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The Russian Soyuz TMA-21 spacecraft, carrying the ISS crew, blasts off from the Baikonur cosmodrome in Kazakhstan on April 4. The craft, carrying three astronauts, docked with the International Space Station on Wednesday.

A Russian capsule delivered three new astronauts to the International Space Station on Wednesday, doubling the size of the crew just in time for a pair of major space anniversaries.

The Soyuz spacecraft docked two days after blasting off from Kazakhstan. The linkup took place 350 kilometres above the Andes Mountains of Chile.

Settling in for a five-month mission are Russians Andrey Borisenko and Alexander Samokutyaev, and American Ronald Garan Jr.

They join three astronauts — a Russian, an American and an Italian — who are just a month away from returning to Earth.

On Tuesday, all six will mark the 50th anniversary of the first human in space, Soviet cosmonaut Yuri Gagarin. The newly arrived Soyuz bears the space pioneer's name.

The 30th anniversary of the first space shuttle launch falls on the same day, April 12.

NASA, meanwhile, said space station operations will be unaffected if the U.S. government shuts down this weekend.

Space shuttle Endeavour is due to blast off at the end of this month with a $2-billion US physics experiment for the space station.

Atlantis will close out the shuttle program this summer. NASA officials are uncertain what impact a government shutdown would have on those launch dates.

Until private companies come up with a way to ferry Americans to and from the space station, NASA will continue to pay the Russian Space Agency to do so, via the Soyuz. Each seat costs tens of millions of dollars.

Wednesday marked Italian astronaut Paolo Nespoli's 54th birthday.