Six Apollo missions put astronauts on the Moon. Each flight carried three men. Two of them landed, while the third stayed aboard the command module in lunar orbit. On the surface, astronauts gathered rocks, took pictures, and set up experiments. But the guys they left behind could be just as busy. Consider Ken Mattingly, the command module pilot for Apollo 16, which arrived at the Moon 50 years ago today. Mattingly stayed in orbit, about 70 miles up, while crewmates John Young and Charles Duke spent three days on the surface. Mattingly operated a suite of scientific instruments. The gear included cameras, which mapped about six percent of the Moon in high resolution. It also included instruments that mapped the mineral and chemical composition of the ground below, probed for magnetic fields, and looked for traces of an atmosphere. Mattingly also used binoculars to help make his own observations of the Moon. After Young and Duke rejoined him, they dropped a small satellite into lunar or
