbital Determination SPKs has
      been provided with this latest release.  Note that the Project has
      moved on to JPL DE-433 (Developmental Ephemeris version 433), and will
      move on to later versions as needed; previous releases of this data set
      used DE-413 and DE-418.  While the user is cautioned when mixing the
      new and old kernels, all observations taken during the time covered
      by the new kernels are so far from any objects that the effect of
      mixing these kernels will almost always be small.  This should be
      considered a necessary inconvenience of archiving data from an active
      mission; doing so is akin to hitting a moving target.  At the end of
      the mission the project will deliver final trajectories, which will
      all use a consistent basis.

      Additional information about SPK files provided in this data set
      is available in the file ``data/spk/spkinfo.txt''.


      CK Files
      ========

      C-kernel files included in this dataset provide the orientation of
      the New Horizons spacecraft. These CK files were produced from
      engineering telemetry downlinked from the spacecraft.

      The spacecraft spent much of the mission to-date in hibernation
      mode and in a stable spinning attitude.  During Annual Checkout
      (ACO) activities, typically taking only a few weeks per year, the
      spacecraft drops down into 3-axis stabilized attitude.  Spinning
      mode can be detected in the C-Kernels by seeing an angular velocity
      of ~5RPM around the spacecraft Y axis.  The Spin/e-axis interval
      tables, derived from C-Kernles, are provided in the document/spinstate/
      subdirectory.

      Gaps exist in the CK coverage of New Horizons. During these gaps,
      many of which correspond to periods when the spacecraft was in
      hibernation, no attitude information is available. Use the CKBRIEF or
      FRMDIFF SPICE utility programs to see a CK coverage summary.

      Additional information about CK files provided in this data set
      is available in the file ``data/ck/ckinfo.txt''.


      PCK Files
      =========

      PCK files provide size, shape and orientation data for ``target''
      bodies such as planets, satellites, comets and asteroids. A
      description of these data items and reference to their source is
      provided inside the PCK file, which is a simple text file that
      can be viewed using any word processor, text editor or text
      display utility.

      Additional information about PCK files provided in this data set
      is available in the file ``data/pck/pckinfo.txt''.


      FK Files
      ========

      Frames kernel files provide specifications for how one reference
      frame is defined relative to another frame. The NH FK provided in
      this data set contains a complete set of frame definitions for
      the spacecraft and all its science instruments. Comments in the
      FK file provide the frame definitions, a description of the frame
      relationships, the source of and accuracy of the mounting alignment
      information, etc. The instrument frame definitions provided in the
      file incorporate the latest mounting alignment data available.

      Additional information about FK files provided in this data set
      is available in the file ``data/fk/fkinfo.txt''.


      IK Files
      ========

      Instrument kernel files provide specifications for the remote
      sensing and particles instrument parameters and -- where
      applicable -- field-of-view size, shape and orientation for the
      named instrument. Metadata describing these estimates are provided
      in each IK file included in this archive.

      Additional information about IK files provided in this data set
      is available in the file ``data/ik/ikinfo.txt''.


      SCLK Files
      ==========

      Spacecraft Clock kernel files provide a tabulation of data needed
      to convert time measurements between ephemeris time (ET) and
      spacecraft clock time (SCLK). Each newly made SCLK file fully
      replaces the previous SCLK file.

      There is ~2.3 second discontinuity at the boundary of the first (seeded)
      and second (the first actual) records in the SCLK file. Subsequent
      boundaries are aligned. The cause of the ~2.3 s discrepancy is unknown.

      Additional information about SCLK files provided in this data set
      is available in the file ``data/sclk/sclkinfo.txt''.


      LSK Files
      =========

      Leapseconds kernel files provide a tabulation of ``leapseconds''
      and some other terms used in converting time measurements between
      ephemeris time (ET) and Universal Time (UTC). ``Spacecraft Event
      Time'' (SCET) is the commonly used name for UTC events measured
      at the spacecraft.

      Metadata describing how the LSK data are obtained or computed is
      contained inside the LSK text file. The time conversion provided
      by SPICE LSK files is accurate to approximately 0.000030 seconds.

      Additional information about LSK files provided in this data set
      is available in the file ``data/lsk/lskinfo.txt''.

      DSK Files
      =========

      Digital Shape kernel (DSK) files provide target object shape data
      in a variety of digital shape representations, such as triangular
      plate models or digital elevation models. The DSK files included
      in this data set provide triangular plate shape models for Kuiper
      Belt Object (KBO) 2014 MU69 (Arrokoth) produced by the New Horizons
      science team. DSK files for the Pluto system are not currently
      included in the data set.

      More information about the DSK files is available in the file
      ``data/dsk/dskinfo.txt''.

      EK Files
      ========

      The New Horizons project did not produce any EK files; therefore,
      no EKs are included in this data set.