HMS Defender returns to the fleet fitted for intelligence gathering

Last week HMS Defender was accepted back into the fleet by Commodore Wood, Commander of the Portsmouth Flotilla after successful completion of post-refit sea trials. HMS Defender deployed to the Gulf for nine months in 2015 after which, she entered an 18-month major refit in Portsmouth conducted by BAE Systems.


HMS Defender is now the described as “the most capable Type 45 in the Fleet.” The main upgrade in capability was the installation of the Shaman communications electronic support measures (CESM) fit to used to gather signals intelligence (SIGINT). The AS-4692 VHF/UHF tapered slotted array direction finding/acquisition array is fitted on the upper part of the pole mast. The AS-4293A VHF/UHF omnidirectional acquisition arrays are fitted half way up the foremast and on the hangar roof. Small HF antennas can be seen mounted on the deck edge amidships, two each port and starboard, just above the retractable companionway ladders.

Shaman is based on the US Navy’s AN/SSQ-130(V) Ship Signal Exploitation Equipment (SSEE) Increment F cryptologic exploitation system. 7 sets have been purchased from the United States at a cost of around $90M and will eventually equip all 6 Type 45s, plus a set for shore-based training. Also included are spares, training packages and support equipment. US personnel were sent to Portsmouth to assist in the initial stages of this sensitive project.

Meeting up with sister ship HMS Diamond during initial sea trails, April 2018

Meeting up with sister ship HMS Diamond during initial sea trials, April 2018. Note the subtle difference between the antenna on the pole masts.

In simple terms, CESM allow the passive interception of adversaries transmissions across a broad part of the electromagnetic spectrum. The system can analyse, geolocate and in some cases may be able to decode encrypted communications. In a naval context, a warship may loiter off a coastline and be able to record signals from mobile phones and military and government radio communications. At sea, intercepts may provide critical detail and forewarning about the actions of adversary’s naval units. It is probable that the communications and capabilities of even our closest allies are also monitored to some extent.

The precise details of this sensitive subject are obviously highly classified but the exploitation of the electromagnetic spectrum by both states and non-state actors is a rapidly evolving art. Continued investment in a broad range of intelligence collection and analysis assets are critical to UK defence. Intelligence gathered at sea may provide part of the picture and be passed to military intelligence agencies and GCHQ that can assess capability and intent by potentially hostile actors.

Installation of Shaman has been slow, a foreign military sales (FMS) license was granted by the US government back in 2011. Its arrival in the fleet finally addresses a significant gap in capability which was lost when the 4 Type 22 frigates were axed in 2010. The Type 22s were equipped with COBLU (Cooperative Outboard Logistics Upgrade) a SIGINT system also jointly developed with the US.

The use of SIGINT in naval warfare is nothing new and goes back to WWI. Interception and decryption of German Enigma traffic played a crucial role in the allied victory of WWII, and in particular during the decisive battle of the Atlantic. In the Cold war, NATO and Soviet warships and submarines made considerable efforts to intercept each other’s communications. Several of the relatively spacious Type 22 frigates were prime platforms for this tasking, being fitted with CESM gear and carrying specialist operators. (Royal Navy submarines are equipped with periscope-mounted ‘Eddystone’ CESM antenna.)


Routine maintenance and repairs were conducted and the ship also received two new gas turbines. HMS Defender has not yet received the major Propulsion Improvement Package (PIP) which is scheduled to begin with the first Type 45 next year. It is relatively easy to change the compressors of Gas Turbine ships which are designed with access routes for their removal for regular refurbishment and replacement. Removing the entire WR-21 Gas Turbine installation itself would be an enormous task and the PIP will instead remove and replace the diesel generator sets. (Full details in an earlier article here) As a newly refitted ship, HMS Defender, along with HMS Dauntless currently refitting, are likely to be the last Type 45s to undergo the PIP at Cammel Lairds yard in Birkenhead. In the meantime, HMS Defender and the other Type 45s are still able to be deployed globally using various temporary fixes and operating restrictions.

The ship is now alongside in Portsmouth for the Summer leave period but will conduct Operational Sea Training, prior to achieving her Fleet date when she will be declared ready for operations.

Damage control and fire-fighting teams take a breather on the flight deck after training exercises during initial sea trials. Note the new VHF/UHF omnidirectional acquisition array on the hangar roof (centre).