In one giant leap for womankind, the first all-female spacewalk is under way, after an earlier cancelled attempt was mired in controversy.
Flight engineers Christina Koch and Jessica Meir will venture out into the vacuum of space in a historic five-and-a-half-hour mission, which will see them replace a power controller on the International Space Station (ISS).
A total of 227 astronauts and cosmonauts have completed a spacewalk, but only 14 of them have been women – and all of those have done so alongside a male astronaut.
The first woman to perform a spacewalk, officially known as an EVA (Extravehicular Activity), was Soviet cosmonaut Svetlana Savitskaya on the 25 July 1984.
American astronaut Kathryn Sullivan followed her a few months later on 11 October.
NASA has been keen to address gender balance within its astronaut ranks in recent years and currently intends to send the first woman to the moon by 2024.
In an exclusive interview with Sky News, the space agency’s head Jim Bridenstine said he expected this astronaut would be the first member of her crew to step on to the surface, saying: “I would imagine that the next person we have walking on the moon will be a woman.”
The first all-female spacewalk was originally scheduled to take place in March but was cancelled due to spacesuit availability on the International Space Station (ISS).
The cancellation prompted an outcry, with NASA facing accusations of gender discrimination, though Anne McClain, the astronaut involved, later said the decision was made on her recommendation.
Earlier this month, the space agency announced that the all-female spacewalk was back on.
Who are Christina Koch and Jessica Meir?
Mrs Koch, who was part of the original plans for the all-female spacewalk with her then-crew mate Ms McClain, launched to the ISS on 14 March this year.
She has already performed three spacewalks.
Mrs Koch, 40, was selected as an astronaut by NASA in 2013.
A native of Michigan, she graduated from North Carolina State University with a master’s degree in electrical engineering.
Mrs Koch is slated to set a record for the longest single spaceflight by a woman with an expected total of 328 days in space. She is scheduled to remain in orbit until February 2020.
On 25 September, Mrs Koch was joined by Dr Jessica Meir, who will be performing her first spacewalk.
Ms Meir and Mrs Koch were part of the same astronaut class and have trained extensively together.
Ms Meir, 42, holds a master’s in space studies and a doctorate in marine biology.
From 2000 to 2003, she participated in research flights on NASA’s reduced gravity aircraft and served as an “aquanaut” in an underwater habitat for NASA Extreme Environment Mission Operations.
Born and raised in Maine, Ms Meir is a private pilot and is conversational in Swedish and Russian.
She will spend more than six months on the station.
Mrs Koch called Ms Meir her “best friend” upon the latter’s launch into space last month.
Ms Meir later shared photos of Mrs Koch emotionally greeting her on board the ISS after docking, as she fulfilled a “lifelong dream”.
In an interview from the ISS last month, the two women said they feel like “space sisters” because of all the training they have been through together.
They also addressed the cancelled spacewalk in March.
“Jessica and I are held to the exact same training standards. We are treated the same in terms of assignments for various missions on board. And I think that’s the important part,” Mrs Koch said. “Between us and teams on the ground, we don’t see gender as a barrier.”
She said that the cancellation was not a disappointment for her, adding that it was the “correct decision” to accomplish the mission safely.
What is their job on the spacewalk?
Ms Koch and Ms Weir will go outside the ISS to repair a faulty power unit which stopped working over the weekend.
The device, a battery charge-discharge unit (BCDU), has been in use since 2000, but failed to activate after new lithium-ion batteries were installed on the ISS last week.
NASA said it wasn’t impacting the station operations or the safety of the crew.
“The station’s overall power supply, which is fed by four sets of batteries and solar arrays, remains sufficient for all operations.
“However, the faulty power unit does prevent a set of batteries installed earlier this month from providing increased station power,” NASA said.