Fifty years ago today — March 11, 1960 — the Pioneer-5 space probe launched from Cape Canaveral atop a Thor-Able rocket.
(Pioneer-5 with its solar power panels extended. NASA image from Wikimedia Commons.)
Pioneer-5 was one of the first deep space missions, and achieved a heliocentric (sun-centered) orbit between Earth and Venus. Scientists maintained contact with the vehicle for 106 days and received signals from a distance of 36.2 million kilometers (22.5 million miles), the farthest distance achieved at that time in the space race. Telemetry received from Pioneer-5 confirmed the existence of the interplanetary magnetic field, which until then had been just theoretical.
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