Margaret Hamilton: The Woman behind the Software for the Apollo 11 Moon Mission
It was thanks to her engineering and programming expertise that Apollo 11 was able to land on the moon.
Curated/Reviewed by Matthew A. McIntosh
Margaret Heafield Hamilton (born August 17, 1936) is an American computer scientist, systems engineer, and business owner. She was director of the Software Engineering Division of the MIT Instrumentation Laboratory, which developed on-board flight software for NASA’s Apollo program. She later founded two software companies—Higher Order Software in 1976 and Hamilton Technologies in 1986, both in Cambridge, Massachusetts.
Hamilton has published more than 130 papers, proceedings, and reports, about sixty projects, and six major programs. She is one of the people credited with coining the term “software engineering”.
On November 22, 2016, Hamilton received the Presidential Medal of Freedom from president Barack Obama for her work leading to the development of on-board flight software for NASA’s Apollo Moon missions.
Early Life and Education
Margaret Elaine Heafield was born August 17, 1936, in Paoli, Indiana, to Kenneth Heafield and Ruth Esther Heafield (née Partington). The family later moved to Michigan, where Margaret graduated from Hancock High School in 1954. She studied mathematics at the University of Michigan in 1955 before transferring to Earlham College, where her mother was a student; she earned a BA in mathematics with a minor in philosophy in 1958. She cites Florence Long, the head of the math department at Earlham, as helping with her desire to pursue abstract mathematics and become a mathematics professor. She says her poet father and headmaster grandfather inspired her to include a minor in philosophy in her studies.
In Boston, Hamilton initially intended to enroll in graduate study in abstract mathematics at Brandeis. However, in mid-1959, Hamilton began working for Edward Norton Lorenz, in the meteorology department at MIT. She developed software for predicting weather, programming on the LGP-30 and the PDP-1 computers at Marvin Minsky’s Project MAC. Her work contributed to Lorenz’s publications on chaos theory. At the time, computer science and software engineering were not yet established disciplines; instead, programmers learned on the job with hands-on experience. She moved on to another project in the summer of 1961, and hired and trained Ellen Fetter as her replacement.
From 1961 to 1963, Hamilton worked on the Semi-Automatic Ground Environment (SAGE) Project at the MIT Lincoln Lab, where she was one of the programmers who wrote software for the prototype AN/FSQ-7 computer (the XD-1), used by the U.S. Air Force to search for possibly unfriendly aircraft. She also wrote software for a satellite tracking project at the Air Force Cambridge Research Laboratories. The SAGE Project was an extension of Project Whirlwind, started by MIT to create a computer system that could predict weather systems and track their movements using simulators. SAGE was soon developed for military use in anti-aircraft air defense. Hamilton said:
What they used to do when you came into this organization as a beginner, was to assign you this program which nobody was able to ever figure out or get to run. When I was the beginner they gave it to me as well. And what had happened was it was tricky programming, and the person who wrote it took delight in the fact that all of his comments were in Greek and Latin. So I was assigned this program and I actually got it to work. It even printed out its answers in Latin and Greek. I was the first one to get it to work.
It was her efforts on this project that made her a candidate for the position at NASA as the lead developer for Apollo flight software.
Hamilton then joined the Charles Stark Draper Laboratory at MIT, which worked on the Apollo Space Mission. Hamilton was initially hired as a programmer for this process but moved on into system designs. By 1965, she was in charge of all Command Module software, which was all the software for navigation and lunar landing guidance. Hamilton’s team was responsible for developing in-flight software, which included algorithms designed by various senior scientists for the Apollo command module, Apollo lunar module, and the subsequent Skylab. Another part of her team designed and developed the systems software. This included error detection and recovery software such as restarts and the Display Interface Routines (also known as the Priority Displays), which Hamilton designed and developed. She worked to gain hands-on experience during a time when computer science courses were uncommon and software engineering courses did not exist. Hamilton also served as Director of the Software Engineering Division.
