Mission Summary
Pioneer P-31 was the third and final attempt of NASA’s Atlas-Able program to place a spacecraft in orbit around the Moon, and like the two before it, it was lost to a launch failure. Launched December 15, 1960, from Cape Canaveral, it carried the same paddle-wheel design and a science payload built to study the lunar environment from orbit.
The 176-kilogram probe was to settle into a lunar orbit of roughly 4,300 by 2,400 kilometers about 60 hours after launch, where its instruments would measure radiation near the Moon, count micrometeoroid impacts, and search for a lunar magnetic field. Its payload included a plasma probe designed by NASA’s Ames Research Center to sample the streams of charged particles around the Moon.
The flight lasted barely a minute. About 67 seconds after liftoff the Atlas-Able booster suffered a malfunction, and at 74 seconds it exploded roughly 12 kilometers above the ground. Investigators found that the Able upper stage had ignited prematurely while the first stage was still firing. With its loss, NASA closed out its 1959–1960 effort to reach lunar orbit, having failed all three times.
Sources and notes can be found on the Sources page.
