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Pioneer 5 (also known as Pioneer P-2, and Able 4, and nicknamed the "Paddle-Wheel Satellite") was a spin-stabilized space probe in the NASA Pioneer program used to investigate interplanetary space between the orbits of Earth and Venus. It was launched on 11 March 1960 from Cape Canaveral Air Force Station Launch Complex 17A at 13:00:00 UTC with an on-orbit dry mass of . It was a diameter sphere with span across its four solar panels and achieved a solar orbit of 0.806 × 0.995 AU (121,000,000 by 149,000,000 km).