How did the even know about space?

They can't see. They use a sonar like ability, but noise doesn't bounce off of stars or the vacuum of space. They live in a world of darkness, even though they can't see, their sky is just as dark as space. Maybe they can hear the weather patterns but at some altitude, it just fades to nothing. Maybe they measure the density and temperature of the atmosphere. What was their space program like? Does their sonar reach as far as our sight? We can see accurately and in detail for many miles, so when an astronaut lands back on Earth, we just watched them land and then go get them. I guess Eridians just triangulate radio signals? If a launch goes bad and crashes into a liquid mercury ocean, is it just gone? No hope of rescue? I know humans rely mainly and heavily on sight, so it's hard to imagine working without it, and using bat-squeak eco-location instead.