SPECTROSCOPY AND SPECTROPHOTOMETRY NETWORK This directory contains the digital appendices for the Spectroscopic and Spectrophotometry Network (SSN) for the International Halley Watch. The files included are described below. o SP_CODE.* - This is a set of files which contain and describe a table to translate the DIS-CODE keyword into its meaningful parts. There is a description file (.TXT), a delimited file (.TAB), a table header file (.STR), a FITS header (.FIT, blocked for 2880 bytes), and a "readable" FITS header (.HHH, blocked for 80 bytes). This table is intended for entry into a database program for use. o SP_HISTO.* - This is a histogram of number of spectra in archive vs date. The data (.DAT) is a two column ASCII file. There is a description file as well (.TXT). I. INTRODUCTION The 1985 apparition of comet P/Giacobini-Zinner became historical with the success of the U.S. International Cometary Explorer (ICE), the first space- craft mission to a comet. On 11 September 1985, six days after perihelion, the ICE spacecraft passed through the coma, approaching to within 7800 km of the comet's nucleus. Spectroscopic observations obtained while the ICE spacecraft transited the coma are included in the IHW Spectroscopy and Spectrophotometry Network (SSN) archive together with good coverage of spectra obtained both before and after perihelion. The personnel of the Discipline Specialist Team of the Spectroscopy and Spectrophotometry Network is listed in Table I. The Center collected 433 spectra of the comet and associated calibration spectra. The completed spectro- scopic archive includes observations that cover the period from 6 months prior to perihelion to 4 months after perihelion, which corresponds to heliocentric distances of 2.3 and 1.6 AU, respectively. Table I. Discipline Specialist Team of the Spectroscopy and Spectrophotometry Network ________________________________________________________________________________ Team Member Affiliation Responsibility ________________________________________________________________________________ Susan Wyckoff Physics Department Discipline Specialist Arizona State University Tempe, AZ 85281 U.S.A. Peter A. Wehinger Physics Department Discipline Specialist Arizona State University Michel Festou Observatoire de Besancon Discipline Specialist F-2544 Besancon Cedex France Beverly Dunlap Physics Department Office Manager & Data Assistant Arizona State University Anthony J. Ferro Physics Department Scientific Programmer & Data Arizona State University Assistant Gregory Loper Physics Department Archivist & Data Cataloguer Arizona State University ________________________________________________________________________________ The detectors used to record the spectra in the archive include a microchannel plate with output recorded on photographic film, an SEC Vidicon for IUE data, a scanning photoelectric scanner, an image dissector scanner, and several different charge-coupled devices (CCDs). The spectrographs were all located at the Cassegrain foci of telescopes which ranged in aperture from 2 to 4 meters, situated in both the northern and southern hemispheres. Ten percent of the archive data were obtained with CCDs and are in two-dimensional format. The Discipline Specialist Team requested that the spectroscopic obser- vations be submitted in FITS format, and both flux and wavelength calibrated. Most submitters complied with this request. The FITS headers identify the spectra in the archive that are not in the SSN standard units (ergs cm-2 s-1 Angstrom-1 for flux, and Angstrom units for wavelength), or are not calibrated. The archive appears in two forms, printed and digital. In the printed version, the temporal distribution of the observations is presented in Fig. 1. In the digital version, this figure can be generated from information in the file HISTO.* (cf. Sec. III). II. THE PRINTED ARCHIVE The printed archive is a hard-copy volume which contains a one-line description of each spectrum extracted from the digital archive (Sec. III). The column headings given for each spectrum in the printed archive are described in Table II. Table II. Entries in the Printed Archive ________________________________________________________________________________ Heading Description ________________________________________________________________________________ Date(UT) Date (day & fraction of day) of middle of observation [UT]. Same as FITS keywords DATE-OBS and TIME-OBS. SSN# A running number for each observation, where initial digit 7 identifies the Spectroscopy and Spectrophotometry Network. Same as FITS keyword FILE-NUM. Resol Approximate spectral resolution [Angstrom]. Same as FITS keyword RESOL-SP. Range Approximate spectral range [Angstrom]. Same as FITS keyword