Data Set Overview ================= McDonald Observatory 9P/Tempel 1 Spectral Observations 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 urn:nasa:pds:gbo-mcdonald:faint_comet_survey. 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 The IDS data have already been archived in the PDS SBN as data set urn:nasa:pds:gbo-mcdonald:faint_comet_survey, 'McDonald Observatory Faint Comet Spectro-Photometric Survey'.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.