Apollo 15 lunar surface exploration, August 1971. US astronaut David Scott at the Apollo Lunar Surface Experiments Package (ALSEP) site for Apollo 15. He is leaning to his right to handle a drill. The Solar Wind Spectrometer is in the foreground. The rack with drilling core equipment is to his left. The tape-like ribbons are cables that connect the central station to the individual ALSEP experiments. Scott used the drill to create a hole several metres deep for the placement of a probe to measure heat from the Moon's interior. Apollo 15 was the fourth manned mission to land on the Moon. The lunar lander 'Falcon' touched down in the Hadley region of the Moon on 30 July 1971. Astronauts David Scott and James Irwin spent a total of 18.5 hours outside their spacecraft, carrying out three exploration trips (EVAs) with the Lunar Roving Vehicle. Photographed by Irwin during the Apollo 15 second lunar surface extravehicular activity (EVA-2), on 1 August 1971.