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.