Data Set Overview
  =================
      The Cassini Magnetospheric Imaging Instrument(MIMI) Charge Energy Mass
      Spectrometer (CHEMS) contains a deflection system and an overall field
      of view of 159 x 4 deg. that is comprised of three distinct energetic
      particle telescopes each having a field of view of 53 deg. x 4 deg.
      All telescopes share the same deflection mechanism, but each has its
      own start and stop microchannel plate (MCP) and its own solid-state
      detector (SSD). Much of the data returned by CHEMS is separated by
      telescope. The deflection plate power supply (DPPS) has 32 different
      voltages that can be applied across the deflection plates. For any
      single DPPS step, the electrostatic analyzer only transmits incoming
      ions within a narrow range of energy per charge (a 3% pass band).

      The CHEMS calibrated data set includes the Pulse Height Analysis (PHA)
      data collected during the Saturn tour. CHEMS PHA provides a list of
      individually detected particles, with specific detection parameters
      for each event, including TOF, energy deposited in the SSD, and
      telescope number. Telemetry data volume constraints do not allow all
      particle events detected by CHEMS to be sent in the MIMI data stream,
      so the PHA data need to be carefully normalized, and the procedures
      for doing this are described in the section on CHEMS in the MIMI User
      Guide [VANDEGRIFFETAL2012].

      The energy per charge data for six ion species (H+, He+, H2+, He++,
      O++, W+)  are presented in two forms. One form is a set of tables
      which are of variable length and use a comma to separate various
      fields, and the other is a PDF file containing the energy per charge
      spectrograms and are based on CHEMS PHA data.  (The W+ water ion group
      includes O+, OH+, H20+ and H30+)

      The original data has been decommutated and decoded by software at
      the Applied Physics Laboratory (APL) and further processed by software
      at the University of Maryland.  The data is provided in an calibrated
      form in conjunction with a PDS MIMI calibration volume COMIMI_0000
      which provides specific algorithms for the derivation of calibrated
      data.

      This data set should be among the first used by a user of any of the
      MIMI CHEMS archive as it will lead one to information required to
      search for more detailed or highly specialized features in the
      original data.

  Parameters
  ==========
      This data set comprises energy per charge intensities for six ion
      species (H+, He+, H2+, He++, O++, W+) for each telescope and the
      sum of all the telescopes of the CHEMS detector. (The W+ water ion
      group includes O+, OH+, H20+ and H30+). The data consists of 60 minute
      averages and cover 20 days per file. Each file includes the
      intensities for each of the 32 energy per charge steps.

      The product ID's consist of a prefix followed by a date range.
      The prfixes are:
    CPHAFLX0_T1_HP    The energy per charge data for H+ for telescope 1
    CPHAFLX0_T2_HP    The energy per charge data for H+ for telescope 2
    CPHAFLX0_T3_HP    The energy per charge data for H+ for telescope 3
    CPHAFLX0_TA_HP    The energy per charge data for H+ for all telescopes
    CPHAFLX0_T1_H2P   The energy per charge data for H2+ for telescope 1
    CPHAFLX0_T2_H2P   The energy per charge data for H2+ for telescope 2
    CPHAFLX0_T3_H2P   The energy per charge data for H2+ for telescope 3
    CPHAFLX0_TA_H2P   The energy per charge data for H2+ for all telescopes
    CPHAFLX0_T1_HEPP  The energy per charge data for He++ for telescope 1
    CPHAFLX0_T2_HEPP  The energy per charge data for He++ for telescope 2
    CPHAFLX0_T3_HEPP  The energy per charge data for He++ for telescope 3
    CPHAFLX0_TA_HEPP  The energy per charge data for He++ for all telescopes
    CPHAFLX0_T1_HEP   The energy per charge data for He+ for telescope 1
    CPHAFLX0_T2_HEP   The energy per charge data for He+ for telescope 2
    CPHAFLX0_T3_HEP   The energy per charge data for He+ for telescope 3
    CPHAFLX0_TA_HEP   The energy per charge data for He+ for all telescopes
    CPHAFLX0_T1_OPP   The energy per charge data for O++ for telescope 1
    CPHAFLX0_T2_OPP   The energy per charge data for O++ for telescope 2
    CPHAFLX0_T3_OPP   The energy per charge data for O++ for telescope 3
    CPHAFLX0_TA_OPP   The energy per charge data for O++ for all telescopes
    CPHAFLX0_T1_WP    The energy per charge data for W+ for telescope 1
    CPHAFLX0_T2_WP    The energy per charge data for W+ for telescope 2
    CPHAFLX0_T3_WP    The energy per charge data for W+ for telescope 3
    CPHAFLX0_TA_WP    The energy per charge data for W+ for all telescopes

