[@Flamelord]

Again, Fluff vs OP. Logically speaking I could argue the Imperium merely run constant interference with sensors and communication within their territory, as they use special Voxel systems and Astropaths, both of which are nigh-impossible to block. But yeah, that would stop their own ability to scan. So ima no. Just gonna say the Astronomican 

Let's strike a compromise. You can't move into the Throne City without getting picked out by psykers, cuz they're literally at every entrance. Most military facilities in the Imperium are also guarded by the Grey Knights, as their main task is to protect the Imperium's ground facilities. So Psykers. But you could still sneak into their cities (although luggage would still get checked, similar to airport security. So no carrying suitcase nukes into Imperium territory). 


Considering Cyclonic Missiles are usually shot into the cores of planets, it would probably only destroy about 1/4 or 1/5 of the planet when detonated on the surface. But you get my point, no?