Peggy Whitson: Record-holding astronaut

Peggy Whitson Talks from ISS
NASA astronaut and space station crewmember Peggy Whitson speaks with a representative of the Guinness Book of World Records on July 26, 2017. (Image credit: NASA TV)

Peggy Whitson is a record-breaking astronaut who has worked for both NASA and Axiom Space. 

She has spent more time in space than any other American or woman, and those are only two of the records she holds. Whitson retired from NASA on June 15, 2018, after three missions but kept flying and went on to command Axiom Space's Ax-2 mission in 2023.

Whitson's many milestones also include becoming the first woman to command the space station twice, the first female and nonmilitary head of NASA's astronaut office, and the first woman to command a private space mission.

Related: In photos: Record-breaking NASA astronaut Peggy Whitson 

Peggy Whitson FAQs

How many days has Peggy Whitson spent in space?

Whitson has spent a cumulative 675 days in space — more than any other American or woman.

How many space missions did Peggy Whitson fly on?

Whitson has flown on four space missions: three with NASA and one with Axiom Space.

Joining NASA

Peggy Annette Whitson was born on Feb. 9, 1960, in Mount Ayr, Iowa. After earning her bachelor of science degree in biology and chemistry from Iowa Wesleyan College in 1981, she earned her doctorate in biochemistry from Rice University in Texas in 1985, according to her official NASA biography. Whitson then served as a National Research Council resident research associate at NASA's Johnson Space Center (JSC), and later as supervisor of the biochemistry research group at KRUG International, a medical sciences contractor at JSC. She was also an adjunct assistant professor at both the University of Texas and Rice University.

On May 6, 1989, Whitson married Clarence F. Sams. Sams, also a biochemist, had joined NASA in 1984, researching the biological effects of spaceflight at the cellular and subcellular levels.

Also in 1989, Whitson began work as a research biochemist at JSC, serving as a technical monitor of its biochemistry research laboratories. In 1992, she was named the project scientist for the Shuttle-Mir program, in which NASA space shuttles visited and carried crewmembers to and from Russia's Mir space station, spending three years in that role. She also served as deputy division chief of JSC's medical sciences division.

Whitson's journey to becoming an astronaut

In 1996, Whitson was selected as an astronaut candidate for NASA, and she started training in August of that year. After two years of training and evaluation, she became eligible for flight duties with the rest of her astronaut class. Because astronauts take on ground duties when not training for a mission, Whitson was then assigned technical duties in JSC's astronaut office operations planning branch. Whitson also served as the lead for the crew test support team in Russia from 1998 to 1999, during the early days of the International Space Station (ISS) program that included Russian cosmonauts.

Whitson's first assignment was as part of the long-duration Expedition 5 crew. On June 5, 2002, Whitson launched for the ISS and served there for six months. Named the first NASA science officer during her stay in space, Whitson conducted 21 investigations in human life sciences and microgravity sciences. She returned to Earth on Dec. 7, 2002, logging 184 days, 22 hours and 14 minutes in space.

For several years, Whitson then took on a series of high-profile ground responsibilities. In 2003, she commanded the underwater NEEMO (NASA Extreme Environment Mission Operations) mission, which simulated aspects of spaceflight. Whitson also served as deputy chief of the JSC astronaut office between November 2003 and March 2005, including being a member of the 2004 selection board for astronaut candidates. 

Whitson stepped down from her management role at the astronaut office to become eligible for missions again, as NASA rules stipulate that the office's management cannot fly to space. From March to November 2005, she was chief of the station operations branch at JSC's astronaut office, where she played a key role in ISS mission planning. She then trained as backup ISS commander of Expedition 14 from November 2005 to September 2006, before being assigned to her next mission. 

