Now I can't speak for reading source material, but my impression of NIGS is that this is partly a case of parallel evolution and partly the result of sharing ideas and technology (though perhaps we should be talking of theory more than hard systems).
UK theory didn't lag behind the US on computers or radar, but the practical was certainly starting to lag by the late 50's early 60's. Even though the UK had produced hardware/software like Type 984/CDS and fielded it ahead of US efforts at such automation.
This is the period post-Suez and pre-Nassau, so I'm a little hazy on how much was being shared. But raw science was accessible between the two to a greater degree than with any other two states of their kind.
TYPHON was compared and contrasted with NIGS, we've seen that, though quite how accurate the UK evaluation of US systems was and how much access to TYPHON, is another question.
TALOS was considered in place of Sea Slug, the studies are there, but again how much real knowledge did the RN have?
But once again this sort of comparison hits the problems of comparing domestically produced systems purchased in domestic currency with imported systems purchased in foreign currency.
When I dug into solid state emitters for AESA online, I came to one piece by a US university outlining it's history in this field and one of the things that struck me was the evolution of components. Early emitters seem based on garnet crystals and seem limited to S-band or L-band, it's as they develop the components that they can reach up to C-band and then x-band. The latter only into the 1970's.
So let me get this right.....
NIGS radar is larger than NSR
NSR is a scaled down NIGS radar
Feb '59 4 Fixed Array System detection ranges of 125nm for 1sqm, scanning 60-70 degrees. Uses 20sqft arrays
Nov '59 SSSR is a scaled down 4 Fixed Array System with inferior performance and no 50+nm range in ECM enviroments
Dec '59 choice between NSR or 4 Fixed Array System
Feb '60 the ASWE outlines fixed array frequency scan radar with integral guidance facilities. Is this 4 Fixed Array System? And if so, which one? Also is this FSR?
June '60 NIGS uses 4 Illuminators of 5kW power each. Is this the guidance output for FSR?
(date not stated) FSR or less ambitious 'Fan Beam' system. 1MW possible in a 6,000ton hull, US 2.5MW not achievable in such a hull.
Question....if NIGS is using a dish rather than four antenna and mini-dish, this suggests continuing with separate ramjet from the missile body or a rocket based propulsion unit.
Conflicting claims over the use of SIGS type guidance to just dish type guidance.....but this is also a factor of the band in which the illuminators work.
Just thinking about this, Friedman states in "British Destroyers and Frigates" that a June 1959 sketch showed four surveillance radars (it seems safe to assume this means one radar with four arrays), four guidance radars and four illuminators. This is a very similar model to Talos. The later reports suggest the guidance function would be inherent in the surveillance radar though it is not clear whether this means beam riding or command guidance...?
At the very least it shows the NIGS concept evolved though the presence of dedicated illuminators obviously separates the proposed system from the SPS-59 model.
Really should be one 'system', though it would be interesting to know how the phased array radars are integrated together.
Now we know that command guidance for Bloodhound was by a S-band datalink.....and we know S-band is the obvious band for this system....so hypothetically they could do communication to the missile as well as search and track functions.
Whether they could realise this in hardware is questionable, but the theory and software is within reach.
Pulling the illumination function out and keeping it separate would greatly simplify the system....assuming the business of putting the illuminator on the correct target.
Unfortunately the attachments containing the diagrams magazine layouts, the missile launcher, competing solid-fuel and ramjet missile designs and the table comparing the costs of the NIGS missile destroyer with a Typhon armed design have disappeared.