On February 29, the NASA astronaut Scott Kelly will turn over command of the International Space Station to astronaut Tim Kopra, then prepare to return to Earth after spending nearly a year in space. Last March, Kelly and cosmonaut Mikhail Kornienko launched into low Earth orbit aboard the ISS, and have since participated in hundreds of experiments while the effects of long-term microgravity on the human body were studied. Kelly also took hundreds of photographs during his year abroad, posting many to his Twitter account. As we await the return of Kelly and Kornienko tomorrow, here are some of his photographs from the past year.