PRITHVI DEFENCE VEHICLE (PDV) SUCCESSFULLY TESTED

On February 11, 2017, India successfully tested a Star Wars-type interceptor missile, thus achieving a significant milestone in the development of a two-layered Ballistic Missile Defence system. The interceptor was launched from Abdul Kalam Island (Wheeler Island) off the coast of Odisha. This is DRDO’s latest test towards developing an anti-ballistic missile (ABM) shield, to protect Indian targets against nuclear-tipped ballistic missiles fired from Pakistan or China.

The PDV mission is for engaging a target in the exo-atmosphere region, at an altitude above 50 km. A two-stage target, comprising a new solid-fuelled second stage that sits atop a liquid fuelled Prithvi booster first stage was developed for mimicking a hostile incoming Ballistic Missile launched from a ship anchored in the Bay of Bengal, while the interceptor was launched from Kalam Island. In an automated operation, radar based tracking system detected and tracked the hostile ballistic missile, which was intercepted at 100 km. In the above test, Both, the PDV interceptor and the two-stage target missile, were successfully engaged, putting India in the handful of countries that have this capability, which is now ready for use. This indeed is a watershed moment for India’s ballistic missile defence (BMD) programme.

The test validated the improved guidance algorithm used for mission, since the incoming missile target had deviated significantly from what would have allowed an intercept along a typical minimum energy trajectory (MET) for an ABM interceptor. This indicates the maturity of the on-board imaging infrared seeker (IIR), the responsiveness of the divert and attitude control system (DACT) used by the PDV’s kinetic kill vehicle (KKV), as well as the sensor fusion achieved by various tracking systems involved in the mission.

India’s emerging two-tier ballistic missile defence (BMD) system consists of both endo and exo atmospheric interception capability. DRDO first tested PDV in 2014 in a mission that was essentially used to validate the ABM interceptor’s integration with the detection, tracking and automated launch control systems associated with the two-tier BMD scheme. While no actual intercept was attempted then, the present test was used to prove the KKV used by PDV by destroying an actual incoming warhead in a HTK mission.

The PDV now replaces the PAD ABM interceptor, which was first tested in 2006, as the kill vector in the high-altitude interception leg of the two-tier system conceived under Phase-I of India’s BMD programme. PAD was essentially a high endo-atmospheric system with a ceiling of around 85 km. The PDV however is a true blue exoatmospheric interceptor capable of destroying targets at altitudes of up to 150 km. This puts PDV in a different category in terms of its navigation set-up and homing seeker capability. Instead of sporting a radio frequency (RF) seeker like PAD, PDV uses a strap-down IIR seeker developed by DRDO’s Research Centre Imarat (RCI) with a 128 x 128 focal plane array. Once the development of PDV is successfully complete, it would signal the maturing of Phase-1 of India’s BMD program which is designed to provide credible capability against theatre ballistic missiles (TBM) launched from up to 2000 km away.

The advantage of exoatmospheric interception is that more time is available to direct interceptors towards an incoming target. On the flip side, an interception of a medium range ballistic missile (MRBM) reentry vehicle (RV) outside the Earth’s atmosphere may require that the BMD system distinguish between the re-entry vehicle and decoys, that might be released by the boost vehicle in order to create false targets. The PDV achieves target discrimination in the ‘cold’ of space by using an IIR seeker. PDV’s inertial guidance package that includes a ringlaser gyroscope (RLG) moved its solid-fuelled booster towards the estimated point of interception as calculated by ground-based radars, till such time the KKV was released and its IIR seeker took over in the end game to track the RV. Thereafter, the KKV steered itself continuously to plot a collision course with the incoming RV. In the end, the KKV managed to smash right into the central portion of the RV. The PDV test thus validates the successful integration of the interceptor with DRDO’s proven ground based automated response network that forms the backbone of the two-tier BMD scheme and serves to yet again validate DRDO’s overall BMD C4ISR architecture.

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