U.S. astronaut Scott Kelly, along with Russian cosmonauts Mikhail Kornienko and Gennady Padalka, arrived on the International Space Station after taking off aboard a Russian Soyuz capsule on Friday, marking the start of an orbital stay that could set two records. Kelly and Kornienko will spend almost a year on the station, which in Kelly's case will best the U.S. record for longest-duration spaceflight by more than 100 days. The men will undergo intense medical monitoring for studies aimed at determining how ultra-long-term spaceflight affects the human body. Russian cosmonauts have been in space continuously for as long as 437 days, so Kelly and Kornienko won't set a world record. But Padalka has his own record to set: If he stays in orbit until his scheduled return in October, he'll chalk up an unprecedented cumulative total of nearly 900 days in space.