Relocatable Over The Horizon Radar (ROTHR) Deployment in the UK

[JFC Fuller]

Reading Friedman's Fighters over the Fleet I came across the statement that it was planned to install a ROTHR system in Scotland to cover the Norwegian Sea (a statement Friedman has made in several of his books over the years), so I started seeing if I could find out exactly where in Scotland the system was intended to be deployed. However, within the UK I could only find reference to an intended installation in Pembrokeshire, at the south-western tip of Wales. The best available source online is an article in the July 1990 Electronics World Magazine. Key points:

• US/UK project with the UK paying 90% of the £10million development (I think they mean construction) cost, US to pay $90 million for the radar and computer system
• Receiver site and operations centre to be at Brawdy (though the Secretary of state for Defence told Parliament it was St Davids, both St Davids and Brawdy were MOD property until 1992 and are within 7km of each other)
• Transmitter location is not given but is assumed to be over 30 miles way
• Range is at least 1,800miles with an azimuth of 63 degrees focussed on the Baltic
• It would transmit between 2 and 28 MHz at a leak power of 200kw
• The receiver aerial would be 2,590m long and consisting of two rows of 372 supporting poles and 43 equipment shelters
• The locals didn't like the idea

I assume the installation was never built and the plan was abandoned sometime between mid-1990 and 1992. Does anybody have any further information on this? Is Friedman referring to an earlier plan that was abandoned or was it intended to operate two ROTHR systems in the UK, one looking at the Baltic and one at the Norwegian Sea? Or is the claim that the Pembrokeshire facility was to look at the Baltic incorrect?

 

[Yellow Palace]

I assume the installation was never built and the plan was abandoned sometime between mid-1990 and 1992. Does anybody have any further information on this? Is Friedman referring to an earlier plan that was abandoned or was it intended to operate two ROTHR systems in the UK, one looking at the Baltic and one at the Norwegian Sea? Or is the claim that the Pembrokeshire facility was to look at the Baltic incorrect?

According to this record from Hansard, St Davids was to be the transmit site and the receiver to be Blakehill radio station in Wiltshire. Brawdy was explicitly ruled out as unsuitable, along with about 160 other proposed sites. As is normal for proposals to build things anywhere in Britain, there was a lot of opposition. By May 1991 the plans had been cancelled due to cost.

As I understand it, OTH radars aren't really suitable for looking poleward and/or high latitudes, due to interference from the magnetosphere. Presumably this would have put paid to any North Sea proposals. Possibly Scotland was initially floated as the site (there were questions asked in Parliament about OTH radars by the Member for the Western Isles in the early 1980s - this might be a clue) but further development of the proposals made Wales a more suitable site.

This was also around the same time that there were proposals for an ELF transmitter to be built in Scotland (trial site in Glen Garry), so the two projects may have been conflated to some degree.

 

[DWG]

One thought that pops to mind is that a system based in Wales/Wiltshire is somewhat less exposed to attack (on control centre buildings) than one in Scotland. Any attacker has to plough through half of UKADGE to get to it, which might be a worthwhile trade-off vs range.

 

[Grey Havoc]

If I recall correctly, the receivers for the United States' late 1980s USAF (fixed site) OTH radar system had to be at least 50nm from the transmitters. A similar constraint may have applied in this case.

 

[Yellow Palace]

If I recall correctly, the receivers for the United States' late 1980s USAF (fixed site) OTH radar system had to be at least 50nm from the transmitters. A similar constraint may have applied in this case.

30 miles was the planning figure for the US Navy's ROTHR - itself a fixed site system, just one that had been designed to be disassembled, packed into 600 shipping containers, and moved to another site if required.

Perhaps a little off the topic, but a little on ROTHR planned deployment...

After the trial system in Virginia, three production sets were ordered, with an option for a fourth. Proposed sites for these were in Amchitka, Guam, the UK, and Virginia. Ultimate deployment of twelve sets was planned; a second site to cover the Caribbean and Central America was one of these, which ultimately became the Texas site, and the USN's Pacific Command planned for installation of five ROTHR sets to cover the Western Pacific - two in Amchitka and three in Guam. That's still four locations not accounted for - possibly three if the Puerto Rico installation was one of the originally planned sites.

There's a Soviet intelligence assessment on DTIC (unfortunately I didn't bookmark it) that refers to attempts to persuade the French government to allow an installation in the south of France that would cover the western Mediterranean and part of North Africa, which might well be one of them. It would certainly make sense for further installations to be planned to cover the Mediterranean and eastern Atlantic.

The first Amchitka installation took place, using the prototype set, and site selection was under way for the second Amchitka and the first Guam set; the site selection reports give some indication of the technical requirements for the system and sites. Presumably the prototype in Amchitka would have been replaced by a production set in due course if the project had gone ahead. The Guam site selection report specifically identifies that the UK installation would only be one set.

In the course of digging, I've also turned up some interesting stuff on the USAF's fixed-site OTH radars, but that probably warrants a new thread.