Tonight’s PBS lineup is devoting all its space to outer space. First up, at 8 pm. ET, is A Year in Space, about astronaut Scott Kelly, who is just completing a year in space – as compared to his twin brother, Mark, also an astronaut, who has stayed home on Earth. And scientists do plan to compare the twins once Scott gets back on terra firma, because that’s the entire point of this year-long experiment. It also sounds like the first act of a ready-made science-fiction thriller, if you ask me. If Scott starts acting strange, and takes Mark’s place and begins to influence the behavior of others, you read it here first. Then, after that one-hour special, PBS at 9 p.m. ET repeats First Man on the Moon, 2014’s Nova profile of Neil Armstrong. And at 10 p.m. ET, there’s a brand-new American Experience installment called Space Men – but it goes back earlier in time than you’d expect. It’s about balloonists, the first to actually venture into the lip of “outer space.” Check local listings.