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Evolving radar systems for C-RAM roles in the future

Saurav Jha @SJha1618

Updated: May 29, 2014, 3:12 PM IST
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Insurgent organizations all over the world are looking beyond small arms and shoulder launched weapons that are the usual staple of their arsenals. Middle Eastern groups such as Hezbollah and assorted Iraqi insurgent units have actually graduated to operating long range rockets of different diameters besides increasing the number of smaller tube artillery systems such as mortars at their disposal. It is not surprising therefore that it is in Israel and in US occupied Iraq that the means to counter rocket, artillery, mortar (C-RAM) rounds were first deployed and tested. Although, indirect firepower capability in the hands of terrorists is a concern, the accretion of precision rocket artillery systems by the Chinese is of greater import to India. It is therefore time to closer look at what constitutes the core of C-RAM systems and how the detection and guidance aspects of these technologies have evolved since some of them maybe on offer to India for joint development and production.

While the kill vector used for interception by a C-RAM system could range from a rocket, to a smart 35 mm round, to even a laser, its efficacy depends on its core sensor which is a radar of the phased array variety. Importantly, the radar technology used in C-RAM systems is not specific to it and has grown out of the worldwide trend to combine air defence and counterbattery roles into a single package. This in turn has been facilitated by the maturing of programmable phased array radar technology.

Take the main sensor of the Israeli defence major Rafael's Iron Dome system which has been talked about quite a bit. At the core of an Iron Dome unit is an Elta EL/M-2084 mobile multi-function radar which is a 3D active electronically scanned array (AESA) that can be configured and literally re-sized by adding or removing transmit/receive (t/r) modules for different roles. As such it has two chief modes of operation, one optimized for air defence and the other for the counterbattery role. It is out of the latter that the configuration for the detection and tracking required for C-RAM cueing has been developed. The EL/M-2084 in the counterbattery role tracks about 200 incoming projectiles per minute and has azimuth coverage of 120 degrees and elevation coverage of up to 50 degrees. It can be transported by a C-130 and is naturally capable of remote operation.

Now, counterbattery radar concepts actually go all the way back to the second war but it was only by the 1970s that radars with the ability to truly autonomously detect and plot the trajectory of incoming projectiles could be developed. Once a segment of the trajectory was recorded the radar's processing unit would calculate the location of the firing battery thereby paving the way for a retaliatory response. With the advent of digital phased array radars of decent processing power and compactness that allowed them to be readily deployed on the field many of the problems of older mechanically steered radars were obviated. Phased array radars with sufficient processing capability could detect all radar returning targets in their field of view and could discriminate between them. With AESA technology it was only a matter of time before counterbattery systems could be adapted to C-RAM modes.

Such has been the case with the existing American C-RAM system - Raytheon's Centurion. The centurion is essentially a land based version of the PHALANX close in weapon system networked with the US Army's lightweight counter mortar radar (LCMR) and a Thales Raytheon AN/TPQ-36 fire-finder or its longer ranged cousin the AN/TPQ-37. The LCMR tracks RAM targets in a 360 degree azimuth (which is a first) albeit at much shorter ranges than the AN/TPQ-37 with extended detection ranges up to 50 km away for rockets. The AN/TPQ-36 and AN/TPQ-37 have been standard fare in the US Army for many years now with the latter even being exported to India.

The AN/TPQ-36 and AN/TPQ-37 are however now being replaced by Lockheed Martin's new AN/TPQ-53 quick reaction capability radar in both the counterbattery and C-RAM roles and it is this new radar which will probably work in tandem with the LCMR for future inbound projectile interception systems. The AN/TPQ-53 like its predecessors is also a mobile radar system designed to detect, classify, and track projectiles fired from mortar, artillery, and rocket systems using a 90-degree sector search. It however can also do a 360 degree continuous sector search. This system has updated software which during proving trials supposedly returned a false reporting rate of less than one in twelve hours. These trials check for reporting rates when no actual projectiles are fired towards the radar. The misclassification of aircraft as incoming projectile targets has also seen a significant reduction in the AN/TPQ-53's trials. However unlike the AN/TPQ-36 and 37, the AN/TPQ-53 cannot be transported by a C-130. A C-17 can be used to move the AN/TPQ-53 though.

Meanwhile it seems that Raytheon has been awarded a contract by the US Army to build a prototype Ku Band Multi-Function RF System (MFRFS) Sense and Warn (S&W) radar. This is apparently being developed to supplement existing radars radar integrated with C-RAM systems by helping refine the tracking of the target of interest even further, eliminating false alarms and improving overall coverage. It is noteworthy that this is a Ku band radar since most existing C-RAM radars today operate in the C and S bands. The EL/M-2084, AN/TPQ-36, AN/TPQ-37 and AN/TPQ-53 all operate in the S-band.

First generation counterbattery radars however used to operate in the X-band as that was seen at the time as the most useful part of the spectrum for detecting targets with small radar cross section (rcs). One notable system that follows this older tradition is Rheinmetall Air Defence's (AD's) Modular, Automatic and Network capable Targeting and Interception System (MANTIS) developed under the German Army's Sysfla program for base protection in Afghanistan against RAM threats. The MANTIS is essentially a derivative of Rheinmetall AD's Skyshield 35 mm air defence gun system and therefore uses as its primary fire control system an X-band search and tracking system which works in tandem with a secondary electro-optical sensor both of which are operated by a detached skymaster command and control station that can be located up to half a kilometre away.

Perhaps if the 2009 Ordnance Factory Board(OFB) scandal had not intervened, the MANTIS would have become India's extant C-RAM system given that OFB was all set to license produce the Skyshield. Be that as it may the Indian military today may be seriously looking at bringing in a C-RAM system that is developed by the Defence Research and Development Organization (DRDO) in partnership with a foreign company.

It is significant that DRDO's Electronics and Radar Development Establishment (LRDE) has already developed a counterbattery radar which grew out of the Rajendra passive phased array radar used by the Akash Surface to Air(SAM) missile system. We are of course referring to the Swathi WLR (mentioned above) now produced by Bharat Electronics Limited (BEL) under technology transfer from DRDO. The BEL WLR has performance superior to the AN/TPQ-37(as validated in trials) but operates in the C-band and is a passive electronically scanned array. Besides the BEL WLR, the Indian Airforce has also inducted the Arudra medium power radar which is akin to the EL/M-2084 having been developed with Israeli support and is the first ground based AESA in Indian military service.

These two systems indicate that DRDO clearly has the pedigree to move towards a serious C-RAM system in partnership with the Israelis or some other foreign entity. Such a foreign collaboration could look to build a system that improves upon some of the limitations of current C-RAM systems. Contemporary C-RAM systems are sometimes unable to be effective enough unless positioned strategically to detect projectiles of certain speeds and sizes despite the advances in phased array technology. Moreover even systems like the EL/M-2084 which are touted for their electronic counter counter-measures (ECCM) capability are not impervious to new wireless cyber invasive technologies that ride seemingly standard electronic counter-measures (ECM).

While current generation C-RAMs are perhaps adequate to counter anything Pakistan or its proxies throw at India by way of cheap rocket systems, the real test would be to design effective counter precision guided munition (C-PGM) systems in light of China's acquisition of a large number of precision guided long range rocket systems. These would require longer ranged detection radars as well as interception vectors that can handle manoeuvring RAM systems. Israel's Stunner missile which is part of the David's Sling system comes to mind here. Perhaps something could be derived from the MFCR used as part of India's two-tier ballistic missile defence system.

Follow Saurav Jha on Twitter @SJha1618
First Published: May 29, 2014, 3:12 PM IST

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