***** 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