Some orbitals have pretty long duration (weather satellites are 60 turns I think). Is there any way to see how long is left? I'd like to build some replacements, ideally so they finish just about when the old ones crash, but I am not really sure how to do find out how long they have left and it's been long enough I don't remember what turn I launched them.
If you know where the satellite is, select it.
If you don't know, open your military overview (F3) find it in that list, and select it.
When you select the satellite unit, the turns remaining is in the unit panel.