Apollo 9 launched 50 years ago, on March 3, 1969, and it might be the most important but least celebrated of the early Apollo missions. In fact, it was so important to NASA’s ultimate lunar landing goal that the space agency had a series of contingency missions in place to ensure it could get as much data as possible if something went wrong.

Apollo 9’s mission wasn’t necessarily glamorous. Commander Jim McDivitt, Command Module Pilot (CMP) Dave Scott, and Lunar Module Pilot (LMP) Rust