PDS_VERSION_ID                   = PDS3
LABEL_REVISION_NOTE              = "
             2012-08-30, D. Kazden, updated to meet PDS 3.8 standards;
             2020-02-11, D. Kazden, updated cITATION_DESC;"

  OBJECT                         = DATA_SET
  DATA_SET_ID                    = "PVO-V-OETP-5-IONOPAUSELOCATION-V1.0"

  OBJECT                         = DATA_SET_INFORMATION
    DATA_SET_NAME                  = "PVO VENUS ELECT TEMP PROBE DERVD
                                      IONOPAUSE LOCATION VER 1.0"
    DATA_SET_COLLECTION_MEMBER_FLG = N
    START_TIME                     = 1978-12-05T15:07:34.817
    STOP_TIME                      = 1992-10-07T19:46:27.000
    DATA_OBJECT_TYPE               = TABLE
    ARCHIVE_STATUS = ARCHIVED 
    DATA_SET_RELEASE_DATE          = 1993-10-01
    PRODUCER_FULL_NAME             = "DR. ROBERT F. THEIS"
    DETAILED_CATALOG_FLAG          = N
    ABSTRACT_DESC                  = "The Ionopause File. This file gives
    the orbit-by-orbit times and locations of the ionopause crossings, which
    are evident as sharp gradients in Ne at the top of the ionosphere.
    (These crossings always occur within 30 minutes of periapsis, so they
    may be seen in the High Resolution Ne files)."
    DATA_SET_TERSE_DESC            = "PVO VENUS ELECT TEMP PROBE DERVD
                                            IONOPAUSE LOCATION VER 1.0"
    CITATION_DESC       = "Theis, R. F., PVO-V-OETP-5-IONOPAUSELOCATION-V1.0,
                 PVO VENUS ELECT TEMP PROBE DERVD IONOPAUSE LOCATION VER 1.0,
                           NASA Planetary Data System, 1993."

    DATA_SET_DESC                  = "
The Ionopause File.  This file gives the orbit-by-orbit times and
locations of the ionopause crossings, which are evident as sharp gradients
in Ne at the top of the ionosphere. (These crossings always occur within 30
minutes of periapsis, so they may be seen in the High Resolution Ne files).

The ionopause and bow shock crossing times and locations are easily
identified in the high resolution Ne measurements (Theis et al., 1980).
These files contain the UT, altitude, latitude, SZA and local time of each
crossing.

On the dayside, the ionopause is taken (somewhat arbitrarily) at the level
in the steep gradient of the ionopause where Ne = 1x102 cm-3.  On the
nightside, the ionopause is selected at somewhat lower densities because
the absence of spacecraft photoelectrons lowers the Ne measurement
threshold.  In both cases, the intent is to identify the ionopause as the
point where the first rise of Ne above the background density occurs.  Of
course, the ionopause itself is not a point but is the extend region in which
the ionopause density gradient occurs."

    CONFIDENCE_LEVEL_NOTE          = "
The ionopause location is selected at that point in the steep gradient of the
ionopause where Ne crosses through the level of 1x102 cm-3.  When the
spacecraft is in darkness, the pe background is absent and the ionospheric
Ne is also much lower, so the ionopause is identified as the first rise in Ne
above whatever background is present.  The ionopause is identified by a
human operator who views each high resolution Ne pass plot on an
interactive computer terminal.  He selects the ionopause somewhat
subjectively as the time of the first rise above the background Ne, which
may consist of magnetosheath plasma or photoelectrons.  The 40 minute
pass plots used for this purpose provide only a 5-10 second accuracy in
the crossing times.  When irregularities or waviness in the ionopause
produce several ionopause crossings, the outer most crossing is the only
one identified."

  END_OBJECT                     = DATA_SET_INFORMATION

  OBJECT                           = DATA_SET_MISSION
    MISSION_NAME                   = "PIONEER VENUS"
  END_OBJECT                       = DATA_SET_MISSION

  OBJECT                         = DATA_SET_TARGET
    TARGET_NAME                    = VENUS
  END_OBJECT                     = DATA_SET_TARGET

  OBJECT                         = DATA_SET_HOST
    INSTRUMENT_HOST_ID             = PVO
    INSTRUMENT_ID                  = ONMS
  END_OBJECT                     = DATA_SET_HOST

  OBJECT                         = DATA_SET_REFERENCE_INFORMATION
    REFERENCE_KEY_ID             = "THEISETAL1980"
  END_OBJECT                     = DATA_SET_REFERENCE_INFORMATION

  END_OBJECT                     = DATA_SET
  END