Johnston began working at the
Marshall Space Flight Center (MSFC) of NASA during her engineering studies from 1963 to 1968. In 1968, she became employed there as a metallurgist. These tests included some in the neutral buoyancy simulator, itself a mock-up of one to be built in Europe to provide training for future astronauts. Johnston led three science experiments, and helped her fellow scientists to develop techniques to be used on Spacelab. In 1976, she indicated that she "had planned the work in hopes of going on orbital missions in the 1980s." In 1976, Johnston worked with Griner on MSFC experiments testing space-like conditions with Space Processing Applications Rocket (SPAR) launched objects, particularly involving "
dendrite remelting and
macrosegregation". and
Carolyn S. Griner in training as a candidate payload specialist for space missions in 1973 With Whitaker and Griner, Johnston received astronaut training. Her training included tests in the pool of the MSFC neutral buoyancy laboratory and a flight in microgravity aboard the
Boeing KC-135 Stratotanker, as well as completing additional flight lessons. not flying – she never went to space. For Spacelab, Johnston was selected as a scientist, specifically for her knowledge in materials science, one of the mission's primary purposes. Of her selection, mission manager
Joseph Cremin wrote: "The job ahead is difficult and the time is short which makes this assignment a significant challenge that will require the utmost dedication and perseverance of Dr. Johnston. I have no doubt that she will accomplish this assignment in an exemplary fashion." ==Later career==