In air defence operations, radars are vital for detecting hostile targets. On the other hand, stealth technology and ‘electronic counter-measure’ suites that evade or mislead radars have improved the survivability of attacking missions.

Exponential growth in military and weapon related technology has greatly increased the cost and complexity of modern warfare and weapon systems. But for countries which have the necessary resources, there is a vast array of weapon systems to choose from, available in the world markets. Air defence weapons are no exception, as systems tailored to specific requirements can be obtained.

In broad terms, ‘air defence’ (AD) is protection of own airspace, territories and territorial waters against hostile air action both during peace and war. During peace, AD ensures that air activity in the domestic airspace conforms to the laws of the land. During war, AD aims to sustain national will by safeguarding strategic and military capability and preventing hostile air power from inflicting damage to war waging apparatus in own or enemy territory. Such damage could result from attacks by manned aircraft, UAVs or missiles. Pre-emption or destroying enemy air power in enemy territory before it can be employed is termed ‘offensive AD’.

AD is highly time critical due to the speeds at which the aggressor platforms approach targets in own territory. The time available to react could, at best, be a few minutes or even lesser when stand-off weapons are employed. In this short time, the hostile ingress has to be detected, identified, intercepted and destroyed. In the ‘offensive AD’ operations, enemy AD assets have to be suppressed or destroyed to permit own vectors freedom of action in the area of interest.

Radar’s a Must

Thus, in AD operations, radars are vital for detecting hostile targets. The radar could be an airborne interception (AI) radar fitted on a fighter aircraft; a static radar of high or medium power output (with varying detection range and height finding capability); a radar capable of detecting targets at low altitudes; an aerostat radar which is a radar based on a lofted platform; or an Airborne Warning and Control System, which is a radar fitted on a large transport aircraft. Synthetic aperture radars, phased array radars and active electronically scanned array radars are comparatively later additions that benefit from progress in technology, digitisation and miniaturisation. These radars are generally fitted on airborne or space borne platforms and are capable of generating high-resolution imagery.

The IAF’s High Power (HP) and Medium Power (MP) radars are deployed mostly in the western, northern and eastern sectors. The low level transportable radars (LLTRs) on its inventory are also skewed towards these sectors. Consequently, there are gaps in the coverage in other areas. While more LLTRs are on order, there are no published reports of additional acquisition of HPRs and MPRs to plug the existing voids. Integration with civil radars is yet to be operationally realised.

Second operation in the AD sequence is to identify a track on the radar. This is done through a system called Identification Friend or Foe (IFF)—a slight misnomer as the system only identifies a friendly platform which is fitted with compatible and serviceable equipment. Essentially, IFF comprises an ‘interrogator’ and a ‘transponder’. Earlier systems used ‘coded’ radar signals to automatically trigger the transponder in the aircraft being tracked. Modern systems use a separate specialised transponder beacon which can operate without radar. In military aircraft, the IFF transponder responds by returning a coded reply signal only when the incoming interrogation is identified as part of the friendly forces network.

The IFF transponder receives interrogation pulses at one frequency and sends the reply at a different frequency. The IFF is encrypted with a secret key. IFF responders with the same secret key will be able to decode the IFF message and send back a three-pulse reply. The interrogator then compares each reply to the challenge message and marks these targets as ‘friendly’ while also storing their azimuth and range. Thus, the command and control centres can prevent fratricide, gain critical time to counter enemy attacks and retain superior situational awareness while the combat/battle is in progress.

AAM & SAM Systems

Intercepting the target and destroying it are next in the sequence of AD operations. When the warning is sufficient, interceptor aircraft on standby on ground or already airborne can be directed towards the threat. The target is forced to abort mission or, if it continues in the attack, is neutralised by firing an airto- air missile (AAM) or the cannons integral to the fighter aircraft. AAMs are categorised as short range (SRAAMs) and beyond visual range missiles (BVRAAMs), that include long range (LRAAMs) and medium range missiles (MRAAMs). The IAF has both types, acquired from Russia and France. The Pakistan Air Force is in the process of acquiring 500 US advanced medium range missiles (AMRAAMs) AIM-120C5 which are effective up to a range of 120 km.

India is developing the Astra missile with a BVR of 80 km. Guidance of these missiles is either through semi-active or active radar homing or a combination of the two. The capability of the AI radar plays a dominant role in the success or otherwise of these missiles. Short range missiles employed during aerial combat within the visual envelope can also have infra-red guidance system. Some missiles are laser guided. The AAMs are very expensive weapon systems with AIM-120C5 reportedly costing $400,000 (Rs 2 crore) per unit. These also require elaborate environmental protection.

When interceptor aircraft are not available or it is impractical to use them, surface-to-air missile (SAM) systems can be employed. Again, there is a wide variety to choose from. A very special class of SAMs are the anti-ballistic missiles (ABMs) utilised to counter intermediate-range ballistic missiles (IRBMs) and inter-continental ballistic missiles (ICBMs). The threat posed by the IRBMs and ICBMs spurred nations to counter them and the ABM programme was initiated. The ABM system involved continuous surveillance by sets of powerful long range radars and on detection launch of an ABM to destroy the incoming IRBM or ICBM.

Target IRBMS & ICBMS

Exo-atmospheric interceptor missile destroyed the target IRBM/ICBM outside the atmosphere and the endo-atmospheric interceptor did its job after the target had entered the atmosphere. Systems like the US Patriot, Israeli Arrow or the Russian S-300/400 were operational but were not ICBM capable as the ICBM warhead moved much faster than these ABMs.

During the US-Iraq war the success rate of Patriots against Scud missiles was extremely low. Apart from the US, Russia and Israel, India is the only country to have embarked upon an ABM development programme. Late 2006, a Prithvi-2 missile was launched and at an altitude of 50 km it was successfully intercepted by a Prithvi AD interceptor. An endo-atmospheric ABM, the Advanced AD missile, was tested in 2007. Two new systems being developed will be capable of intercepting ICBMs.

An ICBM or IRBM can be destroyed at four different stages: at pre-launch by mounting a first strike; at boost phase, when after lift-off the missile is relatively slow and vulnerable; exo-atmospheric interception, when the ICBM is in space free-flight; or at the re-entry phase. The process is complex and very expensive and as experience indicates, the probability of success is low. If and when India gets a functional ABM system it would be operationalised under the aegis of the Strategic Forces. The low probability of success coupled with extremely high maintenance and carrying costs casts doubts over the cost-effectiveness of India’s ABM programme and the wisdom of continuing with it.