WASHINGTON - US space agency NASA, Russia's federal space agency Roscosmos, and their international partners have selected two veteran spacefarers for a one-year mission aboard the International Space Station in 2015, said a statement issued Monday from NASA.

The two, Scott Kelly and Mikhail Kornienko, will launch aboard a Russian Soyuz spacecraft from the Baikonur Cosmodrome in Kazakhstan in spring 2015 and will land in Kazakhstan in spring 2016.

The goal of their yearlong expedition aboard the orbiting laboratory is to understand better how the human body reacts and adapts to the harsh environment of space.

They will collect scientific data important to future human exploration of the solar system during the mission.

The Data will help inform current assessments of crew performance and health and determine better and validate countermeasures to reduce the risks associated with future exploration.

"The one-year increment will expand the bounds of how we live and work in space and will increase our knowledge regarding the effects of microgravity on humans as we prepare for future missions beyond low-Earth orbit," said NASA Associate Administrator William Gerstenmaier.

Kelly and Kornienko will begin a two-year training program early next year in the United States, Russia and other partner nations.

Kelly was a backup crew member for the station's Expedition, where Kornienko served as a flight engineer.