RANGE-SP. ExpS Exposure or integration time of observation [s]. Same as FITS keyword EXPOSURE. DiscCode Discipline specific code. This is a 9 digit number giving coded information about the observation. The detector number, the instrument number (both assigned by the SSN), the wavelength region, the approximate spectral resolution and the quality of the data are encoded as DDCCWWWRQ where: DD = detector number CC = instrument configuration number WWW = wavelength region included. A binary coding scheme has been used to specify a unique number for a wavelength region. This number is the sum of all defined values from the table below for each spectral region present. The defined values and the corresponding wavelength regions [A] are: 1 = < 3000 2 = 3000 - 3499 4 = 3500 - 3999 8 = 4000 - 4999 16 = 5000 - 5999 32 = 6000 - 6999 64 = 7000 - 7999 128 = 8000 - 10000 256 = > 10000 Example: for 3200-6900 A, WWW = 2+4+8+16+32 = 062. R = spectral resolution. This digit is assigned a value based on the corresponding spectral resolutions (FWHM in A) given below: 1 = <= 0.05 2 = > 0.05 - 0.2 3 = > 0.2 - 1 4 = > 1 - 5 5 = > 5 - 10 6 = > 10 - 20 7 = > 20 - 50 8 = > 50 - 100 9 = > 100 Q = quality of the data. A subjective judgement on the quality of the data is taken from the QUALITY keyword. The following values are assigned: 0 = Unknown 1 = Excellent 2 = Very Good 3 = Good 4 = Fair 5 = Poor Typ Data type. Same as FITS keyword DAT-TYPE. One of the following: U = Unknown R = Reduced Digital X = Raw Digital P = Photographic O = Objective Prism I = Interferometer S = Space Borne Slit Aperture diameter (for a circular slit) or slit width and length (for a rectangular slit) given [arcsec]. Same as FITS keyword APERSIZE. PAs Position angle of slit, measured north through east [deg]. Same as FITS keyword POSANG. Airm Airmass of observation, followed by a character to indicate whether its value is for beginning (B), middle (M), end (E), average (A) of observation. Same as FITS keywords AIRM-BEG, AIRM-MID, AIRM-END, and AIRM-AVE. N Number of axes in data. Same as FITS keyword NAXIS. n(lambda) Number of pixels in wavelength direction. Same as FITS key- word NAXIS1. n(y) Number of pixels in spatial direction. Same as FITS keyword NAXIS2. C Code for type of first independent variable. Same as FITS keyword CTYPE1. 1 = Angstrom 2 = Velocity [km/s] 3 = Pixel number 4 = Projected distance [arcsec] 5 = Other (described in COMMENT filed in header) B Code for type of dependent variable. Same as FITS keyword BUNIT. 1 = Flux per wavelength interval 2 = Flux per frequency interval 3 = Flux in Rayleighs per Angstrom unit 4 = Relative intensity 5 = Counts or counts per second 6 = Density 7 = Other (described in COMMENT field in header) Offset rho Separation between center of slit or aperture and center of nucleus [arcsec]. Offset theta Orientation of the slit center with respect to the center of the nucleus, measured from north through east [deg]. Same as FITS keyword ORIENT. System System station code. This is an eight digit number. The first digit is the IHW network number, followed by the 3-digit IAU observatory number, a 2-digit telescope number assigned by the Large Scale Phenomena Network, and an instrument/detector number assigned by the SSN. Same as FITS keyword SYSTEM. Observer(s) The main observer(s) during the observation. Same as FITS keyword OBSERVER Notes This field indicates if there are any special notes about the observation. Same as FITS keyword COMMENT NOTE. ________________________________________________________________________________ Representative spectra of comet P/Giacobini-Zinner are also included in the printed archive. The data submitted to the SSN Network were of two basic types, one- or two-dimensional spectra. The one-dimensional spectra are presented as plots of flux vs. wavelength. The two-dimensional spectra are presented as gray-scale images in the printed archive. Approximately 10 percent of the SSN data is in form of two-dimensional spectra obtained with long-slit spectrographs. III. DIGITAL ARCHIVE The digital archive on the CD-ROM laser disk contains all of the spectroscopic data of comet P/Giacobini-Zinner together with related appendices and a table. Each archived spectrum (one- or two-dimensional) consists of a set of three files: 1. A Planetary Data System (PDS) header -- a short header describing the data file, so that PDS software can be used to display the archived data. Note that only minimal header information is included in this file. 2. Flexible Image Transport System (FITS) header -- a longer header in FITS format (Wells et al. 1981). The FITS header contains both standard keywords as well as keywords specific to the IHW-SSN. The FITS keywords are described below and in the digital files INTRO.TXT (this writeup) and CODE.