Lunar Orbiter to the Moon (1966 - 1967)
Five Lunar Orbiter missions were launched in 1966 through 1967 with the purpose of mapping the lunar surface before the Apollo landings. All five missions were successful, and 99% of the Moon was photographed with a resolution of 60 m or better.
nssdc.gsfc.nasa.gov/planetary/lunar/lunarorb.html