Galileo mission ends as probe crashes into Jupiter 2003

Galileo spacecraft, launched October 18, 1989, ended its mission when NASA sent it plunging into Jupiter's atmosphere, September 21, 2003.  It flew by Venus in February 1990 and flew by Earth in December 1990 and approached asteroid 951 Gaspra in October 1991.  It made a second flyby of Earth in December 1992 before making close observations of another asteroid Ida.  It discovered Ida's moon Dactyl, the first time a moon orbiting an asteroid had ever been seen.  

Galileo observed fragments of Comet Shoemaker-Levy 9 crash into Jupiter.  Besides examining Jupiter, it made several flybys of moons Europa and Io.  

NASA turned off Galileo's cameras in January 2002, since they had been permanently damaged by radiation.  They were able to recover scientific data from a damaged tape recorder and received measurements of the moon Amalthea, before taking its final plunge.

The mission was successful beyond imagination.

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.

Voyager 1 discovers volcanoes on Io, 1979

Voyager 1, launched September 5, 1977, discovered volcanoes on the Jovian moon Io March 8, 1979.  I remember it causing quite a stir back then because it was the first time active volcanoes had been observed anywhere other than Earth. 

On August 25, 2012, Voyager 1 became the first spacecraft (from Earth) to enter interstellar space and continues to send back information, although it takes almost a day for data to reach Earth.  Voyager 1 is expected to continue until about 2025, when it will not be able to supply enough power to operate any of its instruments.

http://www.todayinsci.com/3/3_08.htm
https://en.wikipedia.org/wiki/Voyager_1