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Margaret Hamilton, who coined the term "software engineering" and led flight software development for NASA’s Apollo program in the 1960s, died last week at age 90. Olivier de Weck, interim head of the MIT Department of Aeronautics and Astronautics, called her a pioneer ahead of her time who developed advanced code to help create one of humanity’s most complex systems. Born in 1936 in Paoli, Indiana, Hamilton graduated from Earlham College in 1958 with a mathematics degree and a minor in philosophy. She later worked for MIT mathematician Edward Lorenz, teaching herself programming when computers were still a novelty.

Hamilton moved to the SAGE project at MIT in 1961, where she deciphered a program written in Latin and Greek. In 1965, she was hired by NASA’s Instrumentation Lab as the first programmer for the Apollo program, working on six lunar landing missions from 1969 to 1972. She trained her replacement, Ellen Fetter, after moving projects in 1961. Her team included New England textile workers who manually wove binary code onto copper wire cores, earning Hamilton the nickname "rope mother."

Hamilton faced a significant challenge when her four-year-old daughter, Lauren, accidentally typed "P01" into the system during a simulation, causing it to crash. This incident, which also occurred on the Apollo 8 mission under astronaut Jim Lovell, led Hamilton to propose a safeguard against such errors. Her idea resulted in a fail-safe that prioritized essential tasks when the onboard guidance computer became overloaded. During the historic Apollo 11 landing in 1969, this system prevented an abort by canceling nonessential alarms while keeping critical data visible, ensuring the Eagle lunar module safely landed on the Sea of Tranquility.

The software Hamilton helped develop was added to GitHub in 2015. In 2019, Google honored her contribution by training solar mirrors at its Mojave Desert farm to create a portrait of Hamilton in reflected moonlight. After leaving NASA, she founded Higher Order Software and later Hamilton Technologies, focusing on error prevention and defensive programming. She is survived by her daughter Lauren, son-in-law Richard Selesnick, two grandsons, four great-grandchildren, and three siblings.