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Warships in peril as defence ministry blocks sonar purchase

Ajai Shukla  |  New Delhi 

At the start of this year, INS Vikramaditya, the navy's new aircraft carrier, sailed into the Arabian Sea near the end of a non-stop, 15,000-km voyage from Russia. Accompanied till the Mediterranean by a single Talwar-class frigate, the Vikramaditya was joined by an armada of Indian warships for the last leg of its journey.

This was not celebration, but operational safety. With the navy's best warships worryingly incapable of detecting modern submarines, such as Pakistan's Agosta 90B, the flotilla was tasked to bring Vikramaditya safely home.

The reason for this blindness to submarines: the ministry of defence (MoD) has steadfastly blocked the import of an Advanced Towed Array Sonar (ATAS), a sensor crucial for detecting submarines in warm, shallow waters like those of the Arabian Sea. Without ATAS, India's most advanced warships - including 25 destroyers, frigates and corvettes built and bought since 1997 - would be sitting ducks in any future war. Enemy submarines, lurking undetected, can pick off Indian warships with heavy torpedoes from 50-80 kilometres away.

The import of ATAS was blocked since the mid-1990s because the Defence Research and Development Organisation (DRDO) was developing an indigenous ATAS called Nagan. In 2012, the Nagan project was officially shut down and the DRDO began work on another system called ALTAS. This has not been operationalised either.

Meanwhile, two generations of otherwise capable warships sail with an empty space where ATAS will be fitted some day. Until then, these vessels have only limited sonar capability, provided by a relatively ineffective Passive Towed Array Sonar (PTAS), and a hull-mounted sonar called HUMSA.

The warships without ATAS include three Delhi-class destroyers (INS Delhi, Mumbai and Mysore); three Brahmaputra class frigates (INS Brahmaputra, Betwa and Beas); six Talwar class frigates; and three Shivalik class frigates (INS Shivalik, Satpura and Sahyadri). Ten more warships are currently being built without ATAS - four Kamorta class corvettes (INS Kamorta, Kadmatt, Kiltan and Kavaratti); and three Kolkata class destroyers (INS Kolkata, Kochi and Chennai).

In 2009, responding to a furious navy, the MoD consented to import six ATAS for some Rs 300 crore. A German company, Atlas Elektronik GmbH, won the tender but the contract was stalled by predictable complaints of wrongdoing. After the MoD found four successive complaints baseless, the ministry's independent monitors committee examined the allegations in March. No wrongdoing was found and the committee suggested the purchase be expedited. Yet, Defence Minister A K Antony continues to stonewall.

A serving admiral told Business Standard tersely: "The MoD is endangering warships worth several thousand crore each, and the lives of several hundred crewmen, by blocking the import of ATAS that costs just Rs 50 crore each."

ATAS is especially vital for our neighbourhood. Warships detect underwater objects (like submarines) with sonar - a "ping" of sound emitted into the water that reflects from submarines, just as radar bounces back from aircraft. In our waters, however, that signal often gets lost. Our warm climes cause a sharp "temperature gradient", with warm water on the surface that cools rapidly as one goes deeper. These water layers at different temperatures refract (bend) sonar waves, often deflecting them altogether from the warship's sensors. With the returning sound signal lost, the warship cannot detect the submarine.

To overcome this, an ATAS is towed by the warship with a cable, extending deep below the surface, into the cooler layers where submarines lurk. With the ATAS positioned in the colder water layers, there is no "temperature differential". Even the faintest return signal from a submarine is detected.

PTAS, unlike ATAS, does not actively "ping". It can only detect a submarine that is emitting sound. Since submarines on patrol are deliberately silent, they emit no sound for a PTAS to detect.

While the Arabian Sea offers tricky, shallow-water operating conditions, the Bay of Bengal is much deeper. Thirty kilometres off Karachi, the ocean floor is just 40 metres deep; while five kilometres off Visakhapatnam, the depth is 3,000 metres. The Arabian Sea, therefore, is the playground of small conventional submarines.

Simultaneously, the Bay of Bengal offers the deep diving conditions that favour nuclear submarines, which are too large for shallow waters. That is why experts predict India will operate both conventional and nuclear submarines - conventional in shallow water, and nuclear in deep water. Major navies tend to choose one or the other; e.g. the US Navy operates only nuclear submarines.

In servicing India's need for high-end sonars, the winner of the ATAS tender would grab in pole position. Already, Bharat Electronics Ltd is building 10 ATAS in partnership with a foreign vendor, probably the winner of the ATAS contract. Eighty advanced sonars could be tendered over the next three years.

Besides submarines, sonars would be required for anti-submarine surface vessels. Last month, the MoD tendered for 16 Anti Submarine Warfare Shallow Water Craft. Their critical sensor will be sophisticated sonar with an electronically controlled beam that can flash in any direction.

Notwithstanding the delay in ATAS, Atlas Elektronik is expected to perform strongly, given its expertise in shallow water sonar. Through two world wars, German submarines (called Unterseeboots, or U-boats) were feared for their sonars. During the Cold War, German submarines operated from a short coastline along the Baltic Sea, which was relatively shallow, like the Arabian Sea.

Neither the defence ministry nor Atlas Electronik responded to comments for this article.

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First Published: Fri, May 16 2014. 00:48 IST