      The standard data product ID's are gropuped by species and are:
    CHEMS_PHAFLUXAV_HP
    CHEMS_PHAFLUXAV_H2P
    CHEMS_PHAFLUXAV_HEPP
    CHEMS_PHAFLUXAV_HEP
    CHEMS_PHAFLUXAV_OPP
    CHEMS_PHAFLUXAV_WP
      Each of these logically incorporates four types of products -- one for
      each of the three telescopes and one for all telescopes.

      In addition, this data set includes energy per charge spectrograms for
      the same six species. Each PDF includes the spectrograms for each of
      the three telescopes and their sum.

      The standard data product ID's are:
    MIMI_CHEMS_SPGM_HP    The energy per charge spectrograms for H+
    MIMI_CHEMS_SPGM_H2P   The energy per charge spectrograms for H2+
    MIMI_CHEMS_SPGM_HEPP  The energy per charge spectrograms for He++
    MIMI_CHEMS_SPGM_HEP   The energy per charge spectrograms for He+
    MIMI_CHEMS_SPGM_OPP   The energy per charge spectrograms for O++
    MIMI_CHEMS_SPGM_WP    The energy per charge spectrograms for W+.



  Processing
  ==========
      Data in this data set were processed by the use of a number of
      software programs which calibrate, perform the 1 hour averages on the
      data, and create the spectrograms.

      In the original CHEMS data,  accumulation interval for basic and
      species rate counters is one DPPS step, which lasts for one subsector,
      where 16 subsectors make a sector, and 16 sectors make one spin.

      When the spacecraft is in staring mode then the MIMI DPU automatically
      creates a virtual spin that divides the time collection periods into 16
      sectors, 16 subsectors, and 16 microsectors and maintains a simple
      organizational structure for characterizing the collection of the time
      into time segments. When the spacecraft is spinning at a minimally
      defined spin rate (adopted by the MIMI DPU) then the MIMI data is
      automatically segregated into 16 sectors, 16 subsectors, and 16
      microsectors. Note that for CHEMS, there is a 150 millisecond dead time
      per DPPS step, and this must be subtracted from the subsector duration.

      Converting a species count rate in units of counts/sec into a
      differential intensity in units of counts/(sec*ster*cm2*keV) requires
      knowledge of the geometry factor of the instrument, the energy width
      of the channel, the detection efficiency for ions of that species, and
      the energy width of the channel expressed as an energy per charge. The
      procedures for calibrating CHEMS data are described in the section on
      CHEMS in the MIMI User Guide [VANDEGRIFFETAL2012].

  Data
  ====
      The MIMI CHEMS calibrated data set includes the 24 ASCII CSV tables
      (each associated with a Standard Product ID of CHEMS energy per charge
      data as a function of time collected from the MIMI CHEMS Detectors and
      collated into data sets. Each table contains variable length records
      for which the fields are comma delimited.

   CHEMS Energy Per Charge ASCII data
   ----------------------------------
      Fields include:
      Start and Stop minutes of hour long average
      Year, and midpoint of the hour-long average interval expressed as a
      fractional day of year.
      Radial_distance which is the position of Cassini at midpoint of the
      interval in Saturn radii
      Latitude of Cassini at midpoint of measurement in Saturn equatorial
      frame
      Local_time of Cassini at the midpoint of the measurement given in
      hours and in the Saturn equitorial frame.
      Particle intensity and the uncertainty in particle intensity for
      each of the 32 energy bands. Units are counts/sec/ster/cm^2/keV.

