After approval by NASA Headquarters in September 1961, JPL prepared three spacecraft based on the design of the Ranger Block I series (therefore named Mariner R) to fly by Venus in late 1962. Each spacecraft carried a modest suite (9 kilograms) of scientific instrumentation but had no imaging capability. The spacecraft included 54,000 components and was designed to maintain contact with Earth for 2,500 hours -- an ambitious goal given that the (still unsuccessful) Ranger was designed for only 65 hours of contact. Mariner 1 would have flown by Venus at a range of 29,000 kilometers on 8 December 1962, but due to an incorrect trajectory during launch, range safety had to destroy the booster and its payload at T+290 seconds.
