Data Set Overview
      =================
      This data set (VG1-J-PRA-3-RDR-LOWBAND-6SEC-V1.0) contains
      data acquired by the Voyager-1 Planetary Radio Astronomy (PRA)
      instrument during the Jupiter encounter. The bounding time
      interval set for most Voyager 1 Jupiter PDS data sets is the
      Voyager project defined 'far encounter' mission phase boundary
      (1979-02-28 to 1979-03-22). Since, however, the PRA instrument
      is able to observe planetary phenomenon at much larger ranges
      than other fields and particles experiments, this boundary is
      artificial with respect to PRA. Hence, PRA lowband data
      provided here cover the entire Jupiter Encounter Phase
      (1979-01-06 to 1979-04-13). Data from beyond the far encounter
      interval is contained in the cruise data archive which is
      available from the NSSDC.

      VG1-J-PRA-3-RDR-LOWBAND-6SEC-V1.0 contains data at the highest
      time resolution possible during normal operations. The normal
      mode of PRA operations during the planetary encounters was to
      sweep through the two radio receiver bands, high band (40.5 to
      1.5 MHz in 128 channels spaced 0.3072 MHz apart) and low band
      (1326.0 to 1.2 kHz in 70 channels spaced 19.2 kHz apart) in a
      period of 6 seconds. The receivers measured, on alternate
      samples, the left hand circular and right hand circular (radio
      definition) power.

      Measured Parameters
      ===================
      The data here are from the low frequency receiver band and are
      'packaged' into spacecraft major frame records. Each major
      frame is 48 seconds long or eight sweeps through the PRA
      receiver. The data are calibrated and are given in units of
      'millibels' which is 1000 times the log of the received power.
      Zero millbels corresponds to approximately 1.4 x 10^-21 W m^-2
      Hz^-1, however, this value is never seen in practice. The
      minimum values detected, which includes receiver internal and
      spacecraft generated noise, are about 2300 to 2400 millibels,
      or about 3.5 x 10^-19 W m^-2 Hz^-1; even higher values are seen
      at the very lowest frequencies.

      The data format is ASCII and consists of a time indicator
      followed by an array containing the eight low band sweeps. Time
      is spacecraft event time (SCET) which is basically universal
      time at the spacecraft. Specifically, time is in the form of
      YYMMDD and seconds into YYMMDD. Both are written as I6.
      Example: July 1, 1979 at 12 hours SCET would be 790701, 43200.
      The seconds correspond, to the nearest second, to the start of
      the sweep (which occurs in PRA high band). The first value in
      low band (1326.0 kHz) occurs some 3.9 seconds after this time
      and samples at successively lower frequencies are spaced 0.03
      seconds apart. Only one time is given for the entire major
      frame, thus the start of each sweep is the time given plus 6
      times the sweep number minus 1 (i.e., 0 through 7).

      The data array is dimensioned as 71 X 8 and written as I4
      format (i.e. 568I4). The '8' corresponds to the eight PRA
      sweeps. The lowest 68 of the 70 low band channels (1287.6
      to 1.2 kHz) are in positions 2-69.  Positions 70-71 should be
      ignored. Missing or bad data values are set to zero. In
      position 1 of each sweep is a status word where the 12 least
      significant bits have used, although not all 12 have meaning
      for PRA low band. Numbering those bits 0 for least significant
      to 11 for most significant, the bits that have meaning are as
      follows:
      bit
       0: 15 dB attenuator in use when equal to 1
       1: 30 dB attenuator in use when equal to 1
       2: 45 dB attenuator in use when equal to 1
       9,10 (together): polarization of first channel sampled (1326.0
                        kHz) according to the scheme:
                       value bit 10 =
                               0 1
              value bit 9 = 0  R L
                            1  L R

      Polarization at successively lower frequencies is opposite to
      the frequency above it, i.e. either a LRLR or an RLRL pattern.
      Successive 6-second sweeps start on the opposite polarization
      as the previous sweep as indicated in the status bits. Note
      that this polarization is the received polarization, not
      necessarily the emitted polarization. Correct interpretation of
      the received polarization depends on the antenna plane
      orientation relative to the radio source. A good description of
      this concept can be found in [LEBLANCETAL1987].

      Missing or bad data values are set to zero. If the status word
      is zero, any data in that receiver sweep should be discarded.

      Data Coverage
      =============
      Filename   Records               Start                 Stop
      -----------------------------------------------------------------------
      Volume ID: VGPR_1201
      PRA_I.TAB   35569   1979-01-06T00:00:34.000Z  1979-01-30T23:59:47.000Z
      PRA_II.TAB  39493   1979-01-31T00:00:35.000Z  1979-02-25T23:59:47.000Z
      PRA_III.TAB 41371   1979-02-26T00:00:35.000Z  1979-03-22T23:59:56.000Z
      PRA_IV.TAB  24587   1979-03-23T00:00:44.000Z  1979-04-13T23:59:08.000Z

Confidence Level Overview
      =========================

      The accuracy of calibration in the PRA low band is
      approximately 2 dB, except at frequencies below 100 kHz where
      it is somewhat worse. Interference from the Voyager power
      subsystem is a major problem to the PRA instrument, affecting
      many of the 70 low band channels. This interference manifests
      itself by abrupt changes in background levels. Some channels,
      notably 136 and 193 kHz, are almost always affected, whereas,
      others are only affected for short intervals. Usually, this
      interference is only a problem when the natural signals are
      weak.