Her areas of expertise include: systems design and software development, enterprise and process modeling, development paradigm, formal systems modeling languages, system-oriented objects for systems modeling and development, automated life-cycle environments, methods for maximizing software reliability and reuse, domain analysis, correctness by built-in language properties, open-architecture techniques for robust systems, full life-cycle automation, quality assurance, seamless integration, error detection and recovery techniques, human-machine interface systems, operating systems, end-to-end testing techniques, and life-cycle management techniques. These made her code incredibly reliable because they helped programmers identify and fix anomalies before they became major problems.
In one of the critical moments of the Apollo 11 mission, the Apollo Guidance Computer, together with the on-board flight software, averted an abort of the landing on the Moon. Three minutes before the lunar lander reached the Moon’s surface, several computer alarms were triggered. The on-board flight software captured these alarms with the “never supposed to happen displays” interrupting the astronauts with priority alarm displays. Hamilton had prepared for just this situation years before:
There was one other failsafe that Hamilton likes to remember. Her “priority display” innovation had created a knock-on risk that astronaut and computer would slip out of synch just when it mattered most. As the alarms went off and priority displays replaced normal ones, the actual switchover to new programmes behind the screens was happening “a step slower” than it would today.
Hamilton had thought long and hard about this. It meant that if Aldrin, say, hit a button on the priority display too quickly, he might still get a “normal” response. Her solution: when you see a priority display, first count to five.
By some accounts, the astronauts had inadvertently left the rendezvous radar switch on, causing these alarms to be triggered (the claim that the radar was left on inadvertently by the astronauts is disputed by Robert Wills with the National Museum of Computing). The computer was overloaded with interrupts caused by incorrectly phased power supplied to the lander’s rendezvous radar. The program alarms indicated “executive overflows”, meaning the guidance computer could not complete all of its tasks in real time and had to postpone some of them. The asynchronous executive designed by J. Halcombe Laning was used by Hamilton’s team to develop asynchronous flight software:
Because of the flight software’s system-software’s error detection and recovery techniques that included its system-wide “kill and recompute” from a “safe place” restart approach to its snapshot and rollback techniques, the Display Interface Routines (AKA the priority displays) together with its man-in-the-loop capabilities were able to be created in order to have the capability to interrupt the astronauts’ normal mission displays with priority displays of critical alarms in case of an emergency. This depended on our assigning a unique priority to every process in the software in order to ensure that all of its events would take place in the correct order and at the right time relative to everything else that was going on.
Hamilton’s priority alarm displays interrupted the astronauts’ normal displays to warn them that there was an emergency “giving the astronauts a go/no go decision (to land or not to land)”. Jack Garman, a NASA computer engineer in mission control, recognized the meaning of the errors that were presented to the astronauts by the priority displays and shouted, “Go, go!” and they continued. Paul Curto, senior technologist who nominated Hamilton for a NASA Space Act Award, called Hamilton’s work “the foundation for ultra-reliable software design”.
Hamilton later wrote of the incident:
The computer (or rather the software in it) was smart enough to recognize that it was being asked to perform more tasks than it should be performing. It then sent out an alarm, which meant to the astronaut, ‘I’m overloaded with more tasks than I should be doing at this time and I’m going to keep only the more important tasks’; i.e., the ones needed for landing … Actually, the computer was programmed to do more than recognize error conditions. A complete set of recovery programs was incorporated into the software. The software’s action, in this case, was to eliminate lower priority tasks and re-establish the more important ones … If the computer hadn’t recognized this problem and taken recovery action, I doubt if Apollo 11 would have been the successful moon landing it was.Letter from Margaret H. Hamilton, Director of Apollo Flight Computer Programming MIT Draper Laboratory, Cambridge, Massachusetts, titled “Computer Got Loaded”, published in Datamation, March 1, 1971
In 1976, Hamilton co-founded with Saydean Zeldin a company called Higher Order Software (HOS) to further develop ideas about error prevention and fault tolerance emerging from their experience at MIT working on the Apollo program. They created a product called USE.IT, based on the HOS methodology they developed at MIT. It was successfully used in numerous government programs including a project to formalize and implement C-IDEF, an automated version of IDEF, a modeling language developed by the U.S. Air Force in the Integrated Computer-Aided Manufacturing (ICAM) project. In 1980, British-Israeli computer scientist David Harel published a proposal for a structured programming language derived from HOS from the viewpoint of and/or subgoals. Others have used HOS to formalize the semantics of linguistic quantifiers, and to formalize the design of reliable real-time embedded systems.
