Margaret Hamilton, the pioneering computer scientist whose software helped guide NASA’s Apollo missions, has died at 90. Hamilton died September 30, 2026, in Cambridge, Massachusetts, according to MIT News, leaving behind a legacy that reached far beyond the computers and code she once worked on at MIT’s Instrumentation Laboratory. She joined the Apollo project in 1965 and eventually led the team responsible for the onboard flight software used during crewed lunar missions. At a time when software engineering was still a new concept, Hamilton helped establish it as a discipline and became known for designing systems that anticipated human mistakes instead of assuming everything would go perfectly. That philosophy was shaped partly by an incident involving her daughter, Lauren, who accidentally triggered a simulator program and caused it to crash. Hamilton warned that a similar mistake could happen during an actual mission, and her concerns eventually proved valuable when a related problem occurred during Apollo 8.

Her most famous contribution came during Apollo 11 on July 20, 1969, when Neil Armstrong and Buzz Aldrin were preparing to land on the moon. The Apollo Guidance Computer began producing alarms as it became overloaded, creating a tense moment during the descent. Hamilton’s software had been designed to prioritize critical tasks and push less important processes aside, allowing the computer to continue providing essential information instead of shutting down. The landing proceeded, and Armstrong and Aldrin became the first humans to walk on the moon. Hamilton later received numerous honors, including the Presidential Medal of Freedom from President Barack Obama in 2016. A photograph of her standing beside a towering stack of Apollo code eventually made her famous to a wider audience. Yet her greatest legacy may be the lesson behind that image: historic achievements depend not only on the people in the spotlight, but also on the brilliant minds working quietly behind them.