Data Set Overview ================= Spectral observations of Comet 19P/Borrelly This data set includes the raw column densities of several gas species observed in the spectra of comet Borrelly, as a function of position in the coma. All measurements were made with the 2.7-m Harlan J Smith Telescope at McDonald Observatory. During the 1981 and 1987-1988 apparitions, the data were obtained with the Intensified Dissector Scanner (IDS), and during the 1994 apparition, the data were obtained with the Large Cassegrain Spectrograph (LCS). The IDS and LCS tables give up to 4100 measurements of the column densities of different species at various positions in the coma. The species measured from the IDS data are C2 (two bands), CN, C3, CH and NH2. The species measured from the LCS data are C2 (two bands) OH, NH, CN, C3 and CH. The raw column density measurements as a function of position are presented here so that researchers can apply their own models to the data. The manuscript describing the data set in detail can be found in Cochran, A.L. and E.S. Barker (1999) ''McDonald Observatory Spectral Observations of Comet 19P/Borrelly'' Icarus 141, 307-315. [COCHRAN&BARKER1999] Table IV from that paper lists the production rates and Afrho values derived from the column densities. The information in this table was not submitted for inclusion in this data set. Modification History ==================== The data were received as two flat ASCII tables (one each for IDS and LCS data), which were slightly reformatted to add the date of observation to each record. PDS labels were written by SBN personnel, and the table of observational parameters was keyed in and labeled to complement the two data tables. Parameters ========== The IDS data file lists the date, the offset, in RA and declination, of the slit from the optocenter (as measured at 5000 Angstroms), and the logarithmic offsets, column densities and error flags for each species of interest. Specific offsets are listed for each species because atmospheric dispersion causes slightly different regions of the coma to be observed at different wavelengths. The species listed in the IDS data file are C2 (two bands), CN, C3, CH and NH2. The LCS data file lists the same parameters for C2 (two bands) OH, NH, CN, C3 and CH. The observational parameters table lists geometric parameters for each of the observing dates in the data tables. These include the date, observation time range (UT), heliocentric distance and velocity, geocentric distance, plate scale at the comet, position angle of the anti-solar direction and comments regarding observing conditions and LCS slit orientation. Note that the data tables contain multiple entries for each observation date. These entries correspond to measurements from multiple spectra obtained during the listed range of times, as well as to different spatial positions along those spectra. Processing ========== The data were reduced in a standard manner, by removing the bias level from the CCD data and flat fielding to remove the pixel-to-pixel variations. Wavelength calibration was done using an argon lamp with the same instrumental setup used to observe the comet. Flux calibration was obtained via observations of standard stars. Sky measurements were obtained from a region of the sky well removed from the comet, to avoid cometary contaminations. These observations were used to remove the night sky contribution to the comet spectra. Underlying continuum (sunlight reflected from the dust) was removed in one of two ways. For some of the LCS data, a solar analogue star was observed, and used to remove the underlying continuum. For the IDS data and the rest of the LCS data, the solar spectrum from Arvesen et al. (Applied Optics 8, 2215, 1969) [ARVESENETAL1969] were convolved with the instrumental profile and removed from the comet spectrum. The extraction of the gas fluxes and column densities were performed as described in Cochran et al. (Icarus 98, 151 1992), [COCHRANETAL1992] using the conversion constants from that manuscript. Data ===== The data consist of three tables. The first table, OBSPARM.TAB describes the observational parameters relating to each of the observing runs in the data set. The other tables, IDS.TAB and CLS.TAB list the column densities at various locations in the coma. Media/Format ============ The data tables are given in the form of ASCII files. These tables do not use any sub-or super-script characters and so are readable in any format. The data set is available by electronic transfer. Spectra ======== The spectra used for measuring the column densities have not yet been submitted to the PDS for archiving. They have been requested, but are awaiting sufficient resources to complete their preparation. If and when the spectra become available, this data set will be updated to include them. Any researcher interested in using the spectra should contact Anita Cochran directly (Anita Cochran, Department of Astronomy, University of Texas, 78712). Review ====== This data set was peer-reviewed on 6 December 2002. Limitations =========== There are no uncertainties quoted on the column density measurements, but three grades are used to denote the quality of the measurements. First, no footnote on a measurement means it is a good quality result. A colon (:) following the column density indicates that the result is less certain (estimated to have up to 50% larger uncertainties), and two colons (::) indicate that the measurement is much less certain (as much as 100% higher uncertainties). The uncertainties are dependent on the particular molecule of interest, but for the high quality measurements, the random errors are 5-10%, with absolute errors ranging from 10-25%. The systematic errors very much depend on the molecule because if the wrong oscillator strengths are being used, then the result could be off by a factor of 2. However, this would affect all data for a given species in the same way. References ========== Cochran, A.L., E.S.Barker, and A.D.Storrs, The McDonald Observatory Faint Comet Survey: Gas Production in 17 Comets, Icarus, 98, 151, 1992. Cochran, A.L. and E.S. Barker, McDonald Observatory Spectral Observations of Comet 19P/Borrelly, Icarus, 141, 307, 1999. Arvesen, J.C., R.J. Griffin, Jr., and B.D. Pearson, Jr., Determination of extraterrestrial solar spectra irradiance from a research aircraft. Appl. Opt. 8, 2215-2232, 1969.