Data Set Overview
      =================
      This data set presents polarimetric observations of comet
      1P/Halley reported to the Photometry and Polarimetry Network
      (PPN) of the International Halley Watch (IHW) as normalized
      Stokes parameters.  All data were contributed by a single
      observer, A. Dollfus, working at the European Southern
      Observatory.  This revised version of the data set includes
      updated documentation and data formats.
 
      Modification History
      ====================
      The first versin of this data set contained 9 sets of
      individual observation files.  Each file set contained the
      results from a single night of observing.  Each file set
      consisted of a PDS label, a FITS table header and a
      (detached) FITS data segment.
 
      PDS personnel made the following changes to create version 2:
 
        o PDS labels were completely rewritten.  All comments,
          history and significant keywords from the FITS headers
          were either included as PDS keywords or documented in
          the DESCRIPTION sectino of each label.  The FITS
          headers were then discarded.
 
        o Observing times were given as day fractions with either
          two or three significant digits.  These were converted
          to ISO standard time format (yyyy-mm-ddThh:mm).  Fractions
          with three significant digits were converted to the nearest
          minute.  Those with two significant digits were converted
          to the nearest quarter hour.
 
        o The filter name and integration time fields, which were
          blank in all the original tables, were omitted from the
          reformatted data tables.
 
        o The filter parameters (center wavelength and FWHM), which
          were constant, were removed from the data tables and noted
          as keywords CENTER_FILTER_WAVELENGTH and BANDWIDTH in the
          PDS label.
 
          NOTE: The documentation for Version 1.0 of these data
                stated that no filter was used for these observations.
                The reason for the discrepancy is not clear.
 
        o The 'all.tab' file was created by adding the observatory,
          telescope, observer and file name to the records from
          each individual table file and concatenating the results
          into a single table.  This file was then sorted on the
          time field at the beginning of each record.
 
      29 June 2006, A.C.Raugh

Confidence Level Overview
      =========================
      1-sigma errors are reported for each of the Stokes parameters
      reported in the data records.