Nasa’s record-breaking astronaut Peggy Whitson has retired after spending 665 days in space - more than any other American.
The space agency announced her retirement on Friday, her last day on the job.
She was the first woman to command the International Space Station, holding the position twice, and the oldest woman ever to fly in space.
Ms Whitson was also the world’s most experienced female spacewalker and the first woman to serve as Nasa’s chief astronaut.
The 58-year-old biochemist joined Nasa as a researcher in 1986 and became an astronaut in 1996. Her last spaceflight was last year, her third successive mission.
Nasa officials said Ms Whitson set the highest standards for human spaceflight and was an outstanding role model across the globe.
“It’s been the greatest honor to live out my lifelong dream of being a @NASA Astronaut,” she said via Twitter.
She thanked “all who have supported me along the way”.
“As I reminisce on my many treasured memories, it’s safe to say my journey at Nasa has been out of this world!”
Nasa administrator Jim Bridenstine said Ms Whitson was an inspiration, citing her determination and dedication to science, exploration and discovery.
“She set the highest standards for human spaceflight operations,” Brian Kelly, director of flight operations at Johnson Space Centre in Houston, said.
“As well as being an outstanding role model for women and men in America and across the globe.”
Before leaving the space station last September, Ms Whitson said she would miss the orbiting outpost – an “awe-inspiring creation” – and the views from 250 miles up.
“I will miss seeing the enchantingly peaceful limb of our Earth from this vantage point. Until the end of my days, my eyes will search the horizon to see that curve,” she said.