<P> The Voyager 1 probe was launched on September 5, 1977, from Launch Complex 41 at the Cape Canaveral Air Force Station, aboard a Titan IIIE launch vehicle . The Voyager 2 probe had been launched two weeks earlier, on August 20, 1977 . Despite being launched later, Voyager 1 reached both Jupiter and Saturn sooner, following a shorter trajectory . </P> <P> Voyager 1 began photographing Jupiter in January 1979 . Its closest approach to Jupiter was on March 5, 1979, at a distance of about 349,000 kilometers (217,000 miles) from the planet's center . Because of the greater photographic resolution allowed by a closer approach, most observations of the moons, rings, magnetic fields, and the radiation belt environment of the Jovian system were made during the 48 - hour period that bracketed the closest approach . Voyager 1 finished photographing the Jovian system in April 1979 . </P> <P> Discovery of active volcanic activity on the moon Io was probably the greatest surprise . It was the first time active volcanoes had been seen on another body in the Solar System . It appears that activity on Io affects the entire Jovian system . Io appears to be the primary source of matter that pervades the Jovian magnetosphere--the region of space that surrounds the planet influenced by the planet's strong magnetic field . Sulfur, oxygen, and sodium, apparently erupted by Io's volcanoes and sputtered off the surface by impact of high - energy particles, were detected at the outer edge of the magnetosphere of Jupiter . </P> <P> The two Voyager space probes made a number of important discoveries about Jupiter, its satellites, its radiation belts, and its never - before - seen planetary rings . </P>

Satellite is flying freely by end of may