Last week marked the 46th anniversary of the moon landing.

Stepping onto the lunar surface, Neil Armstrong famously declared that it was “one small step for man, one giant leap for mankind.” However, that step may never have happened without the efforts of Margaret Hamilton.

Director of the Software Engineering Division of the MIT Instrumentation Laboratory, Hamilton led the team responsible for developing Apollo’s on-board navigation and landing software. When a glitch in the system nearly aborted the mission three minutes prior to landing, it was Hamilton’s code that saved the day. As she explains,

Due to an error in the checklist manual, the rendezvous radar switch was placed in the wrong position. This caused it to send erroneous signals to the computer. The result was that the computer was being asked to perform all of its normal functions for landing while receiving an extra load of spurious data which used up 15% of its time. The computer (or rather the software in it) was smart enough to recognize that it was being asked to perform more tasks than it should be performing. It then sent out an alarm, which meant to the astronaut, I’m overloaded with more tasks than I should be doing at this time and I’m going to keep only the more important tasks; i.e., the ones needed for landing … Actually, the computer was programmed to do more than recognize error conditions. A complete set of recovery programs was incorporated into the software. The software’s action, in this case, was to eliminate lower priority tasks and re-establish the more important ones … If the computer hadn’t recognized this problem and taken recovery action, I doubt if Apollo 11 would have been the successful moon landing it was.

—Margaret Hamilton, Director of Apollo Flight Computer Programming MIT Draper Laboratory, Cambridge, Massachusetts, “Computer Got Loaded”, Letter to Datamation, March 1, 1971

When the Lunar lander successfully landed and Neil Armstrong took those historic steps, Margaret Hamilton was 32.

Since then, she has worked on 60 projects, published 130 papers, and founded and served as CEO of Hamilton Technologies. NASA has credited her with pioneering the development of ultra-reliable software and coining the term “software engineering” itself.

So, when R.E.M. sings “they put a man on the moon,” they are referring in large part to Margaret Hamilton.

Thank you, Margaret!

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