Margaret Hamilton, the visionary computer scientist whose pioneering code guided NASA’s Apollo missions to the moon and established software engineering as a respected discipline, has passed at the age of 90.

Hamilton led the software engineering team at MIT’s Instrumentation Laboratory, which was tasked with writing the onboard flight code for NASA’s Apollo program. At a time when software development was still in its infancy and often viewed as an afterthought compared to hardware, she pioneered critical techniques in software reliability and system architecture. Hamilton notably coined the term "software engineering" to give the discipline equal standing alongside other engineering fields, laying the foundation that made human space exploration possible.

Her biggest contribution to spaceflight occurred during the Apollo 11 lunar landing in 1969. Moments before Neil Armstrong and Buzz Aldrin reached the moon’s surface, the lunar module's onboard computer triggered a 1202 alarm, meaning the system had overloaded due to a hardware switch malfunction. Thanks to the priority-driven software architecture Hamilton and her team had designed, the system automatically dropped low-priority background tasks to focus entirely on landing the spacecraft. Mission control trusted her software, allowing Apollo 11 to proceed safely and secure America's place in history.

Hamilton during her time as lead Apollo flight software designer - Image: NASA

Her approach to defensive programming was heavily influenced by real-world testing and a notorious incident involving her four-year-old daughter, Lauren. While playing in the flight simulator, her daughter accidentally triggered a pre-launch program during mid-flight simulation, crashing the system. Though NASA officials initially believed astronauts would never make such a mistake, Hamilton’s insistence on building safeguards proved vital during Apollo 8, when astronaut Jim Lovell accidentally triggered the exact same command. Her team quickly patched the navigational software, preventing potential disaster and establishing early standards for error-tolerant systems.

Hamilton’s extraordinary legacy extended far beyond NASA, too, spanning decades as a successful entrepreneur, CEO, and advocate for women in science, technology, engineering, and mathematics. She went on to found Higher Order Software and Hamilton Technologies, where she developed the Universal Systems Language to maximize software reliability and lower development costs. In 2016, President Obama awarded her the Presidential Medal of Freedom, and declared how "Hamilton defined new forms of software engineering and helped launch an industry that would forever change human history. Her software architecture led to giant leaps for humankind, writing the code that helped America set foot on the moon.”