Margaret Hamilton, who led MIT's Apollo flight software team, has died at 90

Margaret Hamilton, who led the MIT Instrumentation Laboratory team that wrote the onboard flight software for NASA's Apollo missions, died on 30 September 2026. She was 90. MIT announced her death on 7 October; NPR, reporting the next day, said the cause had not been given. A memorial service will be held in Cambridge, Massachusetts, in the spring, MIT said.

From weather prediction to Apollo

Hamilton was born in Paoli, Indiana, in 1936 and graduated from Earlham College in 1958 with a degree in mathematics and a minor in philosophy. She moved to Boston in 1959, when her husband began a law degree, and took a temporary job in MIT's meteorology department writing weather-prediction software for Edward Lorenz. In 1961 she joined MIT Lincoln Laboratory to program the XD-1, the prototype AN/FSQ-7 computer for the SAGE air-defence network. MIT dates her interest in software reliability to that work.

In 1965 she answered a newspaper advertisement from the Instrumentation Laboratory, which held NASA's contract for the Apollo onboard flight software. She was the first programmer the lab hired for the project and its first woman programmer, according to MIT. She worked first on the uncrewed flights and then led the team writing software for the crewed missions, and by 1968 she was assistant director in charge of the Command and Service Module team. MIT puts the number of people then working on Apollo software at more than 400; NPR describes the group she led as more than 100 engineers.

The programs were stored in the guidance computer by weaving copper wire through magnetic cores by hand. NPR reports that overseeing that process earned her the nickname "rope mother" in the lab.

Designing for the operator's mistake

MIT's account of her Apollo work turns on two episodes. Her daughter Lauren, then four, crashed the command module simulator by starting P01, a pre-launch program, while the simulated spacecraft was in flight. Hamilton proposed a software guard against it and was overruled on the grounds that trained astronauts would not make that mistake. During Apollo 8 in 1968, Jim Lovell selected P01 in flight and erased the navigation data. Her team was called in to recover, and her changes went into the program afterwards. The second came moments before the Apollo 11 landing in July 1969, when the guidance computer raised a 1202 alarm because it was overloaded. The software had been built to schedule work by priority, so it dropped lower-priority background tasks and kept the landing running. Controllers in Houston trusted it and let the descent continue.

The name of the discipline

Hamilton spent much of her later career arguing that the work deserved the standing of engineering. She told the Spanish newspaper El Pais that she "began to use the term 'software engineering' to distinguish it from hardware and other kinds of engineering", and that when she first used the phrase, "it was considered to be quite amusing." NPR reports that she is credited with coining it.

She stayed at the Instrumentation Laboratory into the 1970s, as it left MIT to become the independent Draper Laboratory; a 2016 MIT News report dates the spin-off to 1973. In 1976 she founded Higher Order Software, built on her approach of error prevention and fault tolerance. A decade later she founded Hamilton Technologies, whose main product is the Universal Systems Language, a language and method for modelling complex systems. MIT counts more than 130 publications under her name.

Recognition

President Barack Obama presented her with the Presidential Medal of Freedom at the White House on 22 November 2016, in a year when the late Grace Hopper was also honoured. The citation said Hamilton "defined new forms of software engineering and helped launch an industry that would forever change human history." She received NASA's Exceptional Space Act Award in 2003 and the Computer History Museum's Fellow Award in 2017. In 2015 the Apollo software she helped to develop was posted in its entirety on GitHub.

She is survived by her daughter, Lauren Hamilton; her son-in-law, Richard Selesnick; two grandsons; four great-grandchildren; and her siblings John, David and Kathryn.