DATA SET OVERVIEW
  =================

    The Cassini Ion and Neutral Mass Spectrometer (INMS) Packet data
    set contains all telemetry packets as received from the
    instrument. One standard product data type is defined for each
    INMS telemetry Packet. In each standard data product. one record
    is produced for each packet. Each item in the packet is converted
    from data numbers to dimensional values. The data set
    contains all science packets for the entire Cassini mission. The
    data set includes telemetry data from the instrument checkout
    periods, SOI and the entire Saturn tour.Each standard data product
    is organized as a spread sheet with one row for each packet. Each
    column in the spread sheet contains the contents of one item in
    the telemetry packet, converted from data number to dimensional
    quantities where appropriate.


  PARAMETERS
  ==========

    The INMS Packet data set includes five standard data product
    types, outlined in the table below. The first four data products
    contain the telemetry packets converted to dimensional quantities
    and are produced at a cadence of one record per telemetry
    packet. The contents of each standard data product type are
    described more fully below:

    Standard Data   Contents                    Data Rate
    Product Type

    INMS_SCI        Science(SCI)  Packets       Variable

    INMS_HKG        Housekeeping (HKG) Packets  68 s

    INMS_HMD        HKG Memory Dump Packets     68 s

    INMS_SMD        SCO Memory Dump Packets     Variable

    INMS_OTS        Operational Table Sets      Not Applicable


    INMS_SCI
    --------

      The Science Packet data product includes one record per
      instrument integration period.  The integration period, at full
      telemetry rate, is 31 ms with samples collected at a 34 ms
      cadence. When telemetry bandwidth is limited, measurements are
      accumulated by the instrument software prior to construction of
      the telemetry packet. In this case the integration period is
      equal to the number of measurements accumulated to form the
      telemetry packet times the basic 31 ms integration
      period. Parameters in the file include packet identification,
      instrument state and status, and 68 counter values for the low
      and high sensitivity counters.

    INMS_HKG
    --------

      The Housekeeping Packet Data product includes one record per
      housekeeping packet.  The housekeeping packets are produced at a
      68 second cadence.  Parameters in the file include packet
      identification, instrument state and status. Housekeeping
      packets are not produced when a housekeeping memory dump is in
      progress.

    INMS_HMD
    --------

      The Housekeeping Memory Dump product contains memory dump
      information and is produced only for those time periods during
      which a memory dump through the housekeeping telemetry was in
      progress.  Housekeeping data packets are produced on a 68 second
      cadence Parameters in the file include packet identification,
      instrument state and status, and 32 words of memory image.

    INMS_SMD
    --------

      The Science Memory Dump product contains memory dump information
      and is produced only for those time periods during which a
      memory dump through the science telemetry was in
      progress. Science memory dump packets are produced at a rate
      which depends on the data rate asigned to the INMS
      instrument. Parameters in the file include packet
      identification, instrument state and status, and 171 words of
      memory image.


  PROCESSING
  ==========

    The data in this data set is minimally processed. Instrument state
    information is converted from data numbers to dimensional
    quantities by applying calibration constants.


  COORDINATE SYSTEM
  =================

    Not Applicable

  SOFTWARE
  ========



  MEDIA FORMAT
  ============

    The data are archived on either CDROM or DVDROM media. The data
    files are stored in a comma-separated ASCII spreadsheet form that
    is described in the detached PDS label (Spreadsheet Object). The
    structure of the spreadsheet is specified in the format file
    included, by pointer, in the PDS label.

CONFIDENCE LEVEL OVERVIEW
  =========================

    This data set contains all of the telemetry packets produced by
    the Cassini INMS instrument for the intervals described in the
    labels of the individual data files.


  REVIEW
  ======

    The INMS Packet data set will be reviewed internally by the
    Cassini INMS team prior to release to the PDS. The data set will
    also undergo a PDS peer review prior to release.


  DATA COVERAGE AND QUALITY
  =========================

    PRIOR TO SOI
    ------------

      Prior to SOI the INMS instrument was evacuated and the aperture
      was closed by a cover installed prior to launch. The instrument
      was operated during in-flight check-outs (ICO) collecting
      baseline calibration data. During the approach science phase,
      INMS was operated nearly continuously to obtain operational
      experience and to validated data collection tables. Data is available
      for the following periods:

      ICO-1
      1999-005 1999-006 1999-009 1999-010 1999-021

      ICO-2
      none

      Approach
      2003-226 through 2003-230
      2003-315
      2003-321 through 2003-328
      2004-011 through 2004-018
      2004-058 through 2004-060
      2004-064 through 2004-071
      2004-092 through 2004-131
      2004-135 through 2004-163
      2004-171 through 2004-174

      The INMS cover was jettisoned immediately following SOI, permitting
      measurements of the ion and neutral constituents.


    POST SOI
    --------

      INMS science data collection began at SOI. From SOI onwards, the
      instrument was essentially in continuous operation.

      An issue with velocity compensation exists from launch through
      2005-058 which results in differences between the flight
      software computed quad lens bias voltages and ground computed
      values for the same velocity. This issue results in signal level
      changes when switching between velocity compensated scans and
      energy scans with ground computed quad lens voltages. The issue
      is resolved in data collected after TBS-DATE by correcting the
      ground computation of lens bias voltages.

      Prior to 2005-058 the flight software velocity compensation
      algorithm clipped only the lens voltage that reached its limit,
      allowing the other three voltages to be adjusted. This resulted
      in the voltages failing to maintain their proper relation-
      ships. This was corrected by insuring that once one
      voltage reached its limit, all four voltages were frozen.

      The spacecraft background command sequence was halted on 2004-185
      and it was resumed on 2004-194. During this period, housekeeping
      data was produced on all days but day 2004-191.

      During the period from 2005-007 through 2005-014, the instrument
      was shut down while the Probe mission occurred. No packet data
      was produced during this period.

      During the period from 2005-015 through 2005-021, only realtime
      housekeeping data was produced, no SCI packets were recorded
      on board while waiting for the Probe mission data to be validated.

      During S31 (from 2007-182), S32, S33, and S34 (to 2007-273) data gaps
      of more than one day occurred on days 255, 256, and 257 resulting in
      the PKT file being absent from the data for those days. These gaps were
      the result of spacecraft safing.

      During S48 (from 2009-091), S49, S50, S51 (to 2009-181) data gaps
      of more than one day occurred on day 124 resulting in
      the PKT file being absent from the data for those days. These gaps were
      the result of a Deep Space Network station breakdown.

      During S56 (from 2010-001), S57, S58 (to 2010-090) data gaps
      of more than one day occurred on days 003, 004, and 005 resulting in
      the PKT file being absent from the data for those days. These gaps were
      the result of the instrument being turned Off because of an SSPS
      Trip on the spacecraft.

      During S63 (from 2010-274), S64, S65 (to 2010-365) data gaps
      of more than one day occurred on days 307-318 resulting in
      the PKT file being absent from the data for those days. These gaps were
      the result of the instrument being turned Off because of a
      spacecraft safing event.

      During S75, data gaps of more than one day occurred on days
      2013-294 through 2013-302 resulting in the PKT file being absent from
      the data for those days.  These gaps were the result of the instrument
      being turned off during the Cassini Propellant Gauge Test.

      During S83 (from 2014-091) and S84 (to 2014-181) a data gap of more
      than one day occurred on day 128 resulting in the PKT file being absent
      from the data for that day. This gap was the result of telemetry gaps.

      During S92 (from 2016-001), the data gap on day 021 was a result of an
      end of mission downlink test which resulted in the PKT file being
      absent from the data for that day.

      During S101 (from 2017-191), the data gap on day 208, 209, and 231 were
      the result of putting the instrument to sleep for table loads for the
      final proximal orbits.   No data is available past 2017-258, as the
      mission ended by flying the Cassini spacecraft into Saturn.

  LIMITATIONS
  ===========

    During the period from launch through 2004-256, a flight software
    error caused data corruption when mass scans were accumulated to
    reduce data rates. These data are identified by a value of the
    COADD_CNT greater than 1.

    Prior to 2005-058 the flight software velocity compensation
    algorithm clipped only the lens voltage that reached its limit,
    allowing the other three voltages to be adjusted. This resulted in
    the voltages failing to maintain their proper relation- ships. This
    was corrected by insuring that once one voltage reached its limit,
    all four voltages were frozen.

   The Earth Received Time (TERTTIME) and the Processed Time (TPROCESSEDTIME)
   are reversed in the HKG data in version 5 files (and earlier versions).
   This has been corrected in version 6 files.