Missile Defence and Early Warning Systems

Ahmed Ijaz Malik

The missile proliferation has complicated the nuclear strategic scenario worldwide. Missiles are a mode of launching nuclear warheads and have sensitive launching mechanisms. These mechanisms can have complications. The launching arsenals and systems combined to the missiles are by their mechanical build up capable of causing misperceptions or false signals. The missile capable states, especially the states locked in conflicts, must have a system where the probable launch intentions of the adversary can be known before hand or at least at the time of forward deployment. The Early Warning Systems can be helpful in such circumstances. They can be a mode of removing any misperceptions that can lead to a nuclear launch or a counter strike.
To adequately define and understand the Early warning systems there is a need to have a clear understanding and advanced knowledge of the nuclear arsenals and the weapons. The concept of warning has been diversified by the advent of new circumstances, where a nuclear missile can be launched due to the misperception or the complications existing in the launching system itself; capable of causing errors. There can also be situations where there is a coup and the weapons fall in the hands of irrational individuals, or a region having nuclear installations, declares independence and decides to use nuclear weapons against its adversary, or the extreme possibility of a computer hacker being able to break in to a system and give a false signal to one of the parties in crisis. There is an idea of a bolt-out-of-the-blue nuclear missile attack, where a country faces an unexpected and unforeseen, but deliberate attack. In such a situation there technically, is no responding time even in the cases where the strategic warning time is between twenty five to forty minutes.

The early warning systems include the radars, sensors and strategic photo-reconnaissance with aircraft like SR-71 or the U2, which act for surveillance and provide information of a missile launch. These systems work together with the retaliatory response mechanisms. The incoming warhead is detected and tracked by some combination of radars. The information obtained by the radars is interpreted and processed by sophisticated computer facilities. The destruction of incoming warhead is accomplished by an interceptor (missile) warhead exploding in the vicinity of the incoming warhead. The sheer magnitude of the task, intercepting an enemy warhead traveling at four miles per second with an interceptor traveling much more slowly, seemed to give meaning to the metaphor of " hitting a bullet with a bullet", as quoted by William Schneider Jr. in "Missile defence systems: Past, Present and future".

The concept of Early Warning is understood when the targets, missiles and the surveillance systems are collectively studied. The nuclear delivery force currently consists of a triad of three weapons systems: long-range bombers with nuclear air-to-surface missiles, ICBMs and SLBMs launched from nuclear-powered submarines. The defense of this force is more complex and consists almost entirely of passive defense systems designed to provide early warning of a missile strike, as well as to protect missiles by concealing them on submarines, dispersing them on mobile launchers, or fortifying them in underground silos.

The targets are identified and categorised according to their significance to the command and control. In its ideal form a ballistic missile launched is identified by the space or ground based surveillance and monitoring system. The velocity and direction along with the heat signature of the incoming ballistic missile warhead is assessed and the information is sent to a computer system. This system in connected to the interceptor missile launching system and the incoming ballistic missile is targeted on the basis of the information collected. The ballistic missile launched goes through a boost, entry and a reentry phase. It can be targeted when in the reentry phase because it has reached a certain specific velocity and direction and the decoys attached to it (to misguide the interceptor missile) have been detached. Moreover the ballistic missile now has a specific heat signature, which is the amount of heat it emits, making it easier to be identified by the interceptor missile; that are usually heat-seeking missiles in nature. The interceptor missiles usually consist of exoatmospheric kill vehicles that have infrared sensors. As the name signifies these interceptors are meant to destroy the ballistic warheads in the outer atmosphere.

North American Aerospace Defense Command (NORAD) employed a variety of means to monitor the strategic missile forces of the Soviet Union, which at one point in the mid-1980s consisted of 1398 ICBMs (Intercontinental Ballistic Missiles) and 983 SLBMs (Submarine Launched Ballistic Missiles). The detection and tracking devices installed by NORAD include radar and sonar; laser beams; high-resolution optical devices using natural or artificial illumination; and magnetic, thermal, chemical, and acoustical sensors. This equipment may be located on ground, on sea, on airplanes, or on space satellites, and, when linked together by a central control for a specific set of tasks, it constitutes a defensive system. The most important of these systems is the Ballistic Missile Early Warning System (BMEWS), a complex of warning and tracking radars based at sites in Alaska, Greenland, and the United Kingdom. This equipment can detect a missile as far as 4800 km (about 3000 miles) away and provide a 15-minute warning of an attack on North America. BMEWS is backed up by the Perimeter Acquisition Radar Characterization System (PARCS), formerly the tracking unit of the phased-out Safeguard ballistic missile defense system. Operating in the U.S. interior, PARCS is powerful and precise enough to tell how many warheads are arriving and their specific impact areas. Warning of SLBM launches is provided by radar systems using phased-array antennas located along the Atlantic, Pacific, Alaskan, and Gulf coasts. This setup replaced the old SAGE (semiautomatic ground environment) air defense radars. In addition, early warning satellites are used to sense missile launches and aid in tracking trajectories.

There are three kinds of targets categories for ballistic missiles.The first target category consists of ICBMs either in hardened silos or on some sort of mobile or deceptively based deployment systems.The second type of targets consists of command, control and communication (C3) facilities and other military targets (OMT)-Air bases, Nuclear powered ballistic missile submarine bases (SSBN), intermediate nuclear INF, areas and storage facilities, garrison areas protected by a non-nuclear kill vehicle. The third target categories consist of population and cities.

