NASA Astronauts Jessica Meir and Christina Koch take part in the first all-female spacewalk when they venture out of the International Space Station to replace a power controller.

The NASA Astronaut Corps is a unit of the United States National Aeronautics and Space Administration (NASA) that selects, trains, and provides astronauts as crew members for U.S. and international space missions. It is based at Johnson Space Center in Houston, Texas.

Jessica Ulrika Meir is an American NASA astronaut, marine biologist, and physiologist. She was previously an assistant professor of anesthesia at Harvard Medical School, Massachusetts General Hospital, Boston, following postdoctoral research in comparative physiology at the University of British Columbia. She has studied the diving physiology and behavior of emperor penguins in Antarctica, and the physiology of bar-headed geese, which are able to migrate over the Himalayas. In September 2002, Meir served as an aquanaut on the NASA Extreme Environment Mission Operations 4 crew. In 2013, she was selected by NASA to Astronaut Group 21. In 2016, Meir participated in ESA CAVES, a training course in which international astronauts train in a space-analogue cave environment. Meir launched on September 25, 2019, to the ISS onboard Soyuz MS-15, where she served as a flight Engineer during Expedition 61 and 62. On October 18, 2019, Meir and Christina Koch were the first women to participate in an all-female spacewalk.

Christina Koch is an American engineer and NASA astronaut of the class of 2013. She received Bachelor of Science degrees in electrical engineering and physics and a Master of Science in electrical engineering at North Carolina State University. She also did advanced study while working at the Goddard Space Flight Center. Just before becoming an astronaut, she served at the National Oceanic and Atmospheric Administration as station chief for American Samoa.

Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable Earthlike atmosphere, the astronaut is completely reliant on a space suit for environmental support. EVA includes spacewalks and lunar or planetary surface exploration. In a stand-up EVA (SEVA), an astronaut stands through an open hatch but does not fully leave the spacecraft. EVAs have been conducted by the Soviet Union/Russia, the United States, and China; astronauts from Canada, Japan, Brazil, the United Arab Emirates, and the European Space Agency have also participated in EVAs conducted by those nations.