PIONEER SATURN ENCOUNTER [Illustration: NASA] CONTENTS Foreword 1 Introduction 3 Pioneer Saturn 4 Saturn Images 8 Science Highlights 21 Outward Bound 28 FOREWORD The Pioneer 10 and 11 spacecraft, launched in 1972 and 1973, respectively, were well named: they made the first crossings of the asteroid belt and were the first to encounter Jupiter and its intense radiation belts. Pioneer 11’s trajectory, bent into a hairpin curve by Jupiter’s powerful gravitational field, allowed it to recross the solar system to make the first flyby of Saturn almost a billion miles from Earth where it came within 13,300 miles of the cloud tops. Assembled in this publication is a selection of the pictures returned by Pioneer 11 of Saturn and its largest moon, Titan. These images are of great beauty as well as of great scientific interest, serving to whet our appetite for the more detailed observations to be made by Voyager in 1980 and 1981. Tracking of both Pioneers will continue for many more years, providing fundamental data on the nature of interplanetary space in the depths of the solar system. The results of these outer-planet Pioneer missions have far exceeded our hopes and expectations of a decade ago when the program was initiated. Robert A. Frosch, Administrator National Aeronautics and Space Administration September 1979 NASA National Aeronautics and Space Administration Ames Research Center Moffett Field. California 94035 [Illustration: Artist’s drawing of Saturn and its rings showing the Pioneer Saturn spacecraft passing under the rings and nearing closest approach to the planet. Actual pictures could not be obtained at this time because of the high speed of the spacecraft.] INTRODUCTION We have entered into a new era of space exploration. Missions undertaken during the lunar exploration of the 1960’s typically lasted a matter of days with commands issued and carried out in near real time. Now, a decade later, planetary voyages may last for many years as the spiraling trajectories of the spacecraft make periodic intersections with the orbits of the planets. Communicating with us across the vastness of space, these spacecraft report to us their experiences as they traverse the outer reaches of the solar system.