Hamilton was the CEO of HOS through 1984 and left the company in 1985. In March 1986, she founded Hamilton Technologies, Inc. in Cambridge, Massachusetts. The company was developed around the Universal Systems Language (USL) and its associated automated environment, the 001 Tool Suite, based on her paradigm of development before the fact for systems design and software development.
Anthony Oettinger, Barry Boehm, and Hamilton have been credited with naming the discipline of “software engineering”. Hamilton details how she came to make up the term “software engineering”:
When I first came up with the term, no one had heard of it before, at least in our world. It was an ongoing joke for a long time. They liked to kid me about my radical ideas. It was a memorable day when one of the most respected hardware gurus explained to everyone in a meeting that he agreed with me that the process of building software should also be considered an engineering discipline, just like with hardware. Not because of his acceptance of the new ‘term’ per se, but because we had earned his and the acceptance of the others in the room as being in an engineering field in its own right.
When Hamilton started using the term “software engineering” during the early Apollo missions, software development was not taken seriously compared to other engineering, nor was it regarded as a science. Hamilton was concerned with legitimizing software development as an engineering discipline. Over time the term “software engineering” gained the same respect as any other technical discipline. The IEEE Software September/October 2018 issue celebrates the 50th anniversary of software engineering. Hamilton talks about “Errors” and how they influenced her work related to software engineering and how her language, USL, could be used to prevent the majority of “Errors” in a system. Writing in Wired, Robert McMillan noted: “At MIT she assisted in the creation of the core principles in computer programming as she worked with her colleagues in writing code for the world’s first portable computer”. Hamilton’s innovations go beyond the feats of playing an important role in getting humans to the Moon. According to Wired‘s Karen Tegan Padir: “She, along with that other early programming pioneer, COBOL inventor Grace Hopper, also deserve tremendous credit for helping to open the door for more women to enter and succeed in STEM fields like software.”
In 2019, to celebrate 50 years to the Apollo landing, Google decided to make a tribute to Hamilton. The mirrors at the Ivanpah plant were configured to create a picture of Hamilton and the Apollo 11 by moonlight.
- “The NASA Heritage Of Creativity” (PDF). 2003 Annual Report of the NASA Inventions & Contributions Board. NASA.
- “President Obama Names Recipients of the Presidential Medal of Freedom”. whitehouse.gov. November 16, 2016. Retrieved July 26, 2022.
- Spicer, Dan (April 27, 2017). “2017 CHM Fellow Margaret Hamilton”. Computer History Museum.
- Welch, Rosanne; Lamphier, Peg A., eds. (February 28, 2019). Technical Innovation in American History: An Encyclopedia of Science and Technology. Vol. 3. ABC-CLIO. p. 62.
- “Ruth Esther Heafield”. Wujek-Calcaterra & Sons – Tributes.com.
- “Commings, Goings and Events”. The Evening News. Sault Ste Marie, Michigan. December 10, 1952.
- “Pioneers in Computer Science”. Utah State University.
- “Former Earlham Student Had Role in Moon Flight”. Palladium-Item. Richmond, Indiana. August 15, 1969 – via Newspapers.com.
- “2009 Outstanding Alumni and Distinguished Service Awards”. Earlham College.
- “The Woman Who Taught Me – Margaret Hamilton MAKERS Moment”. Makers.com.
