Voyage to Jupiter

Produced by Stephen Hutcheson and the Online Distributed
Proofreading Team at http://www.pgdp.net






    [Illustration: A special color reconstruction of the eruption of the
    volcano Loki on the Jovian satellite Io. The picture was taken by
    Voyager 1 from a range of about half a million kilometers.
    [P-21334C]]




                                                             NASA SP-439

    [Illustration: Voyage To Jupiter]




                           Voyage To Jupiter


                             David Morrison
                             and Jane Samz

    [Illustration: NASA]

          Scientific and Technical Information Branch    1980
             National Aeronautics and Space Administration
                                                          Washington, DC
  For sale by the Superintendent of Documents
  U.S. Government Printing Office, Washington, D.C. 20402
  Library of Congress Catalog Card Number 80-600126




                                FOREWORD


Few missions of planetary exploration have provided such rewards of
insight and surprise as the Voyager flybys of Jupiter. Those who were
fortunate enough to be with the science teams during those weeks will
long remember the experience; it was like being in the crow’s nest of a
ship during landfall and passage through an archipelago of strange
islands. We had known that Jupiter would be remarkable, for man had been
studying it for centuries, but we were far from prepared for the torrent
of new information that the Voyagers poured back to Earth.

Some of the spirit of excitement and connection is captured in this
volume. Its senior author was a member of the Imaging Team. It is not
common that a person can both “do science” at the leading edge and also
present so vivid an inside picture of a remarkable moment in the history
of space exploration.

  April 30, 1980
                                                         Thomas A. Mutch
                                                 Associate Administrator
                                                 Office of Space Science




                              INTRODUCTION


The two Voyager encounters with Jupiter were periods unparalleled in
degree and diversity of discovery. We had, of course, expected a number
of discoveries because we had never before been able to study in detail
the atmospheric motions on a planet that is a giant spinning sphere of
hydrogen and helium, nor had we ever observed planet-sized objects such
as the Jovian satellites Ganymede and Callisto, which are half
water-ice. We had never been so close to a Moon-sized satellite such as
Io, which was known to be dispersing sodium throughout its Jovian
neighborhood and was thought to be generating a one-million-ampere
electrical current that in some way results in billions of watts of
radio emission from Jupiter.

The closer Voyager came to Jupiter the more apparent it became that the
scientific richness of the Jovian system was going to greatly exceed
even our most optimistic expectations. The growing realization among
Voyager scientists of the wealth of discovery is apparent in their
comments, discussions, and reports as recounted by the authors in their
descriptions of the two encounters.

Although many of the discoveries occurred in the few weeks around each
encounter, they were, of course, the result of more than those few weeks
of effort. In fact, planning started a decade earlier, and the Voyager
team of engineers and scientists had been designing, building, and
planning for the encounters for seven years. The Pioneer spacecraft made
the first reconnaissance of Jupiter in 1973-1974, providing key
scientific results on which Voyager could build, and discoveries from
continuing ground-based observations suggested specific Voyager studies.
Voyager is itself just the second phase of exploration of the Jovian
system. It will be followed by the Galileo program, which will directly
probe Jupiter’s atmosphere and provide long-term observations of the
Jovian system from an orbiting spacecraft. In the meantime, the Voyager
spacecraft will continue their journey to Saturn, and possibly Uranus
and Neptune, planets even more remote from Earth and about which we know
even less than we knew of Jupiter before 1979.

As is clearly illustrated in this recounting of the voyage to Jupiter,
scientific endeavors are human endeavors; just as Galileo could not have
foreseen the advancement in our knowledge initiated by his discoveries
of the four Jovian moons in 1610, neither can we fully comprehend the
scientific heritage that our exploration of space is providing future
generations.

  April 1980
                                                         Edward C. Stone
                                               Voyager Project Scientist




                            ACKNOWLEDGEMENT


The authors are grateful to the many members of the Voyager Project team
who not only made this historic mission of exploration possible but also
took time from their busy schedules to offer us assistance, information,
and encouragement in the preparation of this book.