Naval radar is a highly technical and sensitive subject but here we provide a basic overview of the world-renowned SAMPSON Multi-Function Radar (MFR) that is integral to the air defence capabilities of the RN’s Type 45 destroyers.
A short history
The UK benefits from a legacy of expertise in radar, having led the world in pioneering its development during WWII. The technical foundations of the SAMPSON radar pre-date the Type 45 destroyers considerably and by the time the last unit was manufactured, represented the culmination of nearly 30 years of research and development.
The MESAR (Multi-function Electronically Scanned Adaptive Radar) programme was a technology demonstrator started in 1982 as a partnership between the MoD (DERA), Roke Manor Research and Plessey. MESAR-1 was an S-band prototype active array multifunction radar which was developed between 1989-1995. This was revolutionary, being the first example of a radar the combined Transmit/Recieve (TxRx) modules and anti-jamming digital adaptive beamforming techniques.
MESAR-2 was in development from 1995 and tested between 1999-2001 employing a new antenna design, a new T/R-module and featuring microwave solid-state power amplification and phase shifting. MESAR-2 was primarily intended to explore Ballistic Missile Defence capability and detection of low-level targets over sea and land. MESAR was never intended for production but SAMPSON built on much of the architecture they had pioneered, including gallium arsenide (GaAs) semiconductors, multiple low power modules and air cooling.
Radar was of the many reasons the UK left the Horizon frigate project in 1999 (an attempt to develop a common air defence warship with France and Italy). Needing genuine area air defence capability for its aircraft carrier group, the RN had much higher demands for long-range coverage. The Europeans planned to use the less capable EMPAR system, refusing the ‘not invented here’ SAMPSON option.
A series of mergers and take-overs through the years meant the SAMPSON project was owned by several different corporate entities through its development and manufacture. Some design work on SAMPSON, an operational derivative of the MESAR, was initiated in 1989, although not made public until 1991. Siemens-Plessy hoped it would be ready by 1994 but progress was slow, no prototype was made and MESAR-2 took priority. Plessy was taken over by a BAE Systems joint venture with Finmeccanica called Alenia Marconi Systems in 1998. This was subsequently dissolved and taken over by BAE Systems Integrated System Technologies (BAES Insyte). Insyte was merged into BAES naval business in 2010.
The first three Type 45 destroyers were ordered in November 1999 and by September 2002, BAES Insyte had completed a dedicated SAMPSON test facility at their Cowes site on the Isle of Wight. The first transmission from a SAMPSON unit was made in March 2004 while the first prototype (P1) was fitted to a representative Type 45 foremast later that year. P1 completed testing in June 2006 and was transferred to the Eskmeals range in Cumbria for further trials and integration work.
In 2006 the second prototype (P2) was fitted to the Longbow barge for Aster missile live-firing trials which took place in late 2007. A third prototype (P3) was installed at the Maritime Integration and Support Center (MISC) at Portsdown hill in 2006. HMS Daring was fitted with the first production radar in April 2007 at the shipyard in Scotstoun and manufacture of the final unit for HMS Duncan was completed in July 2011.
Antenna and mast
The distinctive SAMPSON antenna is mounted in a single carbon-fibre composite frame which holds two hexagonal back-to-back planar arrays. Two semi-circular radomes cover the arrays to complete the ball shape which is about 4.8 meters in diameter. At first glance, antenna appears spherical but when seen rotating it is obvious that it is not symmetrical in all axis and tapers at the sides. Mounted on circular, highly durable race and roller bearing designed to cope with temperature extremes, the antenna is rotated at 30rpm. The 4 “whiskers” protruding from its surface are designed to conduct lightning strikes away from the sensitive array.
Keeping the arrays relatively small and using lightweight mounting materials, combined with the wide (21.2-meter) beam of the ship, allows the antenna can be placed 10 decks above the main upper deck. At almost 40 meters above the waterline, this is nearly double the height of the fixed arrays of the US Arleigh Burke destroyer’s AEGIS system and greatly increases the ship’s radar horizon and therefore warning of sea-skimming threats.
The 19-meter foremast is a complex piece of engineering in itself and they were built by Vosper Thornycroft in Portsmouth before being delivered by barge to Glasgow for mounting on the ships. The mast includes 800 separate cables totalling 12,000m for the radar, RESM and communications ariels and a further 400m of pipework.
Since SAMPSON works on low voltage and relatively low power (25kW), the antenna is air-cooled, avoiding the complex liquid cooling systems used by many legacy radars. An air conditioning unit one deck below the antenna produces chilled air which is driven by fans up into the void between the two array faces and then forced through small holes in the TR module covers directly on the elements to be cooled.
