***** File CROMGUID.TXT Comet Crommelin User's Guide to the Compact Disc Read Only Memory E. Grayzeck (NSSDC - NASA/GSFC) A. Warnock (LSPN - NASA/GSFC) M. Aronsson (IHW - JPL) Contents 1. Background and Scope of Compact Disc 2. Accessing the Disc 3. Data Products 4. Directory Structure 5. Filenaming Convention 6. Available Software 7. Reference 1. BACKGROUND AND SCOPE OF COMPACT DISC The CROMMELN sub-directory of this compact disc contains observations of comet Crommelin from the apparition of 1983-84. During that period, the International Halley Watch (IHW) mounted a campaign to observe the comet as a trial run in order to test out the different parts of the IHW organization. The data from that apparition form a database which is being placed on this compact disc. Since this first effort by the IHW wasn't originally intended for inclusion on compact disc, the more sophisticated aspects of archiving on CD-ROM are not included for this comet. 2. ACCESSING THE DISC These discs have been manufactured following the normal specifications for Compact Disc Read Only Memory (CD-ROM) as well as the logical structure outlined by the International Standards Organization (ISO) in the No. 9660 document. A basic system requirement demands that the CD-ROM reader and software driver support this standard. At this writing (July 1990), primary access to the disc will be using IBM-PC or compatible computers. However, software support from vendors for the Apple MacIntosh II and some workstations (SUN, MicroVAX) is now available. If you are using a PC style machine, the reader that you bought should include the appropriate hardware (a PC-bus or SCSI controller board and cable) and software to address your device. Software packages should include a device driver for your machine and extensions to DOS that allow the reader to "look" like another random access disk drive; the de facto standard here is the Microsoft Extensions (MSCDEX 2.0 or higher). Install the specific device driver software as directed by the documentation accompanying the hardware. Usually, this will involve specifying the device driver in a DEVICE= line in the CONFIG.SYS file and invoke the extensions package from your AUTOEXEC.BAT file. This will automatically configure the CD-ROM reader when the computer is booted. Remember that the CD-ROM reader is assigned a drive name which you have either chosen with the appropriate command line switch (/L:H assigns the CD- ROM reader to drive H:) or allowed to default to the next available device letter in your system. Typical PC configurations will have two floppies (A: and B:), and a hard disk (C:). Put your drive at some letter higher than that. Remember that many DOS commands work on the CD-ROM but that it is a read-only medium. Some of the useful DOS functions are: DIR - directory listing CHDIR - change directory (also CD) TYPE - list the contents of a file on the screen; useful for normal text with , delimiters COPY - copy file(s) to another device PRINT - print file on hard copy device Notice that commands such as DEL and MKDIR are not available since the CD-ROM is a read-only medium. Furthermore, some compact disc software packages will invoke screen plots that may depend on the DOS program GRAPHICS.COM. In this case, execute it in your AUTOEXEC.BAT file or before you run the software package. There has been no attempt made to split the files in the CROMMELN sub- directory into header files and data files. The files have been included in their original form (in the FITS format) with the filename extension .FIT. The user will not find any PDS labels describing these files. 3. DATA PRODUCTS A large number of scientists have contributed to this archive project. The contributing observatories, with their IHW system codes, are summarized in a separate file (CR_OBSCD.TXT). Individual observers and their various instruments are identified in the header that accompanies the data. The ground-based data is located in separate directories for each discipline (named AMATEUR, ASTROM, INFRARED, LS_PHEN, NEAR_NUC, PHOTOM, RADIO, and SPECTR). Within each directory, the files are given in chronological order. As opposed to the cases of P/G-Z and P/Halley, the LSPN images for P/Crommelin are included in the original, uncompressed form. Some networks have submitted supplemental data which include filter tables and non-comet images. These are stored in the CALIB subdirectory and except for the Infrared Filter Tables (IRFT) also appear in the chronological directories. 4. DIRECTORY STRUCTURE The volume and directory structure of this disk conform to the Level-1 standard specified by the ISO. This format is widely accepted and used on a variety of machines. The AAREADME.TXT file in the root directory introduces the user to the full extent of the archive and the contents of the individual subdirectories. There are two directories (DOCUMENT and INDEX) below the CROMMELN sub- directory that contain supplementary files. In addition, to correlate the chronological observations with physical location of the comet, some recent ephemeris information has been included (in the subdirectory EPHEM). The DOCUMENT subdirectory contains the text files from the directories CALIB, EPHEM, and INDEX, the file CR_OBSCD.TXT, as well as this file (CROMGUID.TXT). Further information can be found in the general DOCUMENT sub- directory (under the root directory; originally intended for P/G-Z, but in many cases applicable to P/Crommelin as well). Additional information about comet Crommelin can also be found in the printed volume "Archive of Observations of Periodic Comet Crommelin". The index information included for P/Crommelin is not as sophisticated as the index information included for comets G-Z and Halley. The CSUMINDX.TAB table can be used as a Quick Look index and the CROMINDX.TAB table can be used as a more complete index. Further information is contained in the file CR_INDEX.TXT and at the beginning of each index table. 5. FILENAMING CONVENTION The International Halley Watch agreed early on in the project that all data would be submitted from the individual disciplines to the Lead Center using the FITS format. Unlike the data included elsewhere of comets G-Z and Halley, the data for P/Crommelin remain in the original, complete FITS files. The convention for naming files on the CD-ROM was proposed by the IHW Lead Center to include a unique data qualifier for the data. A specific set of rules was established to identify the network/subnetwork for each discipline (given by a letter code). A CD-ROM running number, starting at 9001, relates the information contained in the various indexes to the files. In the case of calibration data, the same network/subnetwork code is used but the number starts at 9901. A short list organized by Discipline (Number) and listing network/subnetwork is given below: Discipline Number Subnet (Exp) Letter Code Astrometry 1 none ASTR Infrared Studies 2 Photometry IRPH Filter Table IRFT Large-Scale Phenomena 3 none LSPN Near Nucleus Studies 4 none NNSN Photometry Polarimetry 5 Broad Band Mag PMAG Narrow Band Flux PFLX Polarimetry PPOL Radio Studies 6 Continuum RSCN OH RSOH Spectral Line RSSL Spectroscopy Spectrophot 7 none SPEC Amateur Observations 8 Visual Magnitude AMV All files have the extension .FIT. 6. AVAILABLE SOFTWARE We have designed the data formats to be compatible with many existing packages and plan to distribute two public domain packages, IMDISP (from JPL) and FITSREAD (from the ADC) on an accompanying floppy disk. 7. REFERENCE "Archive of Observations of Periodic Comet Crommelin, Made During Its 1983-84 Apparition", Z. Sekanina, Editor, M. Aronsson, Software Specialist, JPL Publication 86-2.