Pioneer 10 was launched on March 3, 1972, at 01:49:00 UTC by the National Aeronautics and Space Administration from Space Launch Complex 36A in Florida, aboard an Atlas-Centaur. The third stage of the expendable vehicle consisted of a solid fuel Star-37E stage (TE-M-364-4) developed specifically for the Pioneer missions. This stage provided about 67 kilonewtons (15,000 lbf) of thrust and spun up the spacecraft. The spacecraft had an initial spin rate of 30 rpm. Twenty minutes following the launch, the vehicle’s three booms were extended, which slowed the rotation rate to 4.8 rpm. This rate was maintained throughout the voyage. The launch vehicle accelerated the probe for a net interval of 17 minutes, reaching a velocity of 51,682 km/h (32,114 mph). Pioneer 10 crossed the orbit of Saturn in 1976 and the orbit of Uranus in 1979. It crossed orbit of Pluto, still defined as a planet at the time (Pluto’s irregular orbit meant it was closer to the Sun than Neptune). On June 13, 1983, the craft crossed the orbit of Neptune, and so became the first human-made object to leave the proximity of the major planets of the Solar System. The mission came to an official end on March 31, 1997, when it had reached 67 AU (10.0 billion km; 6.2 billion mi) from the Sun, though the spacecraft was still able to transmit coherent data after this date. We celebrate this feat of engineering with a special letter issued by NASA …