If your eight-day work trip was unexpectedly extended by nine months, you might expect to rack up some overtime pay.

Not so for Suni Williams and Butch Wilmore, the NASA astronauts who spent 278 extra days on the International Space Station after their spacecraft malfunctioned. On Tuesday, they splashed down off the Gulf Coast of Florida, ending a saga that had captivated the country since last summer.

But despite their far-flung destination, and the danger and romance of space travel, when it comes to pay, Ms. Williams and Mr. Wilmore are treated effectively like any other government employee who takes a business trip to the next state over.

“While in space, NASA astronauts are on official travel orders as federal employees,” Jimi Russell, a spokesman for the agency’s Space Operations Mission Directorate, said via email.

Ms. Williams and Mr. Wilmore were essentially unable to leave their workplace, a cluster of modules going around the Earth every 90 minutes, for more than nine months. But astronauts aboard the International Space Station receive no overtime, holiday or weekend pay, Mr. Russell said.

Their transportation, meals and lodging are covered, and like other federal employees on work trips, they receive a daily “incidentals” allowance, Mr. Russell said. This is a per diem payment given to employees in the place of reimbursements for travel expenses.

The incidentals allowance for travel to any location is $5 per day, Mr. Russell said.

This means that in addition to their annual salary — about $152,258, according to NASA — Mr. Wilmore and Ms. Williams received around $1,430 for their 286 days in space.

What incidental expenses might Mr. Wilmore and Ms. Williams have incurred while in orbit 250 miles above Earth? It’s unclear. Usually, these are “fees and tips given to porters, baggage carriers, hotel staff, and staff on ships,” according to the U.S. General Services Administration.

Ms. Williams and Mr. Wilmore did not exactly see their extended stay as a hardship. “This is my happy place,” Ms. Williams told reporters in September. “I love being up here in space. It’s just fun, you know?”

Still, if a $5 per diem seems low for a job that causes enough muscle and bone loss for you to need a gurney when you return to Earth, spare a thought for Clayton Anderson, the NASA astronaut who spent 152 days aboard the International Space Station in 2007.

Mr. Anderson said he received a per diem of only about $1.20, or $172 in total.

Being an astronaut was amazing and his dream job, Mr. Anderson said on social media in 2022, “but it IS a government job with government pay.”

He added: “I would have done WAY better with mileage!”