Data Set Overview
      =================
      This data set presents the infrared spectroscopy of Comet
      1P/Halley archived with the Infrared Studies Network (IRSN)
      of the International Halley Watch (IHW).  59 spectra were
      obtained over the period 1985-10-29 to 1986-05-24 at a
      number of observatories using various instrumental systems.
      The specific observatory and instrumentation used in any
      given observation are noted in the data product label.
 
      Note that while most files reported fluxes in W/cm^2/micron,
      some fluxes were reported in arbitrary units, and some files
      report flux ratio or flux density instead.  Users should
      read the labels carefully.
 
      In addition to the 59 spectra (7 of which are calibration
      observations), 25 scheduled observations are documented for
      data that were expected but never submitted to the archive.
 
      Modification History
      ====================
      The data labels and format have been modified extensively in
      version two of the archive.  The data were originally submitted
      as FITS image files with the spectra in the primary data segment
      as integers.  The binary data were converted to flat ASCII
      tables; any applicable BSCALE value was applied.  New PDS labels
      were generated using the information in the FITS headers.  All
      comments documenting keyword values have been captured in the
      new PDS labels, either as PDS elements or in descriptive text.
 
      The ASCII table files were edited to convert all wavelength
      columns to microns (i.e., any separate scaling factor noted in
      the FITS COMMENT records for the wavelength was applied).  When
      the scaling factor for the primary datum (usually flux) and the
      error bar were different, an additional scaling factor was
      applied to primary datum values so that measurements and
      errors were on the same scale.
 
      Significant digits were preserved in the data file editing
      process, and wherever possible an attempt has been made to
      avoid implying more significant digits than actually existed
      in the original data file.
 
      The null data reports have been preserved as FITS files and
      provided with new PDS labels.
 
      In addition, known errata were corrected, including both the
      errata noted by Mikael Aronsson at JPL as he prapared the
      IHW Printed Archive and Printed Archive Index documents (and
      included on the HAL_0023 volume), and the errata collected
      after publication at the PDS Small Bodies Node.
 
      General Notes
      =============
      Times
      -----
      The observation times were reported as day fractions with
      anywhere from one to five decimal places of precision.
      These have been converted to the ISO standard format
      (YYYY-MM-DDThh:mm:ss) to a corrsponding level of accuracy.
 
      System Codes
      ------------
      The IHW directives for the SYSTEM keyword in the original
      FITS files mandated a format of 'dooottii', where
      d = discipline, ooo = IAU observatory code, tt = country
      code, and ii = (optional) telescope/instrument number
      assigned by the Infrared Studies Network.  For observatories
      that did not have an IAU code, ooo = 500 and in most of
      these cases ii = 00.  Thus, all U.S. observatories without
      and IAU code will have SYSTEM = '25001600' in their IRSN
      contributions.
 
      23 August 2006, A.C.Raugh

Confidence Level Overview
      =========================
      Approximately one third of the submissions expected for this
      archive were never received.  These have been documented as
      far as possible in the form of FITS files containing only the
      primary header.
 
      Most of the individual observation files contain both the
      primary measurement and an error bar at each wavelength.
 
      Note that the the ASCII tables were generated from binary data
      files of fixed precision - specifically, 4-byte floating point
      numbers.  The observation values and error bars reported as
      floating-point values have therefore been printed as ASCII
      values with five significant regardless of the scale of the
      number.  Thus, it is possible that values in the same table may
      show different numbers of decimal places, depending on the range
      of magnitudes present.