A last-moment sensor malfunction doomed this Soviet Moon landing attempt.
The first attempt to launch this vehicle took place at 07:05:36 UT on Sept. 4, 1965, but the launch was aborted due to a problem in a sensor that measured relative velocity on the rocket.
The subsequent launch a month later went off successfully and the Blok L upper stage sent Luna 7 on its way to the Moon. Unlike its predecessors, Luna 7 successfully carried out its mid-course correction on Oct. 5, 1965 on the way to the Moon in anticipation of a soft-landing two days later (at the time planned for 2208 UT on Oct. 7, 1965).
Unfortunately, immediately prior to a planned retro-fire during the approach to the lunar surface, the spacecraft suddenly lost attitude control and failed to regain it. One of its attitude control sensors — the one designed to lock onto Earth — stopped functioning, preventing it from reaching the desired orientation for firing its retro-engine.
Automatic programmed systems then prevented the main engine from firing. As controllers observed helplessly, Luna 7 plummeted to the lunar surface at a very high speed, crashing at 22:08:24 UT on Oct. 7, 1965 west of the Kepler crater, relatively near to the actual intended target.
Impact coordinates were 9 degrees north latitude and 49 degrees west latitude. Later investigation indicated that the optical sensor of the Yupiter-M astronavigation system had been set at the wrong angle and had lost sight of Earth during the critical attitude control maneuver. It was the tenth consecutive failure in the Ye-6 program.
Siddiqi, Asif A. Beyond Earth: A Chronicle of Deep Space Exploration, 1958-2016. NASA History Program Office, 2018.