NASA astronaut Peggy Whitson is pictured with an Orbital ATK Cygnus spacecraft (left) during a May 12, 2017 spacewalk outside the International Space Station. Whitson, the station's commander, and fellow NASA astronaut Jack Fischer will conduct a repair spacewalk on Tuesday, May 23. (Image credit: NASA)

First female space station commander

Whitson returned to space on Oct. 10, 2007, as part of Expedition 16 — this time, as the first female station commander. Along with Pamela Melroy, she was one of the first two women to lead missions at the same time. (Melroy led a 13-day shuttle mission.) While on board the ISS, Whitson oversaw the first expansion of the station's living and working space in more than six years. She returned to Earth on April 19, 2008, after 191 days, 19 hours and 8 minutes in space. At that time, she had accumulated the most time in space for any woman. During Whitson's fifth overall extravehicular activity (EVA), she surpassed Sunita Williams as the woman with the most spacewalks; she would make one more spacewalk by the end of the mission.

It would be almost a decade before Whitson returned to space. Whitson served as chief of the astronaut corps from 2009 to 2012, making her the first female, nonmilitary individual to hold that position. She was responsible for the mission preparation activities and on-orbit support of all ISS crews and their support personnel.

Although she enjoyed the job, she wasn't ready to say goodbye to space.

"It was actually a very satisfying job, but I did know that I still wanted to fly again — at least, I was not willing to say I didn't want to fly anymore," Whitson said in a YouTube video for AARP. "So that's when I stepped down to get back in line [for a flight]." 

Record-breaking trip to space

On Nov. 17, 2016, Whitson once again launched into space as part of Expedition 50/51. At age 56, she immediately became the oldest woman to go to space (a record that would be broken by Wally Funk in 2021). Whitson also became the only woman to command the space station twice.

Although the initial plan was for Whitson to spend three months in space, her stay on the ISS was extended by three months. She returned home on Sept. 3, 2017, after clocking 289 days, 5 hours and 1 minute in space and attaining the record for the most cumulative days in space for an American, as well as for a woman of any nationality.

"I haven't felt bored since I got here in November last year," Whitson said from orbit in a video interview with a representative of Guinness World Records on July 26, 2017. "I think if you have the right attitude, you can stay in space for a long period of time, and it's actually very satisfying and enjoy[able]."

While in space, Whitson performed four additional spacewalks, bringing her total to 10 and putting her in a tie for first place with Michael Lopez-Alegria for the most spacewalks performed by a NASA astronaut. She also clocked the most time spent by a woman performing spacewalks.

"I feel like the reason I'm here is to do my job, and I'm going to do it to the best of my abilities," she said in the interview with Guinness World Records. "The records, I think, are important for NASA, to demonstrate what we're doing, how we're expanding and what we're improving on. And that continual improvement, that continual expansion of our records, is an important one for all of us at NASA, not just me."

Axiom Space 

Although Whitson retired from NASA in 2018, she wasn't done flying in space. In 2022, she joined Axiom Space, a Houston-based company that was just starting to fly its own missions to the ISS with SpaceX Dragon spacecraft. Whitson became the first female commander of a private mission with Ax-2, the second Axiom mission, which flew for about 10 days in May 2023.

Whitson is also director of human spaceflight at Axiom and was on the mission to fulfill a NASA requirement: All private missions, per agency rules, must be commanded by a former agency astronaut. Joining Whitson were paying customer and pilot John Shoffner and the first two Saudis to visit the ISS: astronauts Ali AlQarni and Rayyanah Barnawi. (Rayyanah was also the first Saudi woman to go to space.)

As of the end of Ax-2, Whitson's tally of days in space is 675, according to Axiom Space. Whitson remains active with the company, which may bring her to space again.

After Whitson's 2023 flight, CBS asked whether she would like to go to the moon one day. 

"I'd have fun doing that one," Whitson said. "But there's just a lot of opportunities. I think, as space is changing so much, there are lots of ways to contribute and be a part of that. I think it's part of the reason I like to keep going back. Besides the addiction of this perspective, I really like being a part of something bigger than me. Space truly is that, and the objectives in space are that. So I'm very excited about continuing." 

Records Whitson set

These records were current at the time of the listed mission and may have changed in the intervening years.  