      This data set comprises energy per charge intensities in separate
      files for six ion species (H+, He+, H2+, He++, O++, W+) and for each
      telescope and the sum of all the telescopes of the CHEMS detector. The
      data consists of 60 minute averages and cover 20 days per file. Each
      file includes the intensities for each of the 32 energy per charge
      steps.

   CHEMS Energy Per Charge Spectrograms
   ------------------------------------
      This data set comprises six ion species plots in PDF files. There are
      4 horizontal panels in the plot. The top panel contains
      the average intensity from all three CHEMS telescopes combined (full
      4 degrees x 159 degrees FOV).  Each panel below is for an
      individual telescope (4 degrees x 53 degrees FOV) (1, 2, and 3
      respectively).

      Pixels are 15 percent in
      energy per charge by 60 minutes and are based on
      CHEMS PHA data.  The bottom axis is time covering a 20 day
      interval.  The y-axis is energy per charge (keV/e).  The
      color represents the differential intensity for this species, and
      the units are particles per (cm^2 sec sr keV/e).  No background has
      been subtracted.



  Ancillary Data
  ==============


  Coordinate System
  =================
      The data in this data set are measurements of counts/sec/ster/cm^2/keV
      based upon the orientation of the CHEMS instrument (CHEMS Center look
      direction). Particle flux effects are then determined by transforming
      from a spacecraft centered coordinate system, properly rotated to
      account for the appropriate CHEMS telescope direction, into whatever
      external coordinate (reference system) is most appropriate.


  Software
  ========
      There is access on the MIMI web site, to an analysis package currently
      being used by the MIMI team to browse, plot and analyze MIMI data that
      reads data directly from the PDS and makes available to anyone the
      same analysis and visualization capabilities currently used by the
      MIMI team. The main benifit of the tools is that they provide an
      intuitive way to browse and analyze the data without having to worry
      about calibration details or file access and file reading details.

  Media/Format
  ============
      These data are supplied to the Planetary Data System via electronic
      means and are then broken into segments based upon the media currently
      prescribed by PDS.

Confidence Level Overview
  =========================
      This data set contains all calibrated data for the CHEMS Detector as
      part of the Cassini MIMI instrument for the interval described above.
      Every effort has been made to ensure that all data returned to APL
      from the spacecraft is included and that the calibrated browse data
      products are accurate.

      As of this writing there are no known issues associated with the CHEMS
      detector that would limit the usability or reliability of the data.

  Review
  ======
      The MIMI CHEMS data will be reviewed internally by the Cassini MIMI
      team prior to release to the PDS. The data set will also be peer
      reviewed by the PDS.


  Data Coverage and Quality
  =========================
      All data in the stated interval are included, to the best of our
      knowledge and attempts to determine completeness.

   Large Data Gaps:
   1.  Post SOI                  2004-187 - 2004-193 - Spacecraft Safing
                                              shut off
   2. Tour                       2005-006 - 2005-015 -
   3. Tour                       2007-254 - 2007-258 - Spacecraft Safing
                                              shut off
   3. Tour                       2007-279 - 2007-291 - Spacecraft Flight
                                              S/W testing shut off
   3. Extended Mission           2009-071 - 2009-076 - Spacecraft Thruster
                                              branch swap, deactivated S48
                                              background sequence.
   3. Extended-Extended Mission  2010-306 - 2010-319 - Spacecraft Safing
                                              shut off
   3. Extended-Extended Mission  2012-293 - 2012-303 - Spacecraft Propellant
                                              Gauging Test shut off.

      On those days for which the instrument did not collect data either due
      to the instrument being off or due to communication issues, the data
      set will not contain any files.


  Limitations
  ===========
      As noted above there are no know issues associated with the data from
      the INCA detector as of the writing of this catalog.