Data Set Overview
    =================
      The following describes the nature of instrument operation
      during the various periods for which IES data are available in
      this submission.  In all cases the data are electron and ion  counts as
      function of energy, azimuth (direction in the instrument symmetry plane)
      and elevation (angle above or below the symmetry plane).

      IES measured solar wind plasma continuously throughout this phase except
      for an occasional brief period if the S/C pointing was not optimal.
      Frequently low energy (<50 eV) ions were observed. These ions are
      believed to have been produced locally by photoionization and attracted
      to the S/C when charged negatively by an electron cloud. In addition,
      higher energy (~keV) pickup ions were observed from time to time.


    Processing
    ==========
      All Rosetta Plasma Consortium (RPC) data packets are transmitted
      together during downlinks with Rosetta. RPC data are retrieved
      from the Data Distribution System (DDS) at European Space
      Operations Centre (ESOC) to a central RPC data server at
      Imperial College London. Data for IES is copied from the RPC
      central data server by IESGS at Southwest Research Institute.

      The pipeline processing software is the IES Ground System
      (IESGS). IESGS extracts IES CCSDS packets from the RPC
      collective data files stored on the RPC central data server at
      Imperial College. These packets are used to build ion and
      electron data products. The data products are grouped by date
      and written out to PDS compliant archive data files. One data
      file is created for each day. IESGS also generates the labels
      for the archive data files. IES science products, archive and
      label files, and limited spectrograms are available to team
      scientists on the IESGS website.

    Coordinate System
    =================
      In order to determine IES pointing, attitude data for the
      Rosetta spacecraft is obtained through SPICE kernels and
      converted from the J2000 coordinate system to the HGRTN
      coordinate system.  HGRTN is the heliocentric RTN system such
      that the sun-spacecraft vector defines the positive x-axis and
      the positive y-axis is the cross-product of the heliographic
      polar axis and the HGRTN positive x-axis. J2000 is the inertial
      frame defined by the intersection of the Earth mean equator and
      the ecliptic plane at the J2000 epoch of January 1, 2000 at
      noon.

      The pointing for each bin of IES is thereafter determined by
      multiplying the converted spacecraft attitude matrix in HGRTN
      by the vector representation of each particle measurement bin.
      The resulting vectors represent the flow of particles through
      the respective particle measurement bins in HGRTN coordinates.

      SUB_SPACECRAFT_LATITUDE, SUB_SPACECRAFT_LONGITUDE are given in
      the Cheops reference frame. These parameters are computed at
      time t=START_TIME. Distances are given in km, angles in
      degrees.

    Updates for Version 2.0
    =======================
       This version implements the recommendations from the 2016 scientific
       peer review. Most relevant changes include the addition of the cycle
       duration field in the data products and a machine readable file in
       PDS format with the modes and their associated parameters.

Confidence Level Overview
    =========================
      This dataset is used by the IES science team after processing.
      This is done to ensure that the archived data contains good,
      valid products.

      Caveat about using IES Level 3 Differential Energy Flux data: The
      background subtraction technique used in the production of the Level 3
      Differential Energy Flux data does not work well for certain modes and as
      a result, the flux values may be slightly different from nominal. Please
      contact the IES team before using the data. Once the background
      subtraction issue is resolved, the IES team will deliver updated data.

    Review
    ======
      This archival data set was examined by the IES science team
      prior to submission to the NASA Planetary Data System (PDS) and ESA
      Plantetary Science Archive (PSA). It was reviewed by PDS, PSA, and the
      Rosetta data archive working group.
      The current set was peer reviewed scientifically in 2016 by external
      experts and the recommendations and fixes have been implemented.

    Limitations
    ===========
      None.