Data Set Overview
      =================
      This data set represents data derived from low-resolution optical
      spectra of comet 9P/Tempel 1 obtained with one of two instruments
      using the 2.7m Harlan J. Smith Telescope of McDonald Observatory.
      These data are published in Cochran, et al. (2009) 'Placing the
      Deep Impact Mission into context: Two Decades of observations of
      9P/Tempel 1 from McDonald Observatory', Icarus 199, 119-129.
 
      In 1983, observations were obtained with the Intensified Dissector
      Scanner (IDS) spectrograph with a resolution of 11A.  This
      instrument had two entrance apertures of 4x4 arcsec located 52
      arcsec apart. The typical model of operation was to beam-switch
      between the two slits in order to observe object and sky or
      multiple positions on an extended object. Other positions within
      the coma could be sampled by moving the telescope.  A complete
      description of this instrument and the reduction procedures may
      be found in Cochran, et al., 1992, 'The McDonald Observatory
      Faint Comet Survey:  Gas Production in 17 Comets', Icarus 98,
      151-162.  These data were archived in the PDS as the data set
      EAR-C-MCDIDS-3-RDR-MCDNLD-V1.0.
 
      In 1989, 1994 and 2005 observations were obtained with the Large
      Cassegrain Spectrograph (LCS), a long slit CCD spectrograph used
      at a resolution of 7A.  The slit was 2 arcsec x 150 arcsec with
      pixels of 1.28 arcsec in the spatial direction.  Spectra from
      each pixel (or binned pixels) were handled separately in a manner
      similar to that described in Cochran, et al. (1992), cited above.
      With the LCS, the slit could be rotated to arbitrary position
      angles in order to probe different regions of the coma.  These
      data comprise the present data set.
 
      Integrated fluxes were calculated from sky and solar-continuum
      subtracted spectra.  These fluxes were converted to column
      densities using fluorescence factors listed in a separate table
      in the data set.
 
      The dataset includes the position of an observation along with the
      integrated fluxes and column densities for each night of observation
      for each molecule observed and at each position angle for the LCS
      data only.  The IDS data have already been archived in the PDS SBN
      as data set EAR-C-MCDIDS-3-RDR-MCDNLD-V1.0, 'MCDONALD OBSERVATORY
      FAINT COMET SPECTRO-PHOTOMETRIC SURVEY'.
 
      The data set contains a table which is the observation log for each
      instrument and a file documenting the reduction procedures.  The
      latter includes tables of g factos and bandpasses for the flux
      integration of each molecule and of the continuum region used.
 
      For each night of observations there are individual files for each
      molecule and each position angle.  Each of these files contains many
      lines of data representing the values at all observed spatial
      positions.
 
      The directory names indicate the molecule.  Within each molecule
      directory, the file names indicate the date of observation and the
      position angle of the slit:
 
        CN/
         |  20050512_090.TAB
         |      |     |
         |      |     |_______ Position angle of the slit - integer
         |      |_____________ Date as YYYYMMDD
         |____________________ Molecule (subdirectory name)
 
 
      Molecule may be OH, NH, CN, C3, CH, C2DEL1 or C2DEL0 where C2DEL1
      denotes the C2 delta v=1 band complex and C2DEL0 denotes the C2
      delta v=0 band complex.
 
      NOTE
      ====
      Due to a mix-up of file names, the production
      rates for 6 July 2005 quoted in tables 6 and 7 of
      Cochran, et al. (2009) are incorrect.  The corrected
      values are listed here.  They only differ slightly
      from the values quoted in the paper and thus do not
      change any of the conclusions.
 
 
        6 Jul 2005 Corrected Values
 
      Molecule     PA    Log Q     Npts   Bin
        OH         45    26.93:     32     2
                    0    26.85:     31     2
                   30    27.06:     18     2
 
        NH         45    25.24      56     2
                    0    25.22      52     2
                   30    25.17:     51     2
 
        CN         45    24.93     118     1
                    0    24.87     118     1
                   30    24.83     117     1
 
        C3         45    24.17     103     1
                    0    24.16     104     1
                   30    24.10      88     1
 
        CH         45    25.00:     48     2
                    0    25.07:     52     2
                   30    24.98:     50     2
 
      C2 del v=1   45    24.94     116     1
                    0    24.89     117     1
                   30    24.88     112     1
 
      C2 del v=0   45    24.90     116     1
                    0    24.89     116     1
                   30    24.88     116     1

Confidence Level Overview
        =========================
      For the LCS data there were a very large number of individual spatial
      positions observed and thus the uncertainties for each data table are
      best judged from the RMS of the scatter in the data.  When more than
      one position angle for the slit was used, the optocenter observations
      should yield the same column densities and differences represent
      another way of determining the uncertainties.
 
      Systematic uncertainties are caused by the choice of the fluorescence
      efficiency and the spectrophotometric calibration.