NASA brought the Mariner R-2 spacecraft out of storage and launched it just 36 days after the failure of Mariner 1. Mariner 2 was equipped with an identical complement of instrumentation as its predecessor (see Mariner 1).
The mission proved to be the first fully successful interplanetary mission performed by any nation. After a midcourse correction on Sept. 4, 1962, the spacecraft flew by Venus at a range of 21,657 miles (34,854 kilometers) at 19:59:28 UT on Dec. 14, 1962. During a 42 minute scan of the planet, Mariner 2 gathered significant data on the Venusian atmosphere and the surface before continuing on to heliocentric orbit. The radiometers, in particular, were able to conduct five scans of the night side of the planet, eight across the terminator, and five on the daylight side.
NASA maintained contact until 07:00 UT on Jan. 3, 1963 when the spacecraft was 53.9 million miles (86.7 million kilometers) from Earth, a new distance record for a deep space probe. The data returned implied that there was no significant difference in temperature across Venus. Readings from Mariner 2’s microwave radiometer indicated temperatures of 421 degrees Fahrenheit (216 degrees Celsius) on the dark side to 459 degrees Fahrenheit (237 degrees Celsius) on the day side.
Mariner 2 also found that there was a dense cloud layer that extended from 35 to 50 miles (56 to 80 kilometers) above the surface. The spacecraft detected no discernable planetary magnetic field, partly explained by the great distance between the spacecraft and the planet.
If in terms of scientific results Mariner 2 was only a modest success, it still retains the honor of being the very first successful planetary science mission in history.
NASA elected to stand down the third spacecraft in the series (Mariner R-3) scheduled for the 1964 launch period.
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.