“the ship’s radar can see only in the forward 180* has a blind spot aft (I can not confirm this).”
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At least three kinds of radar need to be distinguished from each other, the irdinary navigational radar, the high-power and long-range fire control system that feeds into the ship’s equivalent of the U.S. Navy’s Combat Information Center, and the separate specialized radar transmitter and receiver systems that are built into and physically mounted on the two (I think) “gatling gun” CIWS systems designed to take out incoming missiles that get past all other defensive systems.
The Fire Control radar would identify and track incoming missiles and control all long- and mid-range defensive systems.
I’d be surprised to learn that there would be any azumuthal blind spot at all with respect to the ship’s Fire Control radar. It’s possible that FC radar might have some difficulty distinguishing fast-moving incoming missiles from noise if the missiles are streaking in a few feet over the wavetops. Also, and based on the reports of where missile impact took place this doesn’t appear to be a factor, but shipboard FC radar typically has a blind spot with respect to any missiles coming straight down from directly vertically above the ship. These last two would be “elevational” blind spots.
Ships with fully functional CIWS systems have at least two independent gun mounts that, with their high-speed oscillation onboard radar, “paint” or “patrol” dedicated azimuthal sectors that, when combined, typically afford 360 degree coverage (custom cutouts being built in to prevent the CIWS guns from hitting nearby or adjacent parts of the ship’s own superstructure).
I thought the story of one of her radars having a big blind spot was odd. I have heard stories like that about Russian ships before, and if there is any truth to it Ukraine would know since they built her. So I included the comment with the caveat.
Russian ships typically have more radars and fire control radars than NATO ships. For the Slava, she has six directors for her guns and missiles, and passive electronic surveillance and decoys. Even if she had limits due to construction, age, and dated systems, that is still a lot of radar and weapons for a pair of missiles to get through to hit her.
Her sinking raises a lot of questions about how it happened.