The all-seeing eye
SAMPSON is designed to operate in very demanding environments to counter stealthy supersonic and highly manoeuvrable missile or aircraft targets that may follow sea-skimming or ballistic flight profiles. Multi-Function Radars can perform search, tracking and fire control simultaneously using many channels. SAMPSON electronic counter-countermeasures (ECCM) include pulse-compression and frequency agility making it virtually immune jamming. As an active array, the radar beams are software-driven and can switch between hundreds of channels and waveforms, each optimised for certain search angles, from wide-area searching to focussed high-data rates for missile tracking. The increase in the capabilities of MFR compared with conventional radars was arguably the biggest technological advance the introduction of the Type 45 made over the Type 42.
For Sea Viper missile guidance, SAMPSON is especially effective because it can detect stealth targets at long range and initiate tracking instantly. Operating in the S-Band between 2 – 4GHz, SAMPSON surpasses conventional ultra-high frequency (UHF) and super-high frequency (SHF) systems. The field of view is hemispherical up to the zenith position and including directly overhead. The two arrays have a 120º field of view but by rotating them and using steerable beams, complete 360º coverage is maintained at all times.
The high definition can provide target size estimation and non-cooperative target recognition. Officially SAMPSON can guide up to 16 Sea Viper missiles in flight and track about 1,000 separate targets simultaneously. Maximum detection range is at least 250 miles (400km) and up to the edge of the outer atmosphere. The marketing blurb for public consumption says “SAMPSON can track 1,000 objects the size of a cricket ball travelling at Mach 3” and this is not an unreasonable claim.
SAMPSON has all the advantages that come with using Active Electronically Scanned Arrays (AESA). The EMPAR and the Type 45’s secondary TS1850M radar are passive (PESA) systems that use a single signal and frequency emitted by multiple separate elements. While excelling at long-range general search they lack the same level of precision, are typically heavier and present a greater cooling challenge. Not only is AESA more precise and resistant to jamming, but is more robust, if one of the 640 SAMPSON TR modules in each array fails, the system continues to function. Failed modules can be replaced via access to the back of the array and an automated calibration system facilitates rapid return to full operating condition after replacement.
Although the antenna is the most readily identifiable part of any radar, the computers, software and control equipment below decks are every bit as important. US company, Mercury Computer Systems, provide the commercial-off-the-shelf RACE processors that perform signal processing which shape and point the beams instantaneously in any direction and in real-time. The vast amounts of data received back from the sensor also require complex software to analyse, compile and present a usable picture to the warfare specialists in the operations room. Tessella UK was involved in mathematical modelling to develop the integrated set of automated tracking algorithms and innovative output graphics to facilitate data analysis. The system uses fibre-optic cabling and a high-speed data link in excess of 20 Gbits/s.
In many ways, SAMPSON is a microcosm of all that is good and bad about UK defence procurement. Probably the best sensor of its type in the world it was developed by some of the finest British engineers who overcame incredible technical hurdles. When HMS Queen Elizabeth sails on her first operational deployment in 2021, the RN will have very high confidence in the air-defence protection afforded by the two accompanying Type 45s.
Sadly much of SAMPSON’s potential has been squandered and the edge it gives to the RN has spread too thin, with just 6 production and 3 prototype units manufactured. Halving the number of Type 45 destroyers effectively doubled the development cost per unit of the whole programme, including the radar. SAMPSON was considered for fitting to the QEC aircraft carriers but deleted at an early stage as a cost-saving measure and no export orders have been forthcoming.
SAMPSON is by no means a development dead-end and BAES considered multi-face versions with three, four and even five arrays, including a zenith array looking straight up for BMD use. A simplified, reduced-cost vision with a single array called SPECTAR was also being offered for export. At least the more affordable medium-range ARTISAN 3D (Advanced Radar Target Indication Situational Awareness and Navigation) which replaced the Type 996 in RN service was developed rapidly using some of the technology derived from SAMPSON.
SAMPSON has inherent capability to detect ballistic missiles. In September 2013 HMS Daring participated in a BMD demonstration led by the US Navy. She detected and tracked two medium-range ballistic missile (MRBM) targets at the Reagan Test Site in the Pacific, surpassing expectations. Unfortunately, there is little funding available for the RN to significantly continue this line of development or acquire ABM-capable missiles for the Type 45.
After a decade in service, SAMPSON has not received any significant upgrades. This is maybe a testament to their original excellence as much as funding limitations. In Oct 2018 BAE Systems said it was considering potential development options. The MoD said in March 2020 that no upgrades to SAMPSON have been made but the routine overhaul of the systems in service costs about £400k annually.