Today in History, June 13: Pioneer 10 Spacecraft

1983, on June 13, Pioneer 10, an American spacecraft, crossed the orbit of Neptune, the outermost planet, and became the first human-made object to leave the Solar System.

Pioneer 10, weighing 258 kilograms (569 pounds), was launched on March 2, 1972 from Cape Canaveral, Florida, USA, and had as first mission to explore Jupiter and its environment.

Between July 15, 1972, and February 15, 1973, it became the first spacecraft to traverse the asteroid belt of Jupiter. Photography of Jupiter began on November 6, 1973. At a range of 25,000,000 km (16,000,000 mi), a total of about 500 images were transmitted. The closest approach to the planet was on December 4, 1973, at a range of 132,252 km (82,178 mi). Part of the mission of the on-board instruments was to study the asteroid belt, the environment around Jupiter, the cosmic rays, and the solar wind.

On January 1, 1974, Pioneer 10 started its second, interstellar mission. In 1976 it crossed the orbit of Saturn, in 1979 the orbit of Uranus and in 1983 the orbit of Pluto. At that time Pluto was still defined as a planet.

On June 13, 1983, Pioneer 10 crossed the orbit of Neptune, the furthest planet away from the Sun and departed the Solar System.

Pioneer 10 was assembled around a hexagonal bus with a parabolic dish high-gain antenna of 2.74 m (9 ft.) diameter. The spacecraft was spin stabilized around the axis of the antenna. Its electric power was supplied by 4 radioisotope thermoelectric generators, fueled with plutonium-238, which provided a combined 155 W at launch. The spacecraft required 100 W only to power all systems! The data transmission rate at launch was 256 bit/s, with the rate degrading by about 1.27 millibit/s for each day during the mission. Its scientific instruments are protected by an aluminum honeycomb structure providing protection from meteoroids.

At the behest of Carl Sagan, an American astrophysicist, Pioneer 10 carries a 152 by 229 mm (6.0 by 9.0 in) gold-anodized aluminum plaque in case the spacecraft is ever found by intelligent life-forms from another planetary system. The plaque features the nude figures of a human male and female along with several symbols that are designed to provide information about the origin of the spacecraft.

The mission came to an official end on March 31, 1997, when it had reached a distance of 67 astronomical units (AU) (1 AU =‎149,597,870 km or 92,955,807 mi) from the Sun, though the spacecraft was still able to transmit coherent data after this date.

The last successful reception of telemetry was received from Pioneer 10 on April 27, 2002. Subsequent signals were barely strong enough to be detected, and provided no usable data. The final, very weak signal from Pioneer 10 was received on January 23, 2003 when it was 12 billion kilometers (80 AU) from the Earth. Further attempts to contact the spacecraft were unsuccessful. A final attempt was made on March 4, 2006. This was the last time the antenna of Pioneer 10 would be correctly aligned with the Earth. No response was received. NASA decided that it had probably fallen below the power threshold needed to operate the transmitter. Hence, no further attempts at contact were made.