The defence systems are basically on the nature of interceptor missiles. The BMD systems that could be developed to defend these three targets sets are drawn from wide range of technologies, encompassing different capabilities. Wolfram F Hamreider in the book 'Global peace and security trends and challenges' has presented seven mechanisms of missile defence. Firstly there is a Traditional endoatmospheric defence consists of radars and interceptor missiles designed to destroy Reentry Vehicles (RVs) in the atmosphere, relatively close to the targets being defended. Secondly there is Traditional exoatmospheric defence consists of radars and long-range interceptor missiles designed to destroy incoming RVs outside the atmosphere (or at a great distance and altitude) and can be used either to cover a large area with a single defensive battery or to augment an endoatmospheric BMD by providing an extra layer (or level of defence). In this system, nonnuclear kill mechanism are used a combination of very large (and vulnerable) radars and infra red (optical) sensors for guidance, target acquisition and RV/decoy discrimination. Such a system has some utility in defence of "soft" fixed targets. Third Simple-novel systems, designed for the terminal defence of hard targets such as ICBM silos, use relatively unsophisticated technology to "spread a curtain of projectiles in the path of an attacking warhead during the final seconds before the arrival at the target". A simple radar is required, and the kill mechanism involved range from multiple unguided rocket launchers (Swarmjets) to Gatling guns, large fragmentation warheads, and-in the more sophisticated variants-missiles with homing seekers. Fourth, the Dust defence consists of an arc of high-yield nuclear weapons buried in the ground some distance north of the ICBM silos that they are to defend (under the likely reentry path of incoming RVs). After positive warning of an attack, and five or ten minutes before the arrival of the first adversary RV, the buried devices are detonated. The resulting clouds of dust and debris rise to high altitudes in the path of the incoming RVs, ablating each RVs heat shield and causing either the warhead's destruction or a severe degradation of its accuracy. Fifth there is Nontraditional terminal or area defence, which involves the use of ground-based, or air based directed energy weapons to intercept RVs during their reentry. Sixthly, the Advanced midcourse overlay defence employs infra red homing devices, either space based or launched abroad ICBMs or SLBMs, to intercept individual RVs in midcourse before reentry, usually using some sort of nonnuclear kill mechanism. Seven, there is an Advanced boost phase/ post boost defence consists of orbiting, space based battle stations and use projectiles, chemical lasers, excimer lasers,x-ray lasers or particle beams to intercept ballistic missile second stages and post boost vehicles before individual RVs have been dispensed.

The modern system of missile defence is Theater High Altitude Area Defense (THAAD), an aggressive initiative to field the first endo/exoatmospheric system for defense against Theater Ballistic Missiles (TBM). Theatre Ballistic Missile Defence is a system of defence relavant to a limited area. Theater High Altitude Area Defense is the recent trend in missile defence systems. The US program for a NMD is a continuation of this idea of defence. THAAD's design calls for the 'Kill Vehicle' to intercept and destroy its target using only the kinetic energy of a direct hit. Its effectiveness depends on its ability to physically destroy the target. This ability is referred to as lethality. THAAD will provide the most lethal upper-tier, hit-to-kill intercepts across a range of threat types by optimizing mass and engagement conditions. THAAD lethality sled tests and high-velocity subscale testing are demonstrating lethality performance for representative engagement conditions.

Among THAAD's unique set of attributes is the fact that it is designed to exploit commonality with other Army equipment. For instance, the launcher is based on the U.S. Army Palletized Load System and the BM/C4I shelters are mounted on High Mobility Multi-purpose Wheeled Vehicles (HMMWVs). THAAD generators, computers, communications equipment, and Global Positioning System receivers are all standard Army equipment. Furthermore, the THAAD weapon system is transportable by C-130, C-141 and C-5 aircraft.

In recent developments in missile defence, the theatre missile defence as been up dated. In Tuscon, Arizona, US scientists are crafting 140-cm long, 55 kg missile killers. These "exoatmospheric kill vehicles" are designed to smash invading weapons 225 km above the earth's surface, long before they can reach a US city and kill thousands, if not millions. The US space shield satellites would detect the launch of an enemy missile and cue ground-based radars to find it. Data on its path would be downloaded into the interceptor before their launch from the main land Alaska bases, with update radioed to them in flight. Four interceptors fired two at a time, would be dedicated to each incoming warhead. If the first pair should miss another would be fired.

The modern system of missile defence works in four phases. The US spy satellite in orbit detects an enemy missile launch. An X-band radar in the Aleutian Islands tracks the path of the incoming missile, distinguishing a real warhead from from its decoys. The Battle Management center in Colorado hands of the radar data to the fleet of interceptor missiles in Alaska. The exoatmospheric kill vehicle separates and, using infrared sensors, guides itself in to enemy missile destroying it 140 miles (225 km) above the earth. In fact, there is concern that the new and more powerful booster-which will shake the kill vehicle ten times as hard as the test booster now being used-could damage its own optics or electronics and render the interceptor powerless.

The tests conducted so far, have still not been completely successful. The second in January 2000, missed by about 130 m when a "few molecules" of water froze in side a cooling pipe 0.09 mm in diameter-the width of human hair-and shut down the interceptor's heat seeking sensors. The latest test conducted on the 14th of July has been successful but the skeptics have their doubts about these mechanisms guaranteeing a complete defence against a massive missile attack.

Early warning systems are a prerequisite of missile capability. The rational consideration is the need for acquiring early warning capabilities. The early warning systems and mutual cooperative monitoring can also guarantee the prevention against provocative actions, by ensuring exchange of verifiable and authentic information. It is essential that the countries having history of conflict buildup their early warning capabilities to monitor their adversaries deployed missile sight during crises and to prevent any inadvertent, miscalculated or misperceived missile launch.