This is quite simply put, a fleet of satellite telescopes in some kind of sensible orbit that rotate quickly enough to cover a 360 deg band of space, preferably roughly in the direction that doomsday asteroids are most likely to come from given everybody's rotation around the galaxy and our lively jaunt around the sun. Balancing this rotational speed will of course be the minimum time needed to gaze at distant objects to collect enough light to perceive them. Maybe we cover more of the sky this way and have some chance of protection from oumuamua's larger and less friendly relatives, little green men, bored Borg looking for adventure, or even more hostile alien politicians of the latest flavor.
-- RayfordSteele, Mar 01 2019

random, halfbakery