Margaret Hamilton’s software got man to the moon—but she didn’t stop there
It was on this day, July 20, in 1969, that the Apollo 11 astronauts reached the moon and Neil Armstrong took his famous small step. People celebrated the world over, though few were more relieved than Margaret Hamilton.
“I remember thinking, Oh my God, it worked,” the pioneering software engineer tells TIME. “I was so happy. But I was more happy about it working than about the fact that we landed.”
The “it” that worked was Apollo 11’s on-board flight software, which Hamilton, as part of the MIT team working with NASA, led the effort to build. There was no guarantee things would play out so smoothly. In fact, just before the lunar landing was supposed to happen, alarms went off indicating that there wasn’t enough room on the computer for the landing software to work effectively. Turns out a radar was sending unnecessary data to the computer, overloading it with superfluous information.
The work that Hamilton had done helped enable the computer to figure out which of the multiple processes it had to do was most important. “It got rid of the lesser priority jobs and kept the higher priority jobs, which included the landing functions,” she explains.
That fix gave NASA the confidence to go ahead with the historic moon landing.