Data Set Overview
    =================
      The OPE photopolarimeter was designed to measure
      the polarized components of the light in seven
      bandpasses or channels, ranging from the near
      ultraviolet to the near infrared.  Three channels
      (so- called blue, green and red) were devoted to
      the observation of the scattering of solar light by
      cometary dust grains, in emission-free countinuum
      bands.  Four other channels (so called OH, CN, CO+,
      C2) were devoted to the observation of light
      emitted by cometary gases.
 
      The imaging of a mosaic of interference filters
      (placed in front of the objective lens and
      organized into a mosaic to compensate for the
      chromatic effects) onto a microchannel plate
      allowed the spectral discrimination to be achieved.
      A polaroid analyzer, placed in front of each
      filter, except the CO+ one, allowed the
      polarization to be determined by the rotation of
      the analyzer with the spin of the spacecraft.
      During a spin period (of approximately 4 seconds),
      eight consecutive measurements of the polarized
      intensity, Ii, Ii+1, Ii+2, etc, (of approximately
      half a second each), were performed in the seven
      channels at eight so-called clock angles.
 
 
      Absolute calibration
 
 
      Due to the reduced amount of time available for
      calibrations after the flight detector was
      available, the absolute-radiance sensitivity of the
      instrument had been inferred by considering the
      individual spectral transmission of each optical
      component, the field of view of the instrument, the
      photocathode spectral sensitivity and the total
      responsivity of the microchannel plate
      photomultiplier (Giovane, 1991).  The results were
      the following:
 
 
Channel      Wavelength             Bandpass                Responsivity
                nm                  50% peak,nm     10-7 Wm-2sr-1mm-1ct-1
 
Blue            442                     5                       2.09
Green           576                     10                      0.88
Red		718			4			4.40
OH		310			6			16.81
CN		387			4			8.20
CO+		424			4			1.34
C2		514			4			3.75
 
 
      The on-board calibration tritium-phosphor source
      (mounted on the back of the baffle cover), which
      allowed the instrument to be tested during the
      pre-Halley-encounter cruise, was released with the
      baffle cover prior to Halley encounter.
 
      The data for Optical Probe Experiment was submitted
      by Andrew Weisenberger for the Frank Giovane at the
      Space Astronomy Laboratory, Univ of Florida.  The
      data are grouped by 'phases' into tabular form; the
      first four columns of the table are calibrated
      fluxes identified as P2, P3, P4, and CO+ (no
      contribution or only a very weak one, not separable
      from the underlying continuum exists for that gas
      channel).  No time is specifically given but rather
      the last column lists cometocentric distance
      ranging from 192041 to 947 km.  Each table
      corresponds to a specific phase.  Fluxes are
      collected at 500 ms intervals, one phase after
      another but are listed in each table at 4 s
      intervals (at every rotation of the spacecraft or
      about every 274 km along the spacecraft
      trajectory).
 
      Data for the gas are not given.  Three phases gave
      non usable data and are thus not provided here.  In
      all tables, the geometry relative to the comet is
      the same.  The distance to the nucleus can be used
      as a clock to identify the phase at which the
      observations were taken.

Confidence Level Overview
    =========================
      N/A