Scott Kelly has had quite a year. The 52-year-old astronaut has spent the last 340 days in space, breaking records, conducting experiments, taking incredible pictures, and tweeting up a storm. But all good things must come to an end, and tomorrow, March 1, Kelly will return to Earth.

Kelly’s stint aboard the International Space Station (ISS) was conceived as part of NASA’s “One-Year” study, which will look at the effects of long-term space travel on the human body. The experiments have a special twist: Scientists on Earth have also been monitoring Kelly’s twin brother Mark Kelly, a retired astronaut. Because his genes are nearly identical to his brother's, Mark represents an excellent control group. 

But Scott Kelly’s investigations in space go way beyond his own body. He’s conducted more than 400 experiments, many of which he captured in delightful YouTube videos.

Kelly has also had plenty of laughs. Just last week he donned a gorilla suit, simply because he could. “Needed a little humor to lighten up a #YearInSpace,” he tweeted. “Go big, or go home. I think I’ll do both.” 

To celebrate Kelly's return, PBS will air the first installment of A Year in Space, which follows the astronaut and his family on Earth as he prepares for and executes his mission. You can watch A Year in Space Wednesday, March 2 at 8 p.m. EST.