***** File AAREADME.TXT This compact disc (CD-ROM) contains wide-field images of Halley's Comet obtained by the Large-Scale Phenomena Network (LSPN) of the International Halley Watch (IHW). The data have been collected, archived, processed, and prepared for deposit on CD-ROM by the Large-Scale Phenomena (L-SP) Discipline Specialist Team at the NASA/Goddard Space Flight Center, in cooperation with the IHW Lead Center at the Jet Propulsion Laboratory and the National Space Science Data Center (NSSDC) at NASA/GSFC. This disc is one in a series of compressed image discs dedicated to IHW/L-SP imagery, the series itself being a subset of the total IHW CD-ROM archive of 30,000 ground-based observations of Comet Halley. Chronological data from the IHW Disciplines reside together on a shorter series of multi-discipline CD-ROMs. The IHW began operations, with NASA funding, in 1982. A total of 1,439 digital images of Comet Halley are stored on a series of L-SP compressed data CD-ROMs, as well as 173 images of various calibration objects. This specific disc contains 145 images of Halley's Comet spanning the time period 1985 September 21 to December 7, and 14 calibration images associated with a subset of the Halley data. The total volume of data on this CD-ROM is 635 Mbytes. This file is the only text file that is in the root directory. A listing of the contents of the subdirectories for the CD-ROM follows: BROWSE - subsampled browse images (extension = .IBG), with FITS headers (.HDR) and PDS labels (.LBL) C85SEP21 - Halley compressed image data (.IMQ), with FITS headers and PDS labels CALIB - calibration data, compressed (.IMQ), with FITS headers and PDS labels DOCUMENT - supporting text files EPHEM - ephemeris data for the comet INDEX - delimited index tables to aid in locating data SOFTWARE - supporting source and executable code An illustration of the subdirectory structure of this CD-ROM is given in the file CDTREE.TXT, located in the DOCUMENT subdirectory. All .TXT files are fixed length ASCII text (80 bytes including characters at the end of each line). To show specific content, some files have been given extensions as follows: .C - C source code .COM - executable file for MS-DOS .EXE - executable file (on this disc, either VAX/VMS or MS-DOS) .FOR - Fortran source code .IDX - delimited table file .PRO - Interactive Data Language (IDL) procedure file The use of other file extensions (particularly in the INDEX subdirectory) are considered to be a common practice for dBASE files, e.g., .DBF. Some specialized information about other subdirectories is given in the explanatory files below: BRWZINFO.TXT - description of the browse files and their structure CALINFO.TXT - description of the calibration data files COMPINFO.TXT - explanation of the compressed image data files INDXINFO.TXT - description of how to use the table data SOFTINFO.TXT - listing of the software information supplied There are two special text files in the DOCUMENT directory that give an overview to the entire volume: IMAGUIDE.TXT and CDSTRUCT.TXT. The latter has been used to construct the file VOLDESC.SFD located in the root directory. This file contains general information similar to what you are reading now but formulated according to guidelines put forward by the Consultative Committee on Space Data Systems (CCSDS) for easier access by computers. M. Aronsson E. Grayzeck, Jr. D. Klinglesmith III IHW Software Specialist National Space Science IHW Team Member for for the Lead Center Data Center Large-Scale Phenomena Jet Propulsion Interferometrics, Inc Laboratory for Astronomy Laboratory and Solar Physics Mail Stop 169-237 Code 633 Code 684.0 4800 Oak Grove Dr. NASA/GSFC NASA/GSFC Pasadena, CA Greenbelt, MD Greenbelt, MD 91109 20771 20771 M. Niedner, Jr. A. Warnock III IHW Discipline Specialist for IHW Team Member for Large-Scale Phenomena Large-Scale Phenomena Laboratory for Astronomy ST Systems Corp and Solar Physics Code 684.1 Code 681 NASA/GSFC NASA/GSFC Greenbelt, MD Greenbelt, MD 20771 20771