Pioneer 10

Pioneer 10, initially designated Pioneer F, was NASA's first mission to the outer planets. It launched from Cape Canaveral on 2 March 1972, on a mission designed chiefly for a Jupiter flyby. NASA reports that it was the first spacecraft to travel beyond Mars and the first to pass through the main asteroid belt. The spacecraft used radioisotope thermoelectric generators for electrical power.

Pioneer 10 passed Jupiter in December 1973, becoming the first spacecraft to make a close reconnaissance of the planet. NASA records its closest approach on 4 December, at about 130,354 kilometres from Jupiter. The spacecraft imaged the planet and several of its moons and measured the planet's atmosphere, magnetic field, magnetosphere and radiation environment. These observations supplied important information for planning later outer-planet missions.

After the encounter, Pioneer 10 continued outward. NASA records it crossing Saturn's orbital distance in 1976 and Neptune's orbit in 1983. Routine contact ended in 1997, but the spacecraft was tracked intermittently afterward. Its last faint signal reached Earth on 23 January 2003; declining power meant the radio transmitter could no longer be heard. A final attempt to detect a signal in 2006 was unsuccessful.

Pioneer 10 carried a gold-anodized metal plaque, also carried by Pioneer 11, intended as a pictorial message should another spacefaring civilization ever find a spacecraft. NASA describes the plaque as identifying the spacecraft's time and place of origin; its diagrams show a man and woman and Earth's location in the Galaxy. This was a symbolic message, not a functioning communication device.