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Forty four years ago today, Mariner 2 flew past Venus, becoming the first spacecraft from Earth to approach another planet. The unmanned probe flew 34,762 km miles above the surface of Venus, scanning the surface with radiometers and revealing an environment with cold clouds and a hot surface. During its 42-minute planetary scan, Mariner 2 also discovered Venus' high surface pressures, predominantly carbon dioxide atmosphere, and slow retrograde rotation rate. In addition, NASA learned that solar wind streams continuously in interplanetary space and that the density of cosmic dust near Venus is much lower than in the near-Earth region.
Mariner 2 was sent into space aboard an Atlas rocket on August 27, 1962 – just 36 days after Mariner 1 had failed approximately 5 minutes after liftoff. The probe's six-sided base housed all of the mission's electronics and provided a common point of assembly for a dish-shaped antenna and two rectangular solar panels. A tall pyramid-shaped mast atop Mariner 2 provided a platform for science experiments and brought the total height of the craft from 2 to 12 ft. Scientific instruments included a magnetometer, particle detectors, cosmic dust detector, radiometers, and radiometer reference horns. Except for the infrared and microwave radiometers, all of the scientific instruments were designed to operate throughout the entire mission. When electrical loads were heavy or rays from the sun were weak, Mariner 2 drew power from a 1000 Watt-hour silver-zinc battery.
NASA tracked Mariner 2's signal under January 3, 1963, when the spacecraft was 87.4 million kilometers from Earth. Today, the spacecraft remains trapped in an orbit around the Sun.
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