Luna 21 (Ye-8 series) was an uncrewed space mission, and its spacecraft, of the Luna program, also called Lunik 21, in 1973. The spacecraft landed on the Moon and deployed the second Soviet lunar rover, Lunokhod 2. The primary objectives of the mission were to collect images of the lunar surface, examine ambient light levels to determine the feasibility of astronomical observations from the Moon, perform laser ranging experiments from Earth, observe solar X-rays, measure local magnetic fields, and study mechanical properties of the lunar surface material. Luna 21 carried the second successful Soviet lunar rover, Lunokhod 2, and was launched less than a month after the last Apollo lunar landing.

Wikipedia: https://en.wikipedia.org/wiki/Luna_21. Original timeline Wikipedia link: https://en.wikipedia.org/wiki/Lunokhod_2. Related NASA reference: https://nssdc.gsfc.nasa.gov/planetary/chronology.html#1973. Description adapted from Wikipedia contributors (CC BY-SA 4.0; https://creativecommons.org/licenses/by-sa/4.0/).