*. The purpose of the FITS header is to describe the data contained in the associated file. Programs such as the Image Reduction and Analysis Facility (IRAF) developed at the National Optical Astronomy Observatories (NOAO) can be used to display and analyze the FITS formated archive data. 3. Data -- the data in the form of an integer byte stream are in the associated data file. To aid users of the digital archive on the CD-ROM disk in examining the contents of the SSN data, several descriptive appendices and tables have been included in the digital version of the archive. The appendices include statistics on the number of spectra in the archive (HISTO.*), as well as this file (INTRO.TXT). In addition a set of files is included in the digital archive (CODE.*), which translates the FITS header keyword DIS-CODE and which presents the archive user with files that facilitate the use of data base programs to examine the contents of the archive. The appendices and the de-coding table are described in Table III and more fully in the appropriate digital files: Table III. Description of Appendices to Digital Archive ________________________________________________________________________________ File Contents ________________________________________________________________________________ AAREADME.TXT General description and table of contents of the digital files which consist of the SSN appendices, and the DIS-CODE table, together with its associated files. INTRO.TXT Copy of this writeup. HISTO.* Statistical compilation of the number of spectra of P/Giacobini- Zinner included in the archive and the times of observation. This file can be used to construct a histogram for the obser- vational coverage of the SSN. CODE.* Set of files which describe and translate the FITS keyword DIS-CODE. The purpose of including this keyword in the header for each spectrum in the archive is to facilitate data base program searches of the spectra. The DIS-CODE keyword is a 9-digit coded integer which contains information about the instrumentation used to obtain the spectrum, the wavelength range, aperture size and the spectral resolution, as well as the quality of the spectrum. DIS-CODE is described fully below, and files are given in CODE.* to aid translating DIS-CODE by entering it into data base programs. The CODE.TAB file lists the translations of the DIS-CODE keyword in tabular form. The DIS-CODE keyword is defined by information provided in the FITS header of any spectrum. The table contained in CODE.TAB is formatted for ease of use in data base programs (as a delimited format table). As an aid for using CODE.TAB in data base programs, another file is provided, CODE.STR, which may be used to define a DIS-CODE table format in a data base program. The CODE.STR file contains a data base format that gives the column heading entry type (character, numerical or date), the column widths and the number of decimal places for using a data base program to display the table in CODE.TAB. A header file CODE.FIT for the CODE.TAB file is also supplied, which when attached to the data in CODE.TAB provides a header in standard FITS format. The file CODE.HHH contains the same data as the CODE.FIT file, but has 80 byte records (as opposed to 2880 for the CODE.FIT file). This is to allow easy display of the file. ________________________________________________________________________________ IV. DESCRIPTION OF IHW-SSN FITS KEYWORDS Table IV describes the keywords used in the FITS headers of the SSN data. Each keyword is listed in capital letters, followed by an initial that indicates whether the variable is a logical (L), integer (I), floating point (F), or character string (C). For several FITS keywords, there are several forms of the keyword, usually relating to various axes. In these cases, the keyword is listed as XXXXn, where n is the number of the axis which the keyword describes. Table IV. Keywords in the FITS headers ________________________________________________________________________________ Keyword Type Description ________________________________________________________________________________ SIMPLE L Does the file conform to the FITS format? If yes, the keyword is set to T. Otherwise the keyword is F. This keyword should be set to true for all SSN files. BITPIX I Keyword contains the number of bits in each pixel. This value is either 16 or 32 for SSN data. NAXIS I Keyword contains the number of axes in the data: 1-dimensional spectra have a value of 1, 2-dimensional spectra a value of 2. NAXISn I n is a number in the range of 1 to NAXIS. Keyword contains the length of axis. NAXIS1 is the dimension of the fastest varying axis in the data. NAXIS2 is the second fastest varying axis, etc. EXTEND L Does the