- “Margaret Hamilton: The Untold Story of the Woman Who Took Us to the Moon”. Futurism. July 20, 2016.
- Sokol, Joshua (May 20, 2019). “The Hidden Heroines of Chaos”. Quanta Magazine. Retrieved May 25, 2019.
- Lorenz, Edward (March 1962). “The statistical prediction of solutions of dynamic equations” (PDF). Proceedings of the International Symposium on Numerical Weather Prediction in Tokyo, November 7–13, 1960. The Meteorological Society of Japan: 629–635.
- Wayne, Tiffany K. (2011). American Women of Science Since 1900. ABC-CLIO. pp. 480–82.
- Levy, Steven (1984). Hackers: Heroes of the Computer Revolution. Doubleday. pp. Chapter 5:The Midnight Computer Wiring Society.
- “About Margaret Hamilton”. klabs.org.
- “AGC – Conference 1: Margaret Hamilton’s introduction”. authors.library.caltech.edu.
- Weinstock, Maia (August 17, 2016). “Scene at MIT: Margaret Hamilton’s Apollo code”. MIT News.
- Rayl, A.J.S (October 16, 2006). “NASA Engineers and Scientists-Transforming Dreams Into Reality”. 50th Magazine. NASA.
- “AGC Biography – Margaret Hamilton”. authors.library.caltech.edu. The Dibner Institute for the History of Science and Technology. May 9, 2002.
- “NASA Engineers and Scientists-Transforming Dreams Into Reality”. NASA.
- Hoag, David (September 1976). The History of Apollo On-board Guidance, Navigation, and Control (PDF) (Report). Charles Stark Draper Laboratory.
- Michael Braukus NASA News “NASA Honors Apollo Engineer”
- Green, Alan (June 1967). Keyboard and Display Program and Operation (PDF) (Report). Charles Stark Draper Laboratory. p. 29.
- “Margaret Hamilton 2017 Fellow”. Computer History Museum.
- “The NASA Heritage of Creativity.” 2003 Annual Report of the NASA Inventions and Contributions Board, 2003.
- “Moon landing memories:’Apollo 11 changed civilisation and I had a part in it'”. The Times of London. July 15, 2019.
- Whittell, Giles (July 13, 2004). “First Woman”. Tortoise Media.
- Wills, Robert (October 26, 2019). “Light-years ahead”.
- Eyles, Don. “Tales from the Lunar Module Guidance Computer”. 27th Annual Guidance and Control Conference of the American Astronautical Society.
- Blair-Smith, Hugh (November 7, 2011). “System integration issues in Apollo 11”. IEEE Aerospace and Electronic Systems Magazine. 26 (11): 16–24.
- Hamilton, Margaret; Hackler, William (December 12, 2008). “Universal Systems Language: Lessons Learned from Apollo”. IEEE Computer. 41 (12): 34–43.
- Collins, Michael; Aldrin, Edwin E., Jr. (1975). “A Yellow Caution Light”. In Cortright, Edgar M (ed.). Apollo Expeditions to the Moon. Washington, D.C.: NASA.
- Hayes, Brian (May–June 2019). “Moonshot Computing”. American Scientist.
- Mindell, David A. (2011). Digital Apollo. MIT Press. p. 149.
- Snyder, Lawrence and Henry, Ray Laura, “Fluency7 with Information Technology”, Pearson
- Hamilton, Margaret (July 17, 2009). “Recalling the ‘Giant Leap'”. MIT News.
- Lickly, Dan (July 17, 2009). “Recalling the ‘Giant Leap'”. MIT News.
- Hamilton, Margaret H. (March 1, 1971). “Computer Got Loaded, letter to the editor of Datamation”. Datamation (Letter).
- Roberts, Edward B. (1991). Entrepreneurs in High Technology: Lessons from MIT and Beyond. Oxford University Press. pp. 41.
