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 experimental yearlong endurance mission would include a Russian cosmonaut and a NASA astronaut.

“If the mission proves to be effective, we will discuss sending yearlong missions ... on a permanent basis,” Alexei Krasnov, head of human spaceflight with the Russian space agency Roscosmos, said in the RIA Novostia report.

Navias said an agreement had not yet been signed.

“NASA has been exploring the idea of a one-year increment on the space station,” Navias said. “That would be a natural progression as part of preparations for missions beyond low-Earth orbit.” The agency had previously planned missions at no more than six months.

Medical and biological studies are key areas of research aboard the station, a $100 billion, permanently staffed laboratory a partnership of 15 countries, that flies about 250 miles (400 km) above Earth.

Doctors are particularly concerned about the effect of long stays in the weightless environment of space has on bone loss, vision changes and impacts to an astronaut’s cardiovascular system.

Russian cosmonaut Valery Polyakov holds the record for the longest spaceflight, a 438-day mission aboard Russia’s Mir space station in 1994 and 1995.