when did the mission take place?
1971
Apollo 15
he 1971 mission began on July 26 and ended on August 7, with the lunar surface exploration taking place between July 30 and August 2. 
what is apollo 15? It was the ninth crewed mission in the United States' Apollo program and the fourth to land on the Moon.
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Apollo 15 [SEP] Introduction
Apollo 15 was the ninth crewed mission in the United States' Apollo program and the fourth to land on the Moon. It was the first J mission, with a longer stay on the Moon and a greater focus on science than earlier landings. Apollo 15 had the first use of the Lunar Roving Vehicle. The 1971 mission began on July 26 and ended on August 7, with the lunar surface exploration taking place between July 30 and August 2. Commander David Scott and Lunar Module Pilot James Irwin landed near Hadley Rille and explored the local area using the rover, allowing them to travel further from the lunar module than had been possible on previous missions.