Pioneer 11 launched 1973

Pioneer 11, interplanetary probe, was launched by NASA April 6, 1973.  It studied the asteroid belt, Jupiter and Saturn.  Pioneer 11 passed through the asteroid belt in April 1974 and encountered Jupiter December 3, 1974.

It flew by Saturn September 1, 1979, becoming the first probe to encounter the planet. It passed beyond the orbit of the planets on February 23, 1990, making it the fourth man-made object to do so. The last meaningful data received was on November 24, 1995.  In 2002, its signal became too faint to detect.

Pioneer 10 launched 1972

Taking advantage of a rare alignment of the outer planets, NASA launched Pioneer 10 March 2, 1972.  NASA started preparing for the mission in 1964 and created two spacecraft, Pioneer F and Pioneer G.  Later they were renamed Pioneer 10 and Pioneer 11.

On November 8, 1973, Pioneer 10 crossed the orbit of Sinope, an outer moon of Jupiter and made its closest approach to the planet December 3.  The electron radiation around Jupiter caused false commands to be made but many were corrected by contingency commands.  An image of Io and some close-up pictures of Jupiter were lost but the spacecraft obtained pictures of Ganymede and Europa.

On its way out of the solar system, Pioneer 10 crossed the orbit of Saturn in 1976, the orbit of Uranus in 1979, and the orbit of Neptune in 1983.  It is the first spacecraft to leave the solar system.

The mission officially ended March 31, 1997 but the Deep Space Network kept track of its signal until January 23, 2003 when Pioneer 10 sent its last signal.

Pioneer 11 encounters Saturn 1979

Launched April 6, 1973, Pioneer 11 became the first space probe to encounter Saturn on September 1, 1979.  It followed Pioneer 10 through the asteroid belt and past Jupiter, but then headed toward Saturn.  During its flyby, it discovered a new ring and almost collided with a new moon discovered the day before, Epimetheus.  After the Voyager flybys, it was discovered that Janus (already known moon) and Epimetheus occupy the same orbit and are about the same size, so it could have been either one.

On September 29, 1995, NASA announced it was closing the project after over 22 years.