Mariner 2

Mariner 2 was the first successful spacecraft in the Mariner program, which began by sending spacecraft to Venus. The rocket carrying Mariner 1 went off-course during launch on July 22, 1962, and the spacecraft was destroyed. A month later, Mariner 2 was launched successfully on August 27, 1962, sending it on a 3½-month flight to Venus. On the way it measured for the first time the solar wind, a constant stream of charged particles flowing outward from the Sun. It also measured interplanetary dust, which turned out to be more scarce than predicted. In addition, Mariner 2 detected high-energy charged particles coming from the Sun, including several brief solar flares, as well as cosmic rays from outside the Solar system. As it flew by Venus on December 14, 1962, Mariner 2 scanned the planet with infrared and microwave radiometers, revealing that Venus has cool clouds and an extremely hot surface (because the bright, opaque clouds hide the planet's surface, Mariner 2 was not outfitted with a camera).