6 April 1973

The Pioneer 11 spacecraft is launched.

Pioneer 11 also known as Pioneer G is a 259-kilogram robotic space probe launched by NASA on April 6, 1973 to study the asteroid belt, the environment around Jupiter and Saturn, solar wind and cosmic rays. It was the first probe to encounter Saturn and the second to fly through the asteroid belt and by Jupiter. Thereafter, Pioneer 11 became the second of five artificial objects to achieve the escape velocity that will allow them to leave the Solar System. Due to power constraints and the vast distance to the probe, the last routine contact with the spacecraft was on September 30, 1995, and the last good engineering data was received on November 24, 1995.

The Pioneer 11 probe was launched on April 6, 1973 at 02:11:00 UTC, by the National Aeronautics and Space Administration from Space Launch Complex 36A at Cape Canaveral, Florida aboard an Atlas-Centaur launch vehicle. Its twin probe, Pioneer 10, had launched a year earlier on March 3, 1972. Pioneer 11 was launched on a trajectory directly aimed at Jupiter without any prior gravitational assists. In May 1974, Pioneer was retargeted to fly past Jupiter on a north-south trajectory enabling a Saturn flyby in 1979. The maneuver used 17 pounds of propellant, lasted 42 minutes and 36 seconds and increased Pioneer 11’s speed by 230 km/h. It also made two mid-course corrections, on April 11, 1973 and November 7, 1974.