Most famously, it was voyager 1 and 2 that explored these outer gas planets and have given us so much information. Other probes have been sent to these gas giants, but these are the the probes that visited all four gas giants between them.
The Pioneer 10 and Pioneer 11 probes flew past Jupiter before continuing their journey outward to deep space. The Voyager 1 and Voyager 2 probes also conducted flybys of Jupiter, Saturn, Uranus, and Neptune before heading towards interstellar space.
All four outer planets. Voyager 1 flew by Jupiter and Saturn only, and Voyager 2 flew by Jupiter, Saturn, Uranus, and Neptune. Pluto, which is no longer considered to be a planet, was not included in the fly-by.
These were two probes called voyager 1 and voyager 2. Voyager 1 visited Jupiter and Saturn, while voyager 2 visited all four gas giants; Jupiter, Saturn, Uranus, and Neptune. The probes also flew close to moons of these planets and discovered more moons in addition to many other things. Voyager 1 is now the most distant man made object from earth. Both are still able to send signals back to earth.
Jupiter (Voyager 1 & 2)Saturn (Voyager 1 & 2)Uranus (Voyager 2)Neptune (Voyager 2)See related link for a full description of the Voyager exploration
Nine probes have been sent to Jupiter to date. These include Pioneer 10 and 11, Voyager 1 and 2, Galileo, Cassini, New Horizons, Juno, and the most recent one being the European Space Agency's JUICE mission set to launch in 2022.
into deep space
Voyager 1 and 2
Voyager 1 and 2 visited the outer planets and went on into interstellar space.
The Pioneer 10 and Pioneer 11 probes flew past Jupiter before continuing their journey outward to deep space. The Voyager 1 and Voyager 2 probes also conducted flybys of Jupiter, Saturn, Uranus, and Neptune before heading towards interstellar space.
There have been 7 NASA space probes that flew by Jupiter: Pioneer 10 Pioneer 11 Voyager 1 Voyager 2 Ulysses Cassini New Horizons
Voyager 1 flew by Jupiter and Saturn. Voyager 2 flew by Jupiter, Saturn, Uranus, and Neptune.
Voyager I & II
Voyager did not discover any new planets. By the time Voyager was launched we already knew of all the planets in our solar system that we know of today. There were also two Voyager probes, not one. The first planet that either probe studied was Jupiter, which we had known for millennia. Voyager 1 flew by Jupiter in March 1979 while Voyager 2 flew by in July of the same year.
All four outer planets. Voyager 1 flew by Jupiter and Saturn only, and Voyager 2 flew by Jupiter, Saturn, Uranus, and Neptune. Pluto, which is no longer considered to be a planet, was not included in the fly-by.
These were two probes called voyager 1 and voyager 2. Voyager 1 visited Jupiter and Saturn, while voyager 2 visited all four gas giants; Jupiter, Saturn, Uranus, and Neptune. The probes also flew close to moons of these planets and discovered more moons in addition to many other things. Voyager 1 is now the most distant man made object from earth. Both are still able to send signals back to earth.
Voyager 2 flew by four planets; Jupiter, Saturn, Uranus and Neptune.
Jupiter (Voyager 1 & 2)Saturn (Voyager 1 & 2)Uranus (Voyager 2)Neptune (Voyager 2)See related link for a full description of the Voyager exploration