Margaret Hamilton, who led the software engineering team for NASA’s Apollo program, died on Sep. 30. She was 90.

Hamilton oversaw development of the onboard flight software for the Apollo missions while working at MIT’s Instrumentation Lab. Her work established software engineering as a discipline focused on reliability and error prevention. She later founded two software companies and received numerous honors, including the 2016 Presidential Medal of Freedom.

Born in Paoli, Indiana, in 1936, Hamilton earned a mathematics degree from Earlham College in 1958. She moved to Boston in 1959 and began working at MIT’s meteorology department, where she collaborated with Edward N. Lorenz on weather prediction software. In 1961 she joined MIT Lincoln Laboratory and contributed to the SAGE air defense system.

In 1965 she was recruited by the Instrumentation Lab to develop software for NASA’s Apollo program. She became the first programmer on the project and later led the team responsible for the Command and Service Module software. During the Apollo 8 mission in 1968, a software error occurred when a pre-launch command was accidentally activated in flight. Hamilton’s team resolved the issue and later implemented defensive programming fixes that prevented similar failures.

For Apollo 11 in 1969, her software handled a critical 1202 error by prioritizing essential tasks and allowing the lunar landing to proceed. This demonstrated the effectiveness of priority-driven, fault-tolerant design.

Hamilton remained with the project through the 1970s. When the Instrumentation Lab became the independent Draper Laboratory, she continued to influence its work. She later founded Higher Order Software in 1976 and Hamilton Technologies in 1986, promoting error-prevention methodologies such as the Universal Systems Language.

Her contributions were recognized with awards including the NASA Exceptional Space Act Award (2003), the Computer History Museum Fellow Award (2017), and induction into the National Aviation Hall of Fame (2022). In 2015, the Apollo software she helped write was made publicly available on GitHub. A Lego Minifigure honoring her and other women of NASA history was released in 2017.

Hamilton is survived by her daughter Lauren, son-in-law Richard Selesnick, two grandsons, four great-grandchildren, and siblings John, David, and Kathryn. A memorial service is planned for spring in Cambridge, Massachusetts.

Olivier de Weck, Apollo Program Professor at MIT, described her career as a foundational example of systems engineering and leadership. He noted that her approach to handling the unknown remains influential across engineering disciplines.