Data Set Overview
      =================
   
      This data set includes the complete set of SPICE data for Cassini
      in the form of SPICE kernels, which can be accessed using SPICE
      software available to read these files.

      The SPICE data contains geometric and other ancillary information
      needed to recover the full value of science instrument data.
      In particular SPICE kernels provide spacecraft and planetary
      ephemerides, instrument mounting alignments, spacecraft orientation
      and spacecraft sequences of events. Data needed for relevant time
      conversions is also included.

      This data set is contained on a single virtual volume, cosp_1000,
      including data from all mission phases and covering from launch,
      1997-10-15, 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 is accumulating with new data
      added approximately every three to six months. In addition, old
      data may be revised and added to the data set over time. Users are
      urged to be sure that they use the most recent data available by
      selecting files from the latest release, where appropriate.


      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 on the volumes comprising this data set.

      PCK kernels contain certain physical, dynamical and cartographic
      constants for target bodies, such as size and shape specifications,
      and orientation of the spin axis and prime meridian, that are meant to
      be used with applications that incorporate the SPICE Toolkit. PCK
      files are located under the ``data/pck'' directory on the volumes
      comprising 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 on the volumes comprising 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 on the volumes comprising this
      data set.

      EK (Events) kernels contain spacecraft and science instrument event
      related information. EK files are located under the ``data/ek''
      directory on the volumes comprising 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 on the volumes
      comprising 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 on the volumes comprising this data set.

      FK (Frame Definitions) kernels contain information required
      to define reference frames, sources of frame orientation data
      and inter-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 on the volumes comprising this data set.

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

            
      Kernel File Details
      ===================
      
      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. SPICELIB 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, HP, SGI, VAX, DEC Alpha, etc. is available
      at the NAIF Node of PDS electronically (via anonymous FTP and
      WWW servers). Refer to information in ``software/softinfo.txt''.
      Each version of the Toolkit is also archived at the NASA National
      Space Science Data Center.


      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 Cassini meta-kernel(s), see the file
      ``extras/mk/mkinfo.txt''.

This volume contains SPICE kernel files created during mission
      operations and after mission data reconstruction and analysis.
      Some general information about this collection follows here, but
      the prospective user is also referred to extensive descriptions
      about each file that are stored inside each kernel file. 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, EK), 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, or may be
      estimated 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 of this data set, or to contact the NAIF
      node of the Planetary Data System for possible further
      information.


      SPK Files 
      =========

      The following kinds of SPK files are provided in this archive: 

      -  SPK files containing reconstructed spacecraft trajectory and
         ephemeris information for the Solar system planets and major
         Saturnian satellites produced by the Cassini Navigation team
 
      -  SPK files containing ephemeris information for minor Saturnian
         satellites. produced by the Gravity Science team .

      -  SPK files containing ephemerides for the final comprehensive 
         CASSINI reconstruction. Produced by R.A. Jacobson. 

      For more information, see the file ``data/spk/spkinfo.txt''.

      This data set also includes two kinds of supplementary files with
      the information either derived from or describing the
      reconstructed SPK files. These files are not SPICE kernels; for
      this reason they are provided in subdirectories under the
      ``extras'' directory.
 
      The first kind of supplementary files is the orbit number files
      generated at the archive preparation time using the NAIF's ORBNUM
      utility program for the NAV SPK files covering the orbital phases
      of the mission. These files are provided in the ``extras/orbnum''
      directory. For more information about the orbit number files, see
      the file ``extras/orbnum/orbinfo.txt''.

      The second kind of supplementary files is the covariance table
      files containing the formal position uncertainties of Cassini's
      reconstructed ephemeris provided in the SPK files produced by the
      Cassini NAV Team. These files are provided in the
      ``extras/spkxtra/covtab'' directory. For more information about
      these files, see the file ``extras/spkxtra/covtab/covinfo.txt''.


      CK Files 
      =========

      The following kinds of CK files are provided in this archive:

      -  regular operational reconstructed spacecraft orientation CKs
         produced the Cassini Attitude Articulation Control Subsystem
         team (AACS). The absolute accuracy of the orientation provided
         in these CKs is no better than 40-microradians due to
         quantization granularity resulting from raw telemetry
         quaternions downlinked as a 16-bit signed integers.
 
      -  special high-fidelity reconstructed spacecraft orientation CKs
         produced by AACS, available only for a few short periods. The
         orientation in the CKs does not suffer from the quantization
         granularity issue.
 
      -  predicted spacecraft orientation CKs produced AACS, including
         latest regular versions delivered during operations and,
         superseding them, the final post-mission versions created in
         2018, intended to provide orientation for periods when
         reconstructed CK files have gaps in coverage
 
      -  predicted gap-filler spacecraft orientation CKs created by
         NAIF, intended to close small gaps between predicted CKs to
         achieve fully continuous orientation coverage for the whole
         mission
 
      -  image navigated (C-smithed) spacecraft orientation CKs
         produced by the Imaging Science Subsystem (ISS) team, covering
         only short intervals corresponding to the ISS image exposure
 
      -  CDA instrument orientation CKs created by NAIF using the
         instrument articulation data from the CDA team, providing
         orientation of the CDA instrument relative to the spacecraft
         bus.
 
