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The six crewmembers on the International Space Station each have their own phone-booth-size sleeping cabin, but they all jammed into one for a fun photo op.

Ricky Arnold, a NASA astronaut who has been in space for more than five months, posted the photo to Twitter Monday (Aug. 27). Arnold is bursting out of the crew cabin with American astronauts Drew Feustel and Serena Auñón-Chancellor, Russian cosmonauts Oleg Artemyev and Sergey Prokopyev, and German astronaut Alexander Gerst.

The six of them have been busy on Twitter lately, celebrating Feustel's birthday, checking the Soyuz spacecraft in matching duds and revealing the secret propulsion systempowering the space station. (Feustel, Auñón-Chancellor and Gerst also played the first-ever tennis match in space last week.) [Sleeping in Space: How Astronauts Get a Good Night's Rest]

But it's not all fun and games: According to NASA's space station blog, the crewmembers have been busy running experiments on the orbiting lab and maintaining their home. For example, on Friday Auñón-Chancellor worked on the exercise treadmill and replaced parts; Gerst exercised wearing a SpaceTex-2 shirt to test out its cooling properties; Feustel released two little in-station robots called SPHERES; and Arnold worked on an Earth-watching experiment and reinstalled a botany platform.

The crewmembers also just recently sent away a Russian cargo ship and will welcome a Japanese resupply mission in September, and they worked on protein crystal experiments and tested a sextant to aid in navigating through space.

NASA could not confirm which crewmember's quarters was the site of the photo shoot, but there are four of them visible in the shot — each of the four sides of NASA's Harmony module seen in the photo (and video) hosts a crew cabin with an individual astronaut's laptops and personal effects. Two more astronauts have crew quarters in the Russian segment of the spacecraft.

During the changeover between missions there are occasionally nine people on the space station at once — astronauts without crew quarters bring sleeping bags to their own smaller spaces, Japanese astronaut Kimiya Yui said during an on-orbit interview in 2015. During NASA's space shuttle program, the station's population sometimes reached a high of 13 (including the shuttle's 7-person crew), though shuttle astronauts typically slept on their own spacecraft.

Arnold, Feustel and Artemyev will head home from the space station in October, while Auñón-Chancellor, Gerst and Prokopyev will be on board until December.

Email Sarah Lewin at slewin@space.com or follow her @SarahExplains. Follow us @Spacedotcom, Facebook and Google+. Original article on Space.com