Luna 12 was launched to complete the mission that Luna 11 had failed to accomplish, i.e., to take high resolution photos of the Moon’s surface from lunar orbit.
The propulsion system, now called S5.5A, was redesigned to account for the failure of Luna 11 but otherwise was almost identical. Luna 12 successfully reached the Moon on Oct. 25, 1966 and entered a 64 x 1082-mile (103 × 1,742-kilometer) orbit.
About 2 hours later, the imaging system was turned on and worked for 64 minutes, returning 28 high resolution and 14 panoramic images. Film was developed, fixed, and dried automatically and scanned for transmission to Earth.
The Soviet press released the first photos taken of the surface on Oct. 29, 1966, pictures that showed the Sea of Rains and the Aristarchus crater. Resolution was as high as 49 to 66 feet (15 to 20 meters). No further photos were released at the time, although apparently 42 total images were obtained.
After completing its main imaging mission, Luna 12 was put into a spin-stabilized roll to carry out its scientific mission which was fulfilled quite successfully -- the only major failure was of the US-3 spectro-photometer.
Contact was finally lost on Jan. 19, 1967 after 302 communications sessions.
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.