file contain extensions conforming to the FITS stan- dards? For all SSN data files, EXTEND = F (no extensions). OBJECT C Keyword contains the name of the object of the data. FILE-NUM I This is a running number of the files sent to the archive. All values have six places and, for the SSN, begin with 7. For P/Giacobini-Zinner, file numbers are in the range of 700100 to 700999. DATE-OBS C Universal Time [UT] date of middle of data acquisition. Date is given in the FITS standard of day, month, year (DD/MM/YY). TIME-OBS F Fractional part of day, indicating the UT time of the middle of data acquisition. The keyword has a value ranging from 0.0 to 0.99999. DATE-REL C Date the submitter or submitters agree to release their data to the public. DISCIPLN C IHW Discipline. For the SSN the value is always SPECTROSCOPY. LONG-OBS C East longitude of observation station. Keyword value range is from 00/00/00 to 359/59/59. LAT--OBS C Latitude of observation station. Degrees north or south are indicated by a preceding '+' or '-', respectively, 0 has no sign. SYSTEM C Station system code. Keyword is a number of the form 7nnnttii, where: 7 = Discipline number (SSN) nnn = IAU Observatory Number tt = Telescope Number, as assigned by the IHW Large Scale Phenomena Network (LSPN) ii = Instrument/Detector Number, assigned by the SSN, and corresponds to DD in DIS-CODE keyword OBSERVER C Name of observer. If more than two observers, first observer listed, followed by ET AL. Additional observers are listed in COMMENT ADD.OBS. keyword. SUBMITTR C Name of person or persons who submitted the data to the IHW SSN. SPEC-EVT L If true, some special event occurred during observation. See COMMENTs and HISTORYs for more information. DAT-FORM C Form of the data. One of: ASCII, STANDARD, HARDCOPY, NODATA. DAT-TYPE C Type of data being submitted. One of: UNKNOWN, REDUCED DIGITAL, RAW DIGITAL, PHOTOGRAPHIC, OBJECTIVE PRISM, INTERFEROMETRIC, SPACE BORNE. DIS-CODE C This keyword contains a 9-digit integer with the digits defined as DDCCWWWRQ, where: DD = Detector/Instrument combination. This is a unique number for each combination and has been assigned by the SSN. This value is the same as ii in the SYSTEM code. CC = Configuration (grating, grating tilt, filter, aperture size, order, etc.) for given telescope and detector/instru- ment combination. WWW = Wavelength range [Angstrom], included in data. A binary coding scheme is used to specify a unique number for a unique set of wavelength regions. The number is the sum of all defined values for each spectral region in which data are submitted: 1 = <3000 2 = 3000-3499 4 = 3500-3999 8 = 4000-4999 16 = 5000-5999 32 = 6000-6999 64 = 7000-7999 128 = 8000-10000 256 = >10000 Example: for 3700-6400 A, WWW = 4+8+16+32 = 60. R = Resolution. This parameter is based on the spectral resolution (FWHM in Angstrom). 1 = <= 0.05 2 = > 0.05 - 0.2 3 = > 0.2 - 1 4 = > 1 - 5 5 = > 5 - 10 6 = > 10 - 20 7 = > 20 - 50 8 = > 50 - 100 9 = > 100 Q = Quality of the data. We adopted a qualitative judgement for this parameter, and the values are the same as the QUALITY keyword. 0 = Unknown 1 = Excellent 2 = Very Good 3 = Good 4 = Fair 5 = Poor The files CODE.* contain a full listing of the discipline codes used for P/Giacobini-Zinner, as well as the components which define the DIS-CODE values. These files may be read into a database program, and used to translate DIS-CODE values. OBSVTORY C Name of observatory from which data were obtained. ELEV-OBS F Elevation of the observing station [m]. TELESCOP C Telescope used for observation. Where possible, the telescope name as listed in the Astronomical Almanac has been used. INSTRUME C Instrument and detector used to obtain data. RESOL-SP C Approximate spectral resolution of data [Angstrom]. RANGE-SP C Approximate spectral range of data [Angstrom]. EXPOSURE F Exposure or integration time [s]. APERSIZE C Entrance aperture size or slit width and length of instrument or detector [arcsec]. Airmass F One of the following: AIRM-BEG = Airmass at beginning of observation. AIRM-END = Airmass at end of observation. AIRM-MID = Airmass at midpoint of observation. AIRM-AVE = Average of airmass of observation. SEPNUC F Separation between the comet nucleus and center of slit or aperture [arcsec]; see Fig. 2. ORIENT F Position angle of slit or aperture center with respect to the comet's nucleus, measured north through east, ranging from 0 to 360 deg; see Fig. 2. N ORIENT ^ | | | | POSANG | /| Tail \ N |/ | / E <--- \ ^ ( *======= \ | \/ \ \ | / Nucleus \ \| / \^| /------ SEPNUC \|/ Slit Center ------\ \ \---- Slit \ Fig. 2. Definition of angles. POSANG F Position angle of the slit measured north through east, ranging from 0 to 360 deg. Two-dimensional spectra only (Fig. 2). See COMMENT and HISTORY