Along with Russian cosmonaut Mikhail Kornienko, Kelly will spend nearly a full year aboard the International Space Station. That's close to the record time spent in space (14 months undertaken in 1994 on the Russian Mir station) and the longest anyone has spent in space since then. It's also going to break the record for the longest time spent on the International Space Station, and Kelly will break NASA's spaceflight length record by about five months.
To add to the excitement, Kelly's twin (Mark Kelly, a retired astronaut) has volunteered to spend his year being poked and prodded as much as his space-bound brother will be. Scientists across the country submitted research proposals in hopes of taking advantage of this twin study data, and the 10 selected experiments will examine how spaceflight affects everything from gut bacteria to DNA expression.
Cosmonaut Gennady Padalka also launched with Kornienko and Kelly, though he'll only spend the standard six months aboard ISS before returning to Earth. But Padalka, who's made three trips to ISS and spent time on Russia's now-defunct Mir station, is breaking a record as well: He's spent more than 710 days in space already, and once he finishes his current jaunt, he'll have broken the world record (currently held by Sergei Krikalev with 803 days) for total time spent off the Earth.
Kelly and his crewmates should reach ISS about 9:30 p.m. ET.