Saw it once at altitude,the tropopause is atmospheric layer that above the air gets really really clear.
Anyway we were high and it was low and we got pretty much best view anybody's going to get of it with the naked eye, we see shooting stars regularly up there but they don't have a flashing beacon like the ISS....sort of gave it away.
Sort of had a 10 second WTF before my FO told me what it was and saved my embarrassment I was just about to call up to have it intercepted!
Good pic.....hugely long exposure ??