sections for observers' variations of this definition. PIXSCALE F Image scale at detector [arcsec per pixel]. Two-dimensional spectra only. QUALITY I A subjective, qualitative estimate of the data. Values used: UNKNOWN, EXCELLENT, VERY GOOD, GOOD, FAIR, and POOR. CTYPEn C n is a number between 1 and NAXIS. Name of the independent variables: LAMBDAA = Wavelength [Angstrom]. VELOCITY = Velocity [km/s]. PIXELS = Pixel number. RHO = Projected distance [arcsec]. OTHER = Described in a comment. BUNIT C Name of dependent variable: FLAMBDA = Flux per wavelength [erg/cm2/s/Angstrom]. FNU = Flux per frequency [erg/cm2/s/Hz]. RAYLAMBDA = Flux per wavelength [Rayleighs/Angstrom]. RELINS = Relative intensity. COUNTS = Counts or count rate [counts/s]. DENSITY = Photographic density. OTHER = Described in a comment. CRVALn F Reference point for CTYPEn. CRPIXn F Reference pixel location corresponding to CRVALn. CDELTn F Increment in CTYPEn per pixel. ________________________________________________________________________________ In addition the FITS headers include a number of HISTORY, COMMENT, and related keywords. They are listed in Table V. Table V. HISTORY, COMMENT, and related keywords in the FITS headers ________________________________________________________________________________ Keyword Type Description ________________________________________________________________________________ HISTORY DATE-REC C Date the file was received by the SSN. HISTORY DATE-CMP C Date of completion of the file archiving. HISTORY REDUCED C Known data reduction steps. HISTORY C Other history if known. COMMENT ADD.OBS. C Additional observers. COMMENT NOTE C Some important note on the data extracted from COMMENT or HISTORY fields to appear in the printed archive listing. COMMENT PROC FILE and ORIG. FILE C Comment regarding original file identifi- cation of the submitted file. Often file name consists of position of file on original submission tape. Used for SSN archiving. COMMENT REPLACE C A note that this file supercedes another file (previous file would have been deleted from the archive). COMMENT C Additional comments about the data. DATAMAX F Maximum value of dependent variable. DATAMIN F Minimum value of dependent variable. BSCALE F Scale factor to convert FITS pixel values to true values. Used to convert FITS data to original data values: DataValue = BZERO + BSCALE*FileDataValue BZERO F Offset applied to true pixel values. END C Signals end of FITS header. ________________________________________________________________________________ V. SSN OBSERVERS This archive was made possible thanks to the contributions by the 27 participating observers from three countries. The names and affiliations of these observers are listed in Table VI. Table VI. List of Observers ________________________________________________________________________________ Observer Affiliation Country ________________________________________________________________________________ A'Hearn, M. University of Maryland U.S.A. Barker, E. University of Texas at Austin U.S.A. Belton, M. Kitt Peak National Observatory/NOAO U.S.A. Boehnhardt, H. Max-Planck-Institut fuer Aeronomie Federal Republic Germany Cochran, A. University of Texas at Austin U.S.A. Cochran, Wm. University of Texas at Austin U.S.A. DiSanti, M. LPL, University of Arizona U.S.A. Feldman, P. Johns Hopkins University U.S.A. Festou, M. Observatoire de Besancon France Filippenko, A. University of California at Berkeley U.S.A. Fink, U. LPL, University of Arizona U.S.A. Green, J. University of Texas at Austin U.S.A. Konno, I. Arizona State University U.S.A. Larson, S. LPL, University of Arizona U.S.A. Lutz, B. Lowell Observatory U.S.A. McCarthy, P. Las Campanas/Mt. Wilson Observatories U.S.A. McFadden, L. University of California at San Diego U.S.A. O'Dell, C.R. Rice University U.S.A. Sargent, W. Palomar Observatory, Caltech U.S.A. Sawyer, S. University of Texas at Austin U.S.A. Sonneborn, G. NASA Goddard Space Flight Center U.S.A. Spinrad, H. University of California at Berkeley U.S.A. Strauss, M. University of California at Berkeley U.S.A. Tegler, S. Arizona State University U.S.A. Wagner, R.M. Lowell Observatory U.S.A. Wehinger, P. Arizona State University U.S.A. Wyckoff, S. Arizona State University U.S.A. ________________________________________________________________________________ ACKNOWLEDGMENTS Besides the members of the Discipline Specialist Team (Table I), the following individuals also participated in archiving the SSN P/Giacobini-Zinner data. They contributed greatly to the completion of the archive: K. Byard, L. Engel, I. Kono, E. Lindholm, L. McKibben, B. Pfarr, D. Reisinger, D. Schleicher, S. Tegler, J. Theobald, R.M. Wagner, and M. Womack. 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