Astronauts aboard the International Space Station are carrying out two important household tasks Monday: one, a spacewalk to do maintenance; the other, fix the toilet.

Astronauts David Wolf and Thomas Marshburn celebrated the 40th anniversary of man's first lunar landing by venturing out to hook up spare parts to the International Space Station.

It is the second spacewalk in three days, and takes place 40 years to the day that Neil Armstrong and Buzz Aldrin walked on the moon.

Astronauts remaining inside the ISS, meanwhile, have a far less glamorous job: to get the toilet working.

One of the station's two commodes malfunctioned Sunday. NASA says the problem is a failed pump  which adds chemicals to the system to separate liquids from solid waste.  

With a record setting combined crew of 13 astronauts aboard, time is of the essence.

"They have 13 people, and the idea is that typically you'd want to have two washrooms for every six astronauts you have on the space station," said space expert Sara Poirier, a researcher at the Ontario Science Centre.

Poirier told CTV's Canada AM on Monday that using the space commode is "not a quick in and out procedure."

There is one more toilet available, aboard the attached Shuttle Endeavor, but its use is limited.

"The problem is that you can't use the shuttle for backup for that long because they can't empty out the dirty water tanks because they're attached to the space station," Poirier said.

The spacewalk will begin at 10:28am Eastern, and will involve using the Canadian-made Canadarm 2 to move astronauts along the ISS components.

Aboard the station are Canadians Julie Payette and Robert Thirsk. 

They represent a major milestone for Canada -- it's the first time two Canadians have been in space at the same time.

On Monday, Roberta Bondar, Canada's first woman in space, paid tribute to the Canadian pair, and to Canadian space technology.

"Bob Thirsk is going to be in space for quite a long time. It's quite interesting. He's a physician, I'm a physician. We'll be interested in looking at some of his medical issues when he comes back," Bondar told CTV News Channel.

"Julie is up there for just over 2 weeks, to move that Canadarm, another piece of Canadian technology on both the space station and shuttle, " she said.

Bondar flew aboard shuttle Discovery in 1992.

On Sunday Payette and Thirsk held a joint press conference.

Payette, a member of the Endeavour crew, joined Thirsk at the space station on Friday. But while Payette is spending 16 days at the ISS, Thirsk is currently on a six-month mission.

Thirsk answered questions from Gary Goodyear, Canada's minister of state for science and technology, about what it's like to live in a giant, hulking metal structure orbiting the planet.

"If you're the type of person who enjoys camping, you'll love it here," he said.

"Living aboard the space station is like camping out. It's not a hotel lifestyle, it's more of a rustic lifestyle."

In true camping fashion, Thirsk's bed is a sleeping bag, although it's located in the middle of a laboratory. And because of the zero gravity, he said it feels like a water bed.

The only issue is privacy, but Thirsk said he's grateful to be in the company of Payette and the other astronauts.

"We're all very good colleagues; we respect each other," he said. "It's a real joy to work with these people every day and I love having everyone around."

He also said the space station is large enough that it never feels too crowded.

"Be aware that the space station is not a small space vehicle," he said. "It's very, very large. It's perhaps the same interior as a 747 aircraft."