The 1967 NASA technical note D-4246, Midcourse Guidance Procedure with Single Position Fix Obtained From Onboard Optical Measurements describes correcting the trajectory of a spacecraft traveling between the moon and Earth, using an on-board telescope to point at stars or other fixed objects in space. This method was later used to correct the flight of Apollo 13.

Who were the authors of this paper? Did they include anyone notable?

This question is part of a series honoring the 50th anniversary of Apollo 13, "NASA's finest hour".

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    $\begingroup$ The mathematics was developed by Sir Isaac Newton. The authors of that paper applied the mathematics to the problem of the electrifying mid-course correction. $\endgroup$
    – J...
    Apr 16, 2020 at 19:41

1 Answer 1


The authors of the paper are Harold A. Hamer, Katherine G. Johnson, and W. Thomas Blackshear. Of these, the name Katherine Johnson might ring a bell with people, as she was one of the protagonists in the 2016 movie Hidden Figures, honouring the women that were instrumental in the early days of the US space program.

Katherine Johnson and her colleagues were computers, i.e. people (mostly women) that manually computed numerical values for given mathematical equations. Johnson was brilliant at math and her mastering of the math needed for orbital spaceflight and rendezvous was instrumental for the early years of the program, to the point where John Glenn refused to go on his orbital flight unless Johnson had personally checked all the computations.

Given the order of the names, it is likely that Harold A. Hamer was Johnson's direct supervisor or boss and W. Thomas Blackshear a colleague, although I can't verify that.

Katherine Johnson

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    $\begingroup$ There was no rendezvous of spacecrafts in orbit during the early years of spaceflight during the Mercury program. Aldrin's doctoral thesis was Line-of-Sight Guidance Techniques for Manned Orbital Rendezvous in 1963. $\endgroup$
    – Uwe
    Apr 15, 2020 at 19:35
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    $\begingroup$ @Uwe Johnson didn't just quit after Mercury. She also worked on Apollo and the STS program. Feel free to change the phrasing if it's not accurate enough. $\endgroup$
    – Ludo
    Apr 15, 2020 at 19:43
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    $\begingroup$ Johnson and Hamer are in my August 19, 1960 copy of the Langley phone book. Blackshear's name is not in it. They were both in the Flight Mechanics Branch in the Aero-Space Mechanics Division. $\endgroup$ Apr 15, 2020 at 19:45
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    $\begingroup$ The document in the question is 7 years newer than the phone book, so Blackshear could easily have joined later. $\endgroup$ Apr 15, 2020 at 19:52
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    $\begingroup$ Hope you don't mind that I added a picture of Johnson. $\endgroup$
    – DrSheldon
    Apr 15, 2020 at 19:57

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