OT: the reasoning behind scanners

[Suicide Junkie]

Active scanners are basically like radar...
You send out a pulse of something fast, like photons for example, and watch for the return pulse.

Passive scanners are just really sensitive detectors. The heat spike of engine thrust, the light from windows, the particle emissions of reactors, whatever.

Gravitational detectors could be just a very specialized Version of passive scanners. The tiny disruptions to dust and other objects on the system by a ship's mass would be correlated into a detection.

The rest are more sci-fi...
Psychic could be just telepaths looking for other minds out in space. The cloaking device could provide static-type interference, or bend the psychic energy around the ship like it would for light, etc.

Temporal Make up whatever you want for these... Tachyons, Chronoton detectors, looking at a possible future where the cloaking is accidentally turned off, whatever.