- Huber, Hartmut (August 1987). Higher Order Software – Evaluation and Critique (PDF) (Report). Naval Surface Warfare Center. pp. 2–1.
- M. Hamilton, S. Zeldin (1976) “Higher order software—A methodology for defining software” IEEE Transactions on Software Engineering, vol. SE-2, no. 1, Mar. 1976.
- Thompson, Arthur A.; Strickland, A. J., (1996), “Strategic Management: Concepts and Cases”, McGraw-Hill Companies
- Rowena Barrett (June 1, 2004). Management, Labour Process and Software Development: Reality Bites. Routledge. p. 42.
- Hamilton, Margaret; Zeldin, Saydean (1974). Robinet, B. (ed.). “Higher order software techniques applied to a space shuttle prototype program”. Programming Symposium. Lecture Notes in Computer Science. Springer Berlin Heidelberg. 19: 17–32.
- Cohen, B. (1986). The Specification of Complex Systems. Addison-Wesley.
- Paul, Lois (October 11, 1982). “Federal User Offers Free CAD/CAM Software”. Computerworld. 16 (41): 9 – via Google Books.
- Harel, David (January 1980). “And/Or Programs: A New Approach to Structured Programming” (PDF). ACM Transactions on Programming Languages and Systems. ACM. 2 (1): 1–17.– via Weizmann Institute of Science.
- Cushing, Steven (1983). Abstract Control Structures and the Semantics of Quantifiers. EACL. Pisa, Italy.
- Holland, Michael (June 1, 1997). A Constrained Interface Refinement Method for Embedded System Design (Report). Department of Computing, Macquarie University.
- Krut, Robert W. (July 1993). “Overview of Hamilton Technologies, Inc. (HTI) 001” (PDF). Integrating 001 Tool Support in Feature-Oriented Domain Analysis Methodology. Software Engineering Institute of Carnegie Mellon University. pp. 13–15.– via Defense Technical Information Center.
- Ouyang, Meng; Golay, Michael W. (September 1995). An Integrated Formal Approach for Developing High Quality Software for Safety-Critical Systems (Report). Massachusetts Institute of Technology.
- Tedre, Matti (December 3, 2014). The Science of Computing: Shaping a Discipline. CRC Press. p. 120.
- ICSE 2018. “ICSE 2018 – Plenary Sessions – Margaret Hamilton”. YouTube.
- “What to Know About the Scientist who Invented the Term “Software Engineering””. ComputingEdge.Retrieved February 12, 2019.
- Rayl, A.J.S. (October 16, 2008). “NASA Engineers and Scientists – Transforming Dreams Into Reality”. 50th Magazine. NASA.
- Rayl, A.J.S. (October 16, 2008). “NASA Engineers and Scientists-Transforming Dreams Into Reality”. 50th Magazine. NASA.
- “Makers:Margaret Hamilton Videos”. Makers.com.
- “Margaret Hamilton: 2017 Fellow Biography”. Computer History Museum.
- Verne (December 25, 2014). “Margaret Hamilton, the Engineer Who Took the Apollo to the Moon”. Medium.
- Erdogmus, Hakan; Medvidovic, Nenad; Paulisch, Frances (September–October 2018). “50 Years of Software Engineering”. IEEE Software. 35 (5): 20–24.
- Hamilton, Margaret H. (2018). “What the Errors Tell Us”. IEEE Software. 35 (5): 32–37.
- McMillan, Robert (October 13, 2015). “Her code got humans on the moon – and invented software itself”. Wired.
- “Software — and a Woman — at the Heart of Lunar Triumph”. WIRED. August 21, 2014. Archived from the original on May 5, 2016. Retrieved April 29, 2016.
- Luke Kingma. “The Women Who Put Men on the Moon”. Futurism.
- “A moonlit tribute to a moon landing icon”. Google. July 18, 2019. Retrieved December 31, 2019.
Originally published by Wikipedia, 07.29.2010, under a Creative Commons Attribution-ShareAlike 3.0 Unported license.