Luna 22 was the second of two advanced lunar orbiters (the first being Luna 19) designed to conduct extensive scientific surveys from orbit. Launched about a year after termination of Lunokhod 2 operations on the lunar surface, Luna 22 performed a single midcourse correction en route the Moon May 30, 1974, before entering lunar orbit June 2, 1974. Initial orbital parameters were about 136 x 138 miles (219 × 222 kilometers) at 19 degrees 35 minutes inclination.
An orbital correction June 9, 1974, put the spacecraft in its nominal orbit of about 152 x 16 miles (244 × 25 kilometers) for its primary imaging mission. The spacecraft carried out four mapping sessions. A fifth one was canceled due to a significant decrease in the perilune from about 15 miles (24.5 kilometers) June 9 to about 9.5 miles (15.4 kilometers) June 12. Nevertheless, Luna 22 provided the best Soviet imagery of the Moon.
In addition to its primary mission of surface photography, Luna 22 also performed investigations to determine the chemical composition of the lunar surface, recorded meteoroid activity, searched for a lunar magnetic field, measured solar and cosmic radiation flux, and continued studies of the irregular magnetic field.
Through various orbital changes -- including a burn Nov. 11, 1974, to put the vehicle into a high 893 x 106-mile (1,437 × 171-kilometer) orbit to conduct gravitational experiments -- Luna 22 performed without any problems, continuing to return photos 15 months into the mission, although its primary mission ended by April 2, 1975.
The spacecraft’s maneuvering propellant was finally depleted on Sept. 2, 1974, and the highly successful mission was formally terminated in early November 1975. Luna 22 remains the final Soviet or Russian dedicated lunar orbiter.
- Credit: NASA