I've been through the file again and its obvious things were in a state of flux during this time.
My previous post only touched on the early meetings. I've consolidated everything here.
The First Admiralty/ MoA Working Party Meeting in Feb 1959 discussed the surveillance radar, a four fixed array system (20ft sq each [double-checked, this is correct]) of "very high power". The required performance was to detect a 1m sq target at 125nm at line of sight of 60-70 degrees.
The Fourth Meeting discussed possible launchers and estimated ship sizes.
6,000 tons was the desired size of the ship, with 40-50 missiles. No studies had been made at that time, but it was roughly working out at 8,000 tons and 30ft longer than County at that stage. If no guns were fitted then 2 launchers might fit on 6-7,000 tons.
It was thought the loading blast doors would need to withstand 100 tons loading! Rate of fire was an issue, especially with both launchers aft. The firing arcs were restricted 45 degrees either side of the beam due to likely blast. VLS was considered but would require a bigger ship.
The best launcher, on weight, would be a single-barrel horizontally loaded. The firing interval would be 20 secs per missile. Four illuminators would be carried, three as a minimum fit.
The Working Party even wondered if they should consider separate LA and HA launchers.
The Sixth Meeting in November 1959 had the ship classified as a destroyer of 6,000tons and even possibly as small as 3,000 tons.
The report makes mention of the ASWE Small Ship Surveillance Radar, a scaled down 4 aerial fixed array with inferior performance, no full use of 50+ mile capability, especially in ECM environments.
At the Seventh Meeting in December 1959 the ASWE outlines the radar choices, a fixed 4-array system or the NSR which is described as a scaled down NIGS radar.
At the Eighth Meeting in February 1960 the ASWE outlines the likely radar will be a fixed array frequency scan radar with integral guidance facilities.
A Preliminary Report on a visit to the USA in June 1960 stated the scaled Advanced Weapon System version SPG-59 had specs of 96kW mean power for scanning plus 96kW for illumination, 3,400 elements, 2.5MW power required. In comparison the NIGS system would need four illuminators of 5kW mean power each.
At the Twelfth Meeting (the last one?) the ASWE estimated the radar installation would require 600-800kW electrical power but thought asking for 1MW was advisable. In comparison the US scaled down Advanced Weapon System needed 2.5MW and would be impossible to fit in a 6,000 tons hull. ASWE also said the hull design changes could not be done within the timeframe which suggests some design work must have begun on the ships by mid-1960. However the surveillance radar design had not been chosen at that time, the choices being the FSR or a less ambitious 'fan-beam' type.
The NIGS missile was described as having a homing dish which required less powerful illuminators (which might explain the 5kW power?) and better able to deal with smaller targets than Typhon. However the pencil-beam homing with the RANTEC system just tested in Tartar seemed a possible alternative.
Interestingly, in January 1961 a copy of the NIGS Report was sent to Australia as part of the prep for the delayed Australian Royal Artillery Mission visit to the UK.