International Space Station Commander Bill McArthur and Flight Engineer Valery Tokarev will vacate the orbiting facility temporarily March 20 to move a Soyuz spacecraft.

"It's like shuffling parking spaces in your driveway," NASA spokesman Allard Beutel told SpaceDaily.com.

Beutel explained the maneuver is necessary to free the docking port in the Russian Zarya module for the March 31 arrival of another Soyuz carrying the next station crew, including Expedition 13 Commander Pavel Vinogradov and Flight Engineer Jeff Williams.

Early Monday morning Eastern Time, Tokarev will undock the Soyuz and along with McArthur will fly the Soyuz free of the station for about 35 minute flight, moving the craft from the Zarya port to the aft docking port of the Zvezda living quarters module.

Though the task is considered routine, it is not without complications. McArthur and Tokarev first must prepare the space station to operate temporarily without a crew, in case some unforeseen event requires them to return to Earth prematurely on the Soyuz. They also have to prepare the spacecraft for a possible re-entry flight before they detach it from the Zarya port.

The next station crew will launch March 29 from the Baikonur Cosmodrome in Kazakhstan, along with Brazilian Space Agency astronaut Marcos Pontes, who will spend about a week on the station before returning with McArthur and Tokarev.

The arriving Soyuz will spend about six months docked at Zarya, Beutel said.