Radars remain the main electromagnetic sensor for all-weather long-range detection and tracking for the army, navy and the air force. High-power solid-state electronics is replacing conventional travelling wave tubes, replacement of rotating radar antennas with steerable solid-state arrays, faster processing and digitisation, smarter algorithms for improving signal processing, reducing clutter and false alarms, multiple-tracking capability and providing contact motion analysis, are some of the main technological advancements which has made the radars a very efficient sensor. The trend is to use solid-state phased array antennae for almost all the frequency bands and use of active multi-function radar systems. Phased array technology permits rapid beam steering capabilities, which in conjunction with an efficient transmitter, receiver and signal processing, can provide almost continuous all-round track-while-scan surveillance capabilities. Synthetic aperture radar (SAR) technology which provides high-resolution three-dimensional imaging capabilitiess has considerably matured over the last three decades.

Future Threat

The air threat includes multiple targets that are stealthy, highly manoeuvrable, supersonic and capable of extremely challenging sea-skimming or ballistic flight trajectories, and attacking under a sophisticated electronic countermeasures environment. Such a threat requires simultaneous multi-function capability, fast response, an extremely large operational bandwidth, matching electronic counter-countermeasures (ECCM) which can take on multiple targets simultaneously.

Multi-function Radars

Navies are planning to change over to the new generation of active phased array multi-function radars (MFRs) for use on ships. Some of the countries like the US, UK, Germany and the Netherlands have already started inducting active array-based MFR technology. Many experts believe that this type of radar will progressively leave more traditional radar systems obsolete in order to meet the emerging threat. Active array is a major turning point in the field of radar technology as it can form a tailor made beam which is software driven, can adapt to different situations and future threats. For example if you want a much higher data rate for missile tracking, it can be achieved. Thus a proper multi-function system can perform five or more functions in parallel.

State of Development

• The US is developing MFR that is meant to equip the service’s next-generation class of DD 21 destroyers with the prime contractor as Raytheon.
• UK is developing Sampson, an E/F-band (S-band) MFR (S-band) MFR with BAE Systems as the prime contractor. Three prototypes and a first-of-class (for a total of eight arrays) have been ordered for the UK Royal Navy.
• The Netherlands, Germany and Canada are developing active phased array radar (APAR), an I/J-band (X-band) MFR of which seven production systems (for a total of 28 active arrays) have been ordered for the navies of Germany and the Netherlands and are now operational. APAR’s prime contractor is Thales-Nederland.

APAR

APAR is a ship-borne MFR developed and manufactured by Thales Nederland. It is the first active electronically scanned array (AESA) MFR employed on an operational warship. APAR has four sensor arrays fixed on a pyramidal structure. Each face consists of 3424 transmit/receive modules operating at X band frequencies. It can operate in a networked mode where it can be used to carry out search by using data transmitted by another sensor. It can carry out missile guidance using interrupted continuous wave illumination technique which can carry out guidance of 32 semi-active radar homing missiles in flight simultaneously, including 16 in the terminal guidance phase. It can also carry out surface gunfire support and has state-of-the-art ECCM. It can carry out tracking of 200 aerial targets at a range of 150 km and 150 surface targets at a range of 32 km. Its horizon search capability is 75 km. APAR’s missile guidance capability supports the evolved sea sparrow missile and the SM-2 Block IIIA missile. To work as an anti-air warfare system (AAWS), APAR is combined with Thales Nederland’s SMART-L radar to provide volume search and tracking up to 480 km. AAWS is based on the NATO anti-air warfare concept of combining two type of radars to optimise their capability. In this case, an X band MFR has been coupled with a L band radar where the L band radar is optimised for long-range detection and tracking of targets, while the MFR is optimised for medium-range high accuracy tracking of targets, as well as horizon search and missile guidance functions. This is an effective concept which is commonly used in any air defence system where there is a separate long-range radar for search and cueing, and a short-range radar for tracking the target. With better technology the combination of two radars can be made more effective. However, there are some who feel that a single system should be designed to carry out all the tasks. APAR is installed on four Royal Netherlands Navy (RNLN) LCF De Zeven Provinciën class frigates and three German Navy F124 Sachsen class frigates. Ships of the RNLN’s De Zeven Provinciën class have been involved in counter-piracy operations off the Horn of Africa. Small slow-moving or even static surface targets can be difficult for doppler radars to detect as they are designed to engage on much faster targets. However, it has been reported that RNLN has used specially made software for search of slower and smaller targets successfully in anti-piracy role.

SAMPSON

Sampson has been evolved from the multi-function electronically scanned array programme which has seen many companies changing hands and finally it was taken over by BAE Systems. The Royal Navy intended to deploy the Sampson MFR on its version of the Horizon Common New Generation Frigate which is a multinational collaboration with France and Italy to produce a new generation of anti-air warfare frigates. Type 45 destroyers use the Sampson radar with the Principal anti-air missile system. As an active array, Sampson uses software to shape and direct its beam allowing several functions to be carried out at once and, through adaptive waveform control, is virtually immune to enemy jamming. Active arrays have both longer range and higher accuracy than conventional radars. It provides search and precision tracking of multiple targets, together with weapon control functions, stealth target detection, variable data rate for threat tracking, high electronic countermeasures immunity and S-band frequency enabling high search rates in clutter.

The Sampson is an AESA radar which uses two planar arrays to provide coverage over only part of the sky and 360 degrees coverage is provided by rotating the arrays. This is in contrast to other systems like the US AN/SPY-1 system or the APAR system, which use multiple arrays fixed in place to provide continuous coverage of the entire sky. The Sampson radar rotates at 30 rpm thus providing almost gap free coverage with a gap of only one second. Sampson also uses smaller number of arrays thus reducing its weight and thus mounting the arrays on a tall mast on the ship whereas in other cases the arrays have to be placed on the side of the superstructure. Arrays placed on higher masts extend their range and improves their low level pickup. BAE Systems state that Sampson eliminates the need for several separate systems. It has a range of 450 km and can track hundreds of targets.

S1850M

S1850M is produced by BAE Systems Integrated System Technologies (formerly AMS UK) and Thales and is a long-range radar for wide area search. It is capable of fully automatic detection and track initiation, and can track up to 1,000 air targets at a range of around 400 km. The S1850M provides 3Dtrack/plot data of the tactical threat and own forces within the operational environment. It has also been selected for the UK’s Queen Elizabeth Class aircraft carriers. It is a modified version of the Thales Nederland signal multi-beam acquisition radar (SMART-L) radar. It is also claimed to be highly capable of detecting stealth targets and is able to detect and track outer atmosphere objects at short-range, making it capable of forming part of a theatre ballistic missile defence system. In all its current applications, the S1850M is the long-range radar component of the principal anti-air missile system. On the Type 45 destroyers it is paired with the Sampson multifunction radar, on the Horizon ships it is paired with the EMPAR multifunction radar.