On March 27, 2015, NASA astronaut Scott Kelly and Russian cosmonaut Mikhail Kornienko launched to the International Space Station (ISS). Now, almost one year on, they’re preparing to return to Earth from their groundbreaking mission.

Kelly and Kornienko, together with Russian cosmonaut Sergey Volkov who has been on the station for 6 months, will undock from the ISS at 8.05 p.m. EST on Tuesday, March 1 (1.05 a.m. GMT on Wednesday, March 2). Almost three hours later, at 11.27 p.m. EST (4.27 a.m. GMT), they will touch down in Kazakhstan, 342 days since they left Earth.

It’s set to be a pretty momentous day, and there are plenty of ways to get involved. NASA television will begin coverage of the entire undocking and landing tomorrow from 3.10 p.m. EST (8.10 p.m. GMT), when you can watch Kelly hand over command of the station to fellow NASA astronaut Tim Kopra. We’ve embedded the live stream below for you to tune in.

^{Coverage of Scott Kelly's departure will begin on Tuesday March 1 at 3.10 p.m. EST (8.10 p.m. GMT)}

On Twitter, you can follow along with #YearInSpace and pose questions to #askNASA. And on Friday, there will be both a press conference on NASA TV, and a Q&A on Reddit with scientists and medical doctors from NASA’s Johnson Space Center.

Kelly and Kornienko are the first astronauts to spend this long on the ISS in a single mission, with previous missions lasting only 6 months. One goal of the mission is to see if humans can cope with prolonged spaceflight, something that will be a necessity for return trips to Mars, which could last up to 3 years. In a recent press conference, Kelly said he was feeling great aboard the ISS, joking: “I could go another year if I had to.”

During the mission Kelly’s twin brother Mark Kelly, a former astronaut, remained on the ground. Scientists have been testing both Scott and Mark and will study how spaceflight has affected one brother compared to the other on Earth.

This mission will only place Kelly and Kornienko fourth on the all-time list of the 10 longest human spaceflights, though. The top three were all set aboard the Mir space station, with the longest being Russian Valeri Polyakov’s stay from January 1994 to March 1995, which lasted 437 days.

But it's still a hugely significant mission, and it brings us ever closer to one day seeing humans set foot on the surface of Mars.