***** File PREFACE.TXT PREFACE The International Halley Watch (IHW) grew out of a National Aeronautics and Space Administration (NASA) sponsored study in 1979-80 led by Louis Friedman of the Jet Propulsion Laboratory (JPL). The premise behind that study was that some form of cooperation among the astronomers and space scientists of the world would be necessary to make the most of the once per lifetime opportunity to study Comet Halley. It was obvious that international cooperation required sponsorship by the International Astronomical Union (IAU), and that had to be obtained at the 1982 General Assembly of the IAU or preparations could not be ready in time for Halley. This set the timing for creation of the entire IHW organization. In 1980 NASA organized a Lead Center for the western hemisphere at JPL under Ray Newburn. A similar facility for the eastern hemisphere was organized at the Dr. Remeis Sternwarte, Bamberg, under Juergen Rahe with the support of the government of the Federal Republic of Germany. Newburn and Rahe elaborated upon the plans of the original study group, which suggested appointment of specialists to set up networks of observers in each of the major observing disciplines, establishment of an international oversight committee, coordination with the planned space projects, and cooperation with amateur observers. In 1981 a Steering Group of 22 scientists resident in 12 countries was appointed by NASA to help establish the individual discipline organizations and to advise on IHW operations. Later this international group became independent of NASA, elected its own chairman, and added and/or replaced members as it felt necessary. The Steering Group selected Discipline Specialists, based on formal proposals submitted in response to a NASA letter, mailed worldwide, seeking cometary scientists to organize the observing networks, coordinate their activities, and later to assist in archiving the resulting data. By the time of the 1982 IAU meeting, a complete administrative organization was in existence, awaiting its acceptance and imprimatur by that worldwide group. The original study at JPL suggested that the most important product of the IHW should be an archive of all the data. The archive was not to replace the normal interpretation and publication in technical journals. Rather it was to complement those publications by establishing a comprehensive database suitable for further studies requiring reduced but uninterpreted data from many observers and different disciplines. The complete archive would be given to each observer contributing to it and made available to institutes worldwide. Cost of this publication would be borne by NASA. Initially this was envisioned as a printed archive. Almost immediately it became obvious that, to maintain full quantitative accuracy, a digital version of the archive would be necessary. The logic leading to the selection of CD-ROMs (Compact Disc - Read Only Memory) as the digital medium is presented elsewhere. In 1981 Newburn and Rahe presented the IHW idea to the first joint meeting of the space agencies planning to send probes to Halley. That meeting led to a permanent organization known as the Interagency Consultative Group (IACG). The IACG was especially interested in the proposed Astrometry Network of the IHW as a possible source of data for their spacecraft navigation, and the IHW continued to be represented at IACG meetings as long as their primary agenda item was Halley. When NASA decided to shift its ISEE (International Sun-Earth Explorer) spacecraft into a trajectory encountering Comet Giacobini-Zinner (G-Z) and renamed it ICE (International Comet Explorer), it was natural to request that observations of G-Z be coordinated by the IHW as well, and this was done. In publishing the archive there seemed to be no good reason to mix G-Z data with those of Halley. Further, with the G-Z observations completed much earlier than those of Halley, publication of a separate "G-Z Archive" would offer a chance to make a final test of the end-to-end data handling capabilities of the IHW. All IHW software necessary for Halley therefore was utilized to produce 100 test CDs of the G-Z data. The copies of the test disc were used by various concerned scientists in the same way as they anticipated use would be made of the final Halley archive discs. They tested its structure and indices and its readability and accessibility. As a result of the tests some changes were made, for example in the file naming conventions. A final version of the G-Z disc has now been assembled; since there was room on the disc, data taken on Comet Crommelin during a 1984 test of the IHW network was included. The Halley discs are of three types: Volumes 1-18 contain compressed wide-field images from the Large-Scale Phenomena (L-SP) Discipline, Volumes 19-23 are comprised of data from all the IHW ground-based Disciplines (the L-SP data being highly subsampled), and Volumes 25-26, still in preparation, contain space data from the Halley probes and the ICE. Volume 24 is the final G-Z disc. The 23 Halley ground-based discs are the result of a long developmental process. The final steps of disc production involved the loading of all IHW data onto the NASA/Goddard Space Flight Center IBM mass storage system, and the transfer of directory-grouped datafiles to the CD-ROM pre-mastering workstation at the NASA/GSFC National Space Science Data Center (NSSDC). As final checks for errors and "reasonableness" of disc design and content, 80 L-SP images were deposited on one test disc (testing the concepts of Volumes 1-18), and a representative sample of the other ground-based data was deposited on a second test CD-ROM (testing Volumes 19-23). One hundred copies were made of each test disc. This check by Ed Grayzeck, Dan Klinglesmith, Malcolm Niedner, and Archie Warnock at NASA/GSFC, and by several other reviewers, and further checks at JPL by Mikael Aronsson while producing a camera-ready hardcopy, uncovered some errors, all of which have been corrected or are noted in errata files. We hope this extensive effort has led to a package of use to many scientists. At this writing no absolute decision has yet been made as to whether there will be a printed archive as well as the digital archive. A printed archive would be useful to many people, but it also would be more expensive to print, bind, and distribute than it has been to produce the CD archive. Camera ready copy for a printed archive is being produced, and the books will be printed if possible, perhaps as a NASA contribution to the International Space Year. Ray L. Newburn, Jr. Juergen Rahe Leaders, International Halley Watch October 1, 1991