Luna 6 was an attempted lunar soft landing mission. It was similar to the Luna 5 design, also carrying an imaging system and a radiation detector. It launched on 8 June 1965 at 7:41 UT. During the mid-course correction on 9 June the main retro-rocket failed to cut off as scheduled and fired until all of its propellant was exhausted, due to an erroneous ground command sent to the timer. This put the spacecraft on a trajectory to miss the Moon. The spacecraft was put through all the motions of an actual landing, jettisoning the lander and deploying the airbags, as an apparently successful practice run for the ground crew despite the fact that it flew by the Moon at a distance of 161,000 km on 11 June. Contact was lost at a distance of 600,000 km from Earth, the spacecraft presumably entering a heliocentric orbit.