By: TOI

After testing the Agni-III missile last week, Defence Research and Development Organisation (DRDO) is now gearing up for the second test of its fledgling ballistic missile defence (BMD) system. DRDO officials said the BMD system test to be held in May-June will be that of an "endo-atmospheric interceptor missile" this time, on the lines of the US Patriot Advanced Capability-3 (PAC-3) system.

"We intend to shoot down an incoming ballistic missile with the endo-atmospheric missile at about 30-km altitude," said an official.

The first test of the proposed two-tier BMD system took place on November 27 last year when an "exo-atmospheric" hypersonic interceptor missile was used to destroy an incoming Prithvi missile at an altitude of 50-km. The "endo-atmospheric" test is needed since a BMD system to be effective must be capable of targeting hostile missiles both inside (endo) or outside (exo) the Earth's atmosphere.

"The exo-atmospheric interceptor missile was designed by taking Prithvi's propulsion system and adding a second stage to it to ensure it could go up to a height of 90-km," said an official.

"The endo-atmospheric missile, in turn, has been developed to engage targets at about 30-km. After its test, we will test both exo and endo together. The BMD system will have to be tested for a variety of flight envelopes," he added.

That India needs a multi-layered missile defence system with an overlapping network of early-warning sensors, command posts and anti-missile land and sea-based missile batteries to tackle both ballistic and cruise missiles is a no-brainer. Pakistan, for instance, is surging ahead with its 'Ghauri' and 'Shaheen' ballistic missiles as well as the 'Babur' land-attack cruise missile.

It will, however, take at least five years for DRDO's BMD system, or even a medium range surface-to-air missile system (MRSAM), to become operationally ready. India has been discussing missile defence with both US and Israel for the past few years. With the US keen to sell the PAC-3 system to India, the first meeting of Indo-US defence Joint Working Group on April 10 saw the two sides talk missile defence yet again.

Interestingly, the crucial long-range tracking radar used in the "exo-atmospheric" BMD system test was based on two Israeli Green Pine early-warning and fire control radars imported by India in 2001-02. An integral part of the Israeli Arrow-2 BMD system, Green Pine radars can detect incoming missiles up to 500-km away and guide interceptor missiles to them accurately.

A ballistic missile can be targeted at all the three points in its trajectory boost or launch phase, mid-course in space or terminal phase during atmospheric descent. While the PAC-3 system intercepts hostile missiles in the lower atmosphere, the Arrow-2 system destroys them in stratosphere.

DRDO, on its part, is designing the BMD system to intercept an incoming missile at both the "second mid-course and terminal phases", with a "very high" kill probability. "The aim is to first engage in exo and then whatever remains, in endo," the official said.