The American Pioneer program of unmanned space missions was designed for planetary exploration. There were a number of such missions in the program, but the most notable were Pioneer 10 and Pioneer 11, which explored the outer planets and left the solar system. Both carry a golden plaque (see Pioneer plaque), depicting a man and a woman and information about the origin and the creators of the probes, should any extraterrestrials find them someday.
- Pioneer 0 - Lunar orbiter, destroyed in launcher failure
- Pioneer 1 - Lunar orbiter, missed Moon due to launcher failure
- Pioneer 2 - Lunar orbiter, destroyed in launcher failure
- Pioneer 3 - Lunar flyby, missed Moon due to launcher failure
- Pioneer 4 - Lunar flyby, achieved Earth escape velocity
- Pioneer 5 - interplanetary space between Earth and Venus
- Pioneer 6 - interplanetary space "weather network"
- Pioneer 7 - interplanetary space "weather network"
- Pioneer 8 - interplanetary space "weather network"
- Pioneer 9 - interplanetary space "weather network"
- Pioneer 10 - Jupiter, interstellar space
- Pioneer 11 - Jupiter, Saturn, interstellar space