Data Set Overview
      =================
      This data set presents images of the nucleus of comet 1P/Halley
      obtained by the various contributing observers of the
      International Halley Watch (IHW) Near-Nucleus Studies Network
      (NNSN) over the period 16 October 1982 to 12 April 1989.
      Observers around the world contributed to this data set,
      which consists of 3523 well-documented FITS images.

      The data are broken down into directories by date.  The NNSN
      used a standard reporting format for keywords in the FITS
      header.  The images themselves are all either 2-byte or 4-byte
      integer data.  Calibrated and uncalibrated data appear in the
      same directory.  See the individual data labels (DESCRIPTION
      keyword) and the NNSN appendix for additional information,
      including comments on processing and FITS header keyword
      descriptions.

      This data set supercedes IHW-C-NNSN-3-EDR-HALLEY-V1.0 and includes
      the corrections for scan line corruption from
      IHW-C-NNSN-3-EDR-HALLEY-ADDENDA-V1.0.

      Modification History
      ====================
      Generation of the version 2.0 form of this data set consisted
      of the following:

        o  Concatenation of FITS headers and data segments to restore
           compliant FITS image files.  No modifications were made to
           either FITS headers or FITS data segments at this step.

        o  Generation of new PDS labels, incorporating as many keyword
           values and comments from the FITS file headers as possible.

        o  Sorting into monthly directories.

        o  Creation of a summary index file for all images.

        o  Application of the errata noted by Mikael Aronsson (JPL) as
           he compiled the IHW Printed Archive and Printed Archive
           Index.

        o  Correction (where possible) or notation directly in the labels
           of errata submitted by others since original publication.

        o  Correction of some minor FITS header syntax issues noted while
           working with the data files.

        o  All arrays and orientation metadata (including FITS headers)
           were examined and corrected as needed.  See
           orientation-time-scale-revs.asc for details.

        o  Pixel scale metadata (including FITS headers) were also
           updated, as needed.  See orientation-time-scale-revs.asc for
           details.

        o  Some image times were also updated.  See
           orientation-time-scale-revs.asc for details.

      Thanks to Nalin Samarasinha and Cassandra Lejoy for identifying some
      orientation and time issues.

      25 August 2006, A.C.Raugh
      31 October 2019, M.S.P.Kelley

Confidence Level Overview
      =========================
      A general data quality indicator was provided for each image in
      the FITS header, carried over into the PDS label in the keyword
      DATA_QUALITY_DESC.  The four values of this keyword are EXCELLENT,
      GOOD, FAIR and POOR.  Images rated POOR were included only when
      better data were not available for a particular date.

      Users should consult 'The Comet Halley Archive Summary Volume'
      (JPL D-400-450) for a discussion of the completeness and of the
      collection and overall quality considerations.  The NNSN appendix
      is included this data set's documentation.

      See the documentation directory for a summary of known data set
      issues.