Twin astronauts Scott and Mark Kelly were separated for almost a year, undergoing intensive measurements when one was in space and one was on Earth. But that was only the beginning of their scientific odyssey. “Beyond A Year in Space,” PBS and Time’s follow-up documentary to last year’s — which followed Scott Kelly from launch to landing — chronicles Kelly’s return to life on Earth and the extensive medical testing the duo undergo to determine exactly what changes have occurred as a result of his record-breaking stay on the International Space Station. The documentary also follows two new astronauts, Jessica Meir and Victor Glover, training to go even further.