NASA and Roscosmos have selected two veteran International Space Station (ISS) crewmembers for a yearlong assignment to the 14-year-old orbiting science laboratory that is intended to shed new light on human adaptation to long-duration spaceflight and other challenges facing explorers on future deep-space missions.

Scott Kelly, a 48-year-old U.S. Navy captain, and Mikhail Kornienko, a 52-year-old RSC Energia test engineer, will begin a two-year training program for the mission early next year.

They will launch from the Baikonur Cosmodrome in Kazakhstan aboard a Russian Soyuz spacecraft in the spring of 2015 and return to the Kazakh plains aboard a Soyuz as well, according to Nov. 26 announcements from Roscosmos and NASA. Officials from the two primary partners in the 15-nation space station program plan an early December briefing to elaborate on the mission details, according to NASA station program spokesman Josh Byerly.

The two men will participate in health and space technology-related investigations on crew performance during deep-space missions and the countermeasures intended to fend off the ill effects that have surfaced during the standard, 4-6 month assignments to the six-person ISS.

“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 Bill Gerstenmaier, NASA’s associate administrator of human exploration and operations.

During a dozen years of continuous station staffing, researchers have made strides in overcoming muscle and bone deterioration in weightlessness with daily workout regimes on specially designed exercise equipment, as well as tailored diets and medication. However, new issues have also surfaced, including reports of temporary blurred vision that mimics the symptoms of idiopathic intracranial hypertension. The vision issue is a focus of recent research emphasis.

In April 2010, President Barack Obama directed NASA to prepare for a human mission to a near Earth asteroid in 2025 as a precursor to the eventual exploration of Mars — voyages that would require two to three years using current propulsion technologies. More recently, NASA officials have also expressed an interest in an orbiting lunar base to gather deep-space experience. In Russia, policy makers have spoken recently of plans for a lunar base.

Kelly, who was selected by NASA for astronaut training in 1996, has launched three times, most recently in late October 2010 to serve as the ISS commander during a 160-day tour of duty. Kelly has logged 181 days in orbit over a career that includes two NASA shuttle missions.

Kornienko, who joined RSC Energia in 1995, served as an ISS flight engineer during a 176-day mission in 2010.

Soviet cosmonaut and physician Valery Polyakov holds the world’s record for the longest spaceflight, 438 days, set aboard Russia’s former Mir space station in 1994-95.

Michael Lopez-Alegria, president of the Commercial Spaceflight Federation, holds the current U.S. record for long-duration spaceflight, 215 days, set aboard the ISS in 2006-07 while he was a NASA astronaut. NASA astronaut Sunita Williams holds the world’s record for the longest spaceflight by a woman, 195 days, set during her 2007 stay aboard the ISS.