Enlarge ImageKatherine Johnson received the Presidential Medal of Freedom from President Barack Obama in 2015.

Glenn himself asked for Johnson to re-run the computer calculations prior to his launch.

Enlarge ImageKatherine Johnson's work at NASA's Langley Research Center spanned 1953 to 1986 and included trajectory calculations that helped make early space launches successful

She received the Presidential Medal of Freedom in 2015. 

"When asked to name her greatest contribution to space exploration, Katherine Johnson talks about the calculations that helped synch Project Apollo's Lunar Lander with the moon-orbiting Command and Service Module," NASA says in a biography of Johnson

NASA quoted Johnson in a statement when she accepted the Presidential Medal of Freedom: "I counted everything