      -  MIMI/LEMMS instrument orientation CKs created by the MIMI
         team, APL using the instrument articulation telemetry data,
         providing orientation of the MIMI/LEMMS instrument relative to
         the spacecraft bus.
 
      -  custom Saturn frames orientation CKs created by the MIMI team,
         APL based on custom Saturn rotation models, providing support
         data for the corresponding frames defined in the MIMI FK
         files.

      -  CAPS instrument orientation CKs created by NAIF/JPL using the 
         CAPS articulation angle data from CAPS ACT products in the CAPS
         PDS data sets and the nominal relationship between the CAPs 
         frames in the CASSINI FK.

      For more information, see the files ``data/ck/ckinfo.txt''.

      This data set also includes two kinds of supplementary files with
      the information either derived from or describing CK files. These
      files are not SPICE kernels; for this reason they are provided in
      subdirectories under the ``extras'' directory.

      The first kind of supplementary files is the comparison reports
      showing differences between predicted and reconstructed C-Kernels
      produced by AACS. These files are provided in the
      ``extras/ckxtra/cknav'' directory. For more information about
      them, see the file ``extras/ckxtra/cknav/navinfo.txt''.
 
      The second kind of supplementary files are related to the ISS
      image navigated CKs providing logs of angular differences between
      image navigated and reconstructed CKs, and graphic images that
      resulted from the image navigation process.  These files are
      provided in the `extras/ckxtra/ckiss'' directory. For more
      information about them, see the file
      ``extras/ckxtra/ckiss/issinfo.txt''.


      PCK Files 
      =========

      The following kinds of PCK files are provided in this archive:

      -  generic text PCK files based on the IAU reports, created by
         NAIF
 
      -  Cassini-specific text PCK files with data for planets and
         major satellites, created by the Cassini Instrument Operations
         team (IOT)
 
      -  Cassini-specific text PCK files containing data for the small
         satellites (rocks) of Saturn, created by IOT
 
      -  Cassini-specific binary PCK files containing orientation data
         for selected satellites, based on rotation models by M.S.
         Tiscareno, SETI.

      -  Enceladus-specific text PCK file containing rotation constants
         determined in 2023 by SSD/JPL when creating the SPC-based DSKs.

      A description of these data items and references to their source
      is provided inside each PCK file's comments. For more
      information, see the file ``data/pck/pckinfo.txt''.
 

      FK Files 
      ========

      The following kinds of FK files are provided in this archive: 

      -  main Cassini project FK files defining the spacecraft,
         structures, and instrument frames, created by NAIF
 
      -  rocks FK files defining body-fixed frames for the small
         satellites (rocks) of Saturn, created by IOT
 
      -  dynamic frames FK files defining dynamic frames used by
         various project science and engineering teams, created by NAIF
 
      -  MIMI FK files defining frames used by the MIMI team, created
         by the MIMI team, APL.

      A description of each reference frame is provided inside each FK
      file, which is a simple text file that can be viewed using any
      word processor, text editor or text display utility. For more
      information, see the file ``data/fk/fkinfo.txt''.
 

      IK Files 
      ========

      IK files providing specifications for field-of-view size, shape
      and orientation, and other of relevant instrument geometric
      parameters for each of the Cassini instruments, created by NAIF
      are included in this archive. Metadata describing these
      parameters are provided in each IK file comments. For more
      information, see the file ``data/ik/ikinfo.txt''.


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

      Spacecraft Clock kernel files providing a tabulation of data
      needed for converting time measurements between ephemeris time
      (ET) and spacecraft clock time (SCLK)for the Cassini on-board
      clock, created by the Spacecraft Team (SCT) are included in this
      archive. The report provided with the final post-mission
      reconstructed SCLK kernel created in 2018 stated that the fit
      limits were set to +/- 10 msec during periods when the s/c was
      using the CDS-A clock and to +/- 5 msec when the spacecraft was
      using the CDS-B clock. For more information, see the file
      ``data/sclk/sclkinfo.txt''.


      LSK Files 
      =========

      Generic Leapseconds kernel files providing a tabulation of
      ``leapseconds'' and some other terms used in converting time
      measurements between ephemeris time (ET) and Universal Time
      (UTC), created by NAIF are included in this archive. 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. For more
      information, see 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 Enceladus
      produced by the SSD, JPL. 
 
      More information about the DSK files is available in the file
      ``data/dsk/dskinfo.txt''.


      EK Files 
      =========

      The following kinds of Events kernel (EK) files are included in this
      archive: 

      -  Command Database EKs containing containing command and
         parameter descriptions, created by IOT
 
      -  Science Plan EKs containing detailed science requests and
         high-level observation plans, created by IOT
 
      -  Sequence EKs containing commands, ground events, subsystem
         status and notes taken from the integrated sequence Predicted
         Events Files, as well as ISS mechanical events (shutter and
         filter wheel movements) derived from the Multi-mission Image
         Processing Laboratory database used to process images, created
         by IOT.

      For a complete description of the EK files see the files
      ``document/ek/sis_ek_001_revc.pdf'', ``data/ek/ekinfo.txt'', and
      comments within the files.