Expedition 16 

  • One of the first two women to lead missions at the same time 
  • Oct. 10, 2008: First female commander of the ISS
  • Dec. 16, 2008: Most cumulative spacewalk time for a woman (a record achieved during her fifth spacewalk), at 32 hours, 36 minutes  

Astronaut Office

  • 2009: First female, nonmilitary chief of the astronaut office 

Expedition 50/51/52 

  • Nov. 17, 2016: Oldest woman to go to space, at age 56; and first woman to command the ISS twice 
  • March 30, 2017: Most spacewalking time accumulated by a female astronaut 
  • April 24, 2017: Most cumulative days in space by an American and by a woman of any nationality (534 days, 2 hours, 48 minutes; when she landed, she had clocked 665 total days in space)  
  • May 23, 2017: On her 10th spacewalk, tied with Michael Lopez-Alegria for most spacewalks by a NASA astronaut 
  • Nov. 17, 2017: With 665 days in space, Whitson held the record for the most days in space for an American astronaut and the most for a woman of any nationality. On the all-time spaceflight endurance list, she sat at No. 8. 

Peggy Whitson Q&A

Peggy Whitson holds the record for the most time in space by an American and by any woman in the world. (Image credit: Axiom Space)

Peggy Whitson bio

Peggy Whitson holds the record for the most time in space by an American and by any woman in the world. Her latest mission was the 10-day Axiom Space Mission 2 (Ax-2). Before that, she had accumulated 665 days in space as a NASA astronaut across three missions, during which she commanded the International Space Station twice and performed the most spacewalks of any woman.

Tell us about the Ax-2 mission.

The Ax-2 mission had a couple of really important objectives: to increase access for private and government astronauts, and [for] scientists as well. We succeeded in doing that. 

What's harder: preparing for space or for reentry?

For me, it's actually the landing. My body doesn't adapt well to being back in gravity. I think it just loves being in space more. 

Why did you decide to work for a private space company after retiring from NASA?

I might be a little bit addicted to space. But it was exciting to me to be a part of this change in space. Governments have pretty much led the way in space because it's so expensive, but commercial entities now are providing some of the leadership. 

This interview is based on a joint exclusive interview with Whitson made public on July 20, 2023. 

Additional resources

Read about ISS record holders like Whitson in this NASA feature. Learn about the space station that Axiom is slowly working to build on this Axiom Space webpage.  


AARP. (2016, Nov. 16). "NASA astronaut Peggy Whitson breaks records | Disrupt aging." 

Axiom Space. (2023.) "Peggy Whitson." 

CBS. (2023, July 19.) "America’s most experienced astronaut Peggy Whitson on overcoming 4 rejections from NASA." 

Guinness World Records. (2017, July 28.) "Space interview with NASA astronaut Dr. Peggy Whitson — Guinness World Records." 

NASA. (2018, Dec. 14.) "Peggy A. Whitson (Ph.D.) NASA astronaut."  

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Elizabeth Howell
Staff Writer, Spaceflight

Elizabeth Howell (she/her), Ph.D., is a staff writer in the spaceflight channel since 2022 covering diversity, education and gaming as well. She was contributing writer for for 10 years before joining full-time. Elizabeth's reporting includes multiple exclusives with the White House and Office of the Vice-President of the United States, an exclusive conversation with aspiring space tourist (and NSYNC bassist) Lance Bass, speaking several times with the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?", is co-written with astronaut Dave Williams. Elizabeth holds a Ph.D. and M.Sc. in Space Studies from the University of North Dakota, a Bachelor of Journalism from Canada's Carleton University and a Bachelor of History from Canada's Athabasca University. Elizabeth is also a post-secondary instructor in communications and science at several institutions since 2015; her experience includes developing and teaching an astronomy course at Canada's Algonquin College (with Indigenous content as well) to more than 1,000 students since 2020. Elizabeth first got interested in space after watching the movie Apollo 13 in 1996, and still wants to be an astronaut someday. Mastodon: