Data Set Overview
      =================
      This data set contains the results for the Implanted Ion Sensor (IIS)
      of the Johnstone Particle Analyser (JPA) instrument flown aboard the
      GIOTTO spacecraft during its extended mission to fly by comet
      P/Grigg-Skjellerup.  The IIS instrument produced data in three modes
      during the encountered, labelled as 'D4D', 'STC' and 'TOF'.  The
      files in this data set present the results obtained in those modes
      in the form of flat ASCII files.
 
      Parameters
      ==========
      In each mode, the data recorded are a distribution of counts over an
      integration period of 32 spins (Nominal spin rate is 4 seconds per
      spin). The three modes are:
 
        D4D    Four-dimensional (full) resolution mode.  Counts are binned
               by polar angle, azimuthal angle, energy level and mass group.
 
        TOF    Time-of-Flight mode.  All angular bins are combined; data are
               binned by energy level and time of flight.
 
        STC    Start vs Start-Stop mode.  In this mode, the number of impacts
               triggering a START pulse, and the number triggering both a
               START and STOP pulse (i.e., real events) are tabulated.
 
      Note that since the processing program used the same output matrix for
      all modes, dimension labels are sometimes misleading.  Consult the
      definitions in the PDS labels for clarification.
 
      Processing
      ==========
      These text files were produced by running the processing softare
      designed for this purpose at Mullard Space Science Laboratory,
      University College, London.  No further data processing was performed
      at the Small Bodies Node, apart from preparing the PDS labels.
 
      The data were processed once, the parameters adjusted, and the
      processing repeated.  During the download of this second pass, two
      files were lost: t1922205.txt and s1922205.txt.  These files were
      recovered from the first pass, with the loss of one data record at
      the beginning of each file. The STC files were reformatted to a more
      readable format from that of the second-pass output; and all files
      had carriage-control characters added to end record.
 
      Data
      ====
      These data have been corrected for know telemetry glitches and hardware
      failures, but are otherwise unprocessed.  They were used to generate
      the JPA part of the results listed in the JPAMG data set, which merges
      the analyzed results of these data with results from the magnetometer
      experiment.  The files are designed for visual inspection, rather than
      for input to another program.
 
      Media/Format
      ============
      The data set is available as part of the GEM CDROM collection,
      published by the PDS Small Bodies Node.

Confidence Level Overview
      =========================
      Note that these data were accepted 'as is' from the JPA team for the
      purpose of completing the deep archive.  They have undergone the PDS
      internal review process, but have not been reviewed externally.
 
      For more information about the reliability of the experiment itself,
      see the published documentation.