* Mission would help prepare for flights beyond Earth

* Cosmonaut Valery Polyakov spent 438 days in orbit

* Longest flight by U.S. astronaut is 215 days

CAPE CANAVERAL, Fla., Oct 4 (Reuters) - NASA is considering

doubling the amount of time an astronaut spends at the

International Space Station to a year, laying the groundwork for

future missions deeper into space, officials said Thursday.

If approved, a mission likely would begin in 2015, said NASA

spokesman Rob Navias.

Russian news agency RIA Novosti reported this week that the

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NASA, Russia eye yearlong space station assignments