Looking back at the Saturn system as it soared upward and outward, Voyager 1 continued its observations for nearly five weeks after closest Saturn approach. The spacecraft photographed the planet’s sunlit crescent, the ring shadows falling on the planet, and Saturn’s dark hemisphere illuminated by “ringshine.” It searched for lightning and auroras on the planet’s dark side and looked for “sun dogs” resulting from ammonia crystals in the atmosphere. It continued temperature and composition measurements and searched for new satellites out to the orbit of Mimas. It measured the flow of plasma in Saturn’s magnetosphere and now, its journey far from over, Voyager 1 proceeds toward the outer boundary of our solar system, as it seeks to probe the space among the stars of our galaxy, the Milky Way.] [Illustration: 11/16/80 5.3 million km (3.3 million mi) Departing Saturn, Voyager 1 photographed the planet from a unique perspective, clearly showing Saturn’s shadow on the rings.] [Illustration: 11/12/80 250,000 km (150,000 mi) During a 40-minute period on the day of encounter, the spacecraft was itself in the planet’s shadow. At this time, the wide-angle camera acquired a photograph of this shadow line, revealing ring material in a region very close to the planet, where no material had been previously observed. This inner ring, the D-Ring, is roughly 6000 kilometers (4000 miles) wide and extends to within about 6000 kilometers of Saturn’s cloudtops.] The Voyager Mission Only once every 175 years are the outer planets aligned in their orbits so that we can take advantage of gravity-assist trajectories to achieve encounters with Jupiter, Saturn, Uranus, and Neptune on one mission. The gravity-assist technique uses one planet’s gravity field and motion through space to alter the spacecraft’s flight path and propel it outward toward the next planet. Voyager 1’s trajectory, which was selected to best view Titan, has now propelled the spacecraft out of the ecliptic plane, while Voyager 2’s path will remain in this plane to provide future encounters with Uranus and possibly with Neptune. MISSION OBJECTIVES The Voyager Project was approved in June 1972 and had as its mission objectives: ★ Exploration of the Jupiter and Saturn planetary systems, including their atmospheres, rings, satellites, and magnetospheres ★ Comparative analyses of the two systems ★ Investigation of the interplanetary medium between Earth and Saturn A fourth objective, added in 1976, was to preserve the possibility of extending the mission to include an investigation of the planet Uranus and the interstellar medium. With the completion of Voyager 1’s Saturn flyby, it is now clear that these objectives will be achieved. SPACECRAFT CHARACTERISTICS