PDS_VERSION_ID          = PDS3
RECORD_TYPE             = STREAM
OBJECT                  = TEXT
  PUBLICATION_DATE        = 2006-10-03
  NOTE                    = "
    DATATIPS.TXT provides quick-start help for anyone wanting to write
    software to make use of the Voyager PWS full-resolution uncalibrated
    data on this volume."
END_OBJECT              = TEXT
END

========================================================================
DATA FILE OVERVIEW
========================================================================

The binary files containing the Voyager PWS full-resolution uncalibrated
data are found under directories named

  DATA/FULLv/Tyymm_mm

where v is 1 for Voyager 1 and 2 for Voyager 2, yy is the two-digit year,
and mm_mm indicates an inclusive range of four months.  The data files
are named

  Tyymmdd.DAT

where yymmdd represents the year, month, and day (SCET) of data
contained in the file.  Each file record is 48 bytes in length,
consisting of 24 low-byte-first (little-endian) 16-bit integer fields.
The detailed description of these fields is contained in the file

  VGRPWSEL.FMT

found in each data directory.  This file along with corresponding
Tyymmdd.LBL label files and the information in the CATALOG and DOCUMENT
directories provide full details.

========================================================================
DATA PROCESSING OVERVIEW
========================================================================

The uncalibrated integer data numbers contained in these files are
roughly proportional to the log of the voltage detected by the PWS
instrument in each of 16 frequency channels ranging from 10 Hz to 56.2
kHz, logarithmically spaced, four per decade:

                                   Voyager 1      Voyager 2
  Channel    Center Frequency      Bandwidth      Bandwidth
      1          10.0  Hz           2.99 Hz        2.16 Hz
      2          17.8  Hz           3.77 Hz        3.58 Hz
      3          31.1  Hz           7.50 Hz        4.50 Hz
      4          56.2  Hz          10.06 Hz       10.7  Hz
      5         100.   Hz          13.3  Hz       13.8  Hz
      6         178.   Hz          29.8  Hz       28.8  Hz
      7         311.   Hz          59.5  Hz       39.8  Hz
      8         562.   Hz         106    Hz       75.9  Hz
      9           1.00 kHz        133    Hz       75.9  Hz
     10           1.78 kHz        211    Hz      151.   Hz
     11           3.11 kHz        298    Hz      324.   Hz
     12           5.62 kHz        421    Hz      513.   Hz
     13          10.0  kHz        943    Hz      832.   Hz
     14          17.8  kHz       2110    Hz     1260    Hz
     15          31.1  kHz       4210    Hz     2400    Hz
     16          56.2  kHz       5950    Hz     3800    Hz

Of the 24 16-bit LSB integer items in each record, the most useful are:

  Item  Byte offset  Description
    1       0        SCET years past 1900 (2001 = 101)
    2       2        SCET hour of year plus 24
    3       4        SCET second of hour
    4       6        SCET millisecond of second
    9      16        data number from PWS channel 1
   10      18        data number from PWS channel 2
   . . .  . . .      . . .
   24      46        data number from PWS channel 16

An ASCII text file included in each data directory contains a
calibration table mapping each 8-bit instrument sample to a calibrated
voltage.  This file,

  VG1PWSCL.TAB, described in VGRPWSCL.FMT,

may be read and further manipulated to produce a look-up table for other
scientifically interesting units, such as:

  Electric field, V/m, calculated by dividing the values in VG1PWSCL.TAB
  by the effective electrical length of the PWS antenna, 7.07 meters;

  Spectral density, V**2/m**2/Hz, calculated by squaring the electric
  field and dividing by the noise bandwidth of the corresponding channel
  as given in the table above;

  Power flux, W/m**2/Hz, calculated by dividing the spectral density
  by the impedance of free space, 376.73 ohms.

Special caveats include:

  1.  Voyager 2 data for the upper 8 channels of the instrument must be
      adjusted to compensate for a degradation in sensitivity that
      occured early in the mission.

  2.  Only units proportional to power (or volts squared) are
      appropriate for averaging.

  3.  Some data numbers have been multiplied by -1 to indicate the
      presence of interference.

  4.  Data numbers for some telemetry modes are actually 10-bit sums
      of 4 instrument samples.

  5.  Zero data numbers indicate missing samples.

Typical ways of graphing these data for analysis include:

  1.  An amplitude vs. frequency spectrum taken either from a single
      data record or averaged over a larger period of time.

  2.  An amplitude vs. time plot of the time evolution of the signal
      detected in a single frequency channel.

  3.  Combined amplitude vs. time plots from several or all channels,
      resulting in a representation of the time evolution of the
      spectrum across a range of frequencies.  This is often presented
      as a "stacked histogram" or sometimes as a "spectrogram" with
      amplitude represented as color or shades of gray.

See the example code in EXTRAS/SOFTWARE/C for details on how to extract
calibrated values from these data.

The application in EXTRAS/SOFTWARE/JAVA provides all of the analysis
capabilities routinely used by the PWS team.

========================================================================