The Pioneer program was an attempt by N.A.S.A. to explore the planets. The most famous of these missions were Pioneer 10 and 11 whose voyages took them out to the furthest reaches of the solar system. The program is now defunct, it was overtaken by the Voyager project which gains more attention. Some of the earlier attempts were failures but where you fail, you learn from the past mistakes and ensure you don't make them again.
The more famous of the two deep space planetary probes, it was launched on 3rd March, 1973. It was also referred to as Pioneer F. It became the first space probe to travel further than the Asteroid Belt between Mars and Jupiter. The project lasted for just days short of 30 years when contact was lost with probe. At the time of its loss, it had travelled a distance equal to 80 times the distance of Earth and the Sun. It broke records such as the first probe to visit Jupiter and the first to pass out of the heliosphere, the point at which the Sun's radiation meets with interstellar radiation. As the energy source has now been depleted, it is just coasting along in space and in 30,000 years will pass within 3 light years of Ross 248, a star in the Taurus constellation. The Voyager 1 probe is travelling at a faster rate than Pioneer and has over taken it. 1
Pioneer 11 was launched on 5th April 1973 on a different course but still ultimately on its way out of the solar system. It made the first direct observations of Saturn. Its mission stopped on 30th September 1995 when the last signal was received. The reason for loss was the view of the antenna of the the space probe. The probe is heading towards the constellation of Aquila.
On board both of the Pioneers is a plaque that should intelligent alien life forms out there ever come across it will be able to decipher it. The plaque was designed by Carl Sagan and Frank Drake, two well respected American astronomers at the time. Frank Drake came up with the drake equation. Carl Sagan created SETI (Search for ExtraTerrestrial Intelligence Instituition). The plaque shows a naked man and woman and where in the Solar System that they can find our home planet. The hand raised by the man is supposed to show that we are a friendly race on the planet. The plaques are gold-anodized aluminum so as to withstand the environment it finds itself in.