Every time an astronaut puts on an American spacesuit to conduct a spacewalk at the International Space Station, they pass through a portal installed in part by Janet Kavandi.

It isn’t the only thing the former astronaut did that changed the work of her successors in space. After three missions to orbit, Dr. Kavandi moved into NASA administration, eventually overseeing how astronauts were selected. She’s credited with adding fairness to a process that for the first time chose an astronaut class that included as many women as men.

So when Dr. Kavandi, 60, retired on Monday as director of Glenn Research Center, a Cleveland, Ohio facility that designs innovative technologies for NASA, she le ft not only a legacy in human spaceflight, but also a moon-sized hole for the agency to fill.

Roger Handberg, a space policy expert at the University of Central Florida, called her a role model for women serving in leadership roles at NASA in the future.