McDonald Observatory Spectroscopy of 9P/Tempel 1 from 1989-2005

We report on low-spectral resolution observations of comet 9P/Tempel 1 from 1983, 1989, 1994 and 2005 using the 2.7m Harlan J. Smith telescope of McDonald Observatory. This comet was the target of NASA's Deep Impact mission and our observations allowed us to characterize the comet prior to the impact. In the published paper, we showed that the comet decreased in gas production from 1983 to 2005, with the decrease being different factors for different species. OH decreased by a factor 2.7, NH by 1.7, CN by 1.6, C3 by 1.8, CH by 1.4 and C2 by 1.3. Despite the decrease in overall gas production and these slightly different decrease factors, we found that the ratios of the gas production rates of OH, NH, C3, CH and C2 that of CN were constant over all of the apparitions. We saw no change in the production rate ratios after the impact. We found that the peak gas production occurred about two months prior to perihelion. This data set represents the integrated fluxes and column densities, mentioned 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., which were used to derive the production rates in that paper.