Data Set Overview
    =================
    NASA's International Halley Watch (IHW) has created a Comet
    Halley Archive. The collection of data spans the full
    wavelength range as submitted by scientists to the IHW. The
    observations belong to one of the following Disciplines:
    Amateur, Astrometry, Infrared Studies, Large-Scale
    Phenomena, Meteor Studies, Near-Nucleus Studies, Photometry
    and Polarimetry, Radio Studies, and Spectroscopy and
    Spectrophotometry. The data collected by these nine
    disciplines were augmented by Spacecraft measurements. The
    data were submitted to IHW, but the evaluation and selection
    for the Archive has been the primary responsibility of the
    Discipline Specialist Teams for each network in cooperation
    with the Lead Center. The Spectroscopy and Spectrophotometry
    Network collected 352 files that represented the digitized
    spectra from plate material. In some cases, the non-Halley
    targets for the spectroscopic observations can be grouped
    according to 'laboratory' calibration, dark, bias,
    flatfield, sky, and photometric standards. In the first
    category, a large number of 'arcs' and 'lamps' were used as
    follows: HE-NE, TH-AR, NE-AR, CU-AR, CU-NE, Thorium,
    Tungsten, Quartz, and Rubidium. For the 'sky' observers used
    the twilight, moonlight, and blank sky. The most common
    'photometric' standards were stars, but observers also
    included other comets (Hartley-Goode), asteroids (Ceres),
    reflection nebulae (R8), and emission nebulae (NGC1982,
    NGC7000). A list of these stellar calibration targets
    follows: HD 140283, HD 184711, HD89688, HD102870, HD120086,
    HD13974, HD219188, HD 25680, HD 19445, HD18803, HD30455,
    HD26912, SAO 1280, HZ15, CD-22 7696, GD 190, GC5106, GC2188,
    GC2192, G19113213, G 99-37, L745-46A, Feige 15, Feige 56,
    Landolt 98, Landolt 92, Van Beuren, RHO ORION, CHI 1 ORION,
    29 PI LEO. For this data, no distinction about 'reduction'
    is distinguished for this process. The data cover the date
    range from 1985 October 17 through 1986 December 12.
 
 
  Processing Level Id            : 3
  Software Flag                  : N
 
 
  Parameters
  ==========
  Data Set Parameter Name        : PHOTOGRAPHIC DENSITY
  Data Set Parameter Unit        : PIXEL
 
 
    Description
    -----------
      A logarithmic measure of the transmissivity (or reflectivity
      in the case of a photographic print) of a photograph.
      Generally, density = -lg (transmissivity), but offsets of
      the zero point, e.g., to correct for the losses at surface
      reflections, and multiplicative scaling are sometimes used.
      The transmissivity can be measured as diffuse (including all
      the light scattered over 2 pi steradians) or as specular
      (including only the light transmitted straight through the
      photograph within a narrow range of angles from
      perpendicular).
 
      For the IHW LSPN data sets, specular density is used and the
      recorded value has been scaled by a multiplicative factor to
      increase the dynamic range.
 
 
    Source Instrument Parameters
    ============================
    Instrument Host ID              : SPEC
    Data Set Parameter Name         : PHOTOGRAPHIC DENSITY
    Instrument Parameter Name       : N/A
    Important Instrument Parameters : 0
 
 
  Measurement Information
  =======================
 
    Atmospheric Conditions
    ----------------------
      N/A
 
 
    Source
    ------
      N/A
 
 
    Calibration Standard
    --------------------
      N/A
 
 
    Wavelength Calibration
    ----------------------
      N/A
 
 
    Processing
    ==========
    N/A

Overview
    ========
    N/A