Apollo 15 15 separated from the booster, the S-IVB maneuvered away, and would impact the Moon about an hour after the crewed spacecraft entered lunar orbit, though due to an error the impact was away from the intended target. The booster's impact was detected by the seismometers left on the Moon by Apollo 12 and Apollo 14, providing useful scientific data. There was a malfunctioning light on the craft's service propulsion system (SPS); after considerable troubleshooting, the astronauts did a test burn of the system that also served as a midcourse correction. This occurred about 028:40:00 into the mission. Fearing that the
Lander (spacecraft) Surveyor. The U.S. manned Apollo Lunar Modules (since 1969) with rovers (since 1971) and Soviet unmanned late big landers (since 1969), Lunokhods (since 1970) and sample return missions (since 1970) used a rocket descent engine for a soft landing of astronauts and lunar rovers on the Moon. The Altair spacecraft, previously known as the "Lunar Surface Access Module" or "LSAM", was the planned lander for the Constellation program, prior to the cancellation of Project Constellation. Russia has plans for Luna-Grunt mission to return samples from the Moon by 2021. The Chinese Chang'e 3 mission and its Jade Rabbit rover landed