You’re not the first person to ask me that today.
Air defense systems that use radar all have a “floor” and a “ceiling”. They can’t “see” anything below a certain altitude, and that’s their “floor”. They usually can “see” higher than they can attack (their missiles or guns usually have less range than their radars), so either the maximum altitude it can “see” to or attack to is called their “ceiling”, depending on who’s doing the classifications.
Now, you can have a “soft” floor, or a “hard” floor. A “soft” floor is, as I understand it, a recommendation - that the system may be able to see an attacker below that altitude, but it may not - or its range may be reduced due to the physics and physical limitations of radar. This is the kind of floor most often quoted on US and Western equipment.
On the other hand, Russian radar gear often has a “hard” floor, where the system simply cannot see anything below that altitude. Anything below that floor might as well not exist as far as the radar is concerned. The published “hard floor” for the systems that the Russians sold the Syrians and Iranians is about 500 feet. Which means that you can bring a 20’ tall strike aircraft in at 475 feet, and the thing will never see you coming.
Just like what you hear about in the movies.
Thanks very much for the explanation. I’m familiar with radars on ships - with them you are generally already at the “floor”.