Thomas K. Mattingly, the astronaut who helped the crew of the Apollo 13 return to Earth after an oxygen tank exploded during their mission, has died at the age of 87, NASA announced on Thursday. “NASA astronaut TK Mattingly was key to the success of our Apollo Program, and his shining personality will ensure he is remembered throughout history,” said NASA Administrator Bill Nelson, referring to Mattingly as “one of our country’s heroes.” Mattingly was supposed to be on the Apollo 13 but was removed 72 hours before launch when he was exposed to rubella and was replaced by backup pilot Jack Swigert. He was also known as the command module pilot on the Apollo 16 mission that successfully landed on the moon in 1972. According to NASA’s statement, Mattingly joined the Air Force Aerospace Research Pilot School as a student before being recruited by NASA to be part of its 1966 astronaut program. Nelson said Mattingly had “unparalleled skill as a pilot” and “allowed for advancements in our learning beyond that of space.”