You are interested to know how an anti-aircraft missile works. If it is really then I am going to tell you something that would be really very informative for you. I am going to tell you the basics of working of such kind of missiles. They maybe of following types.
1. Radar Guided
2. Infrared Guided
3. Electro Optical
4. Passive Anti-Radiation
1. Radar Guided
Radar guided missiles work on the principle of detecting target's radar signals. They are classified in following ways.
(a) Active radar homing
Active radar (AR)-guided missiles carry their own radar system to detect and track their target. However, the size of the radar antenna is limited by the small diameter of missiles, limiting its range which typically means such missiles have to use two methods to get close to the target before turning their radar set on, often relying on guidance systems.
They have many advantages as well as disadvantages.
Advantages
There are two major advantages to active radar homing:
Because the missile is tracking the target, and the missile is typically going to be much closer to the target than the launching platform during the terminal phase, the tracking can be much more accurate and also have better resistance to ECM. Active radar homing missiles have some of the best kill probabilities, along with missiles employing track-via-missile guidance.
Because the missile is totally autonomous during the terminal phase, the launch platform does not need to have its radar enabled at all during this phase, and in the case of a mobile launching platform like an aircraft, can actually exit the scene or undertake other actions while the missile homes in on its target. This is often referred to as fire-and-forget capability and is a great advantage that modern air-to-air missiles have over their predecessors.
Disadvantages
There are two major disadvantages to active radar homing:
Since the missile has to contain an entire radar transceiver and electronics, it was until recently difficult to fit all of this into a missile without unacceptably increasing its size and weight. Even with today's miniaturisation making this possible, it is quite expensive to make these missiles since the sophisticated electronics within the missile are inevitably destroyed upon impact.
There is very little chance that targets with any sort of decent radar warning receiver would be unaware that an incoming missile is approaching them. This gives them sufficient time to take evasive action and deploy countermeasures. However, given the accuracy of this homing method, unless the target is especially maneuverable or the missile is not, there may not be much they can do to avoid being intercepted.
These types of missiles with this mounted equipment are only effective in long range confrontations.
(b) Semi-active radar homing
Semi-active radar (SAR)-guided missiles are simpler and more common. They function by detecting the radar energy reflected from the target, the radar energy is emitted from the launch aircraft's own radar signal. However, this means the launch aircraft has to maintain a “lock” on the target (keep illuminating the target aircraft with its own radar) until the missile makes the interception, limiting the attacking aircraft's ability to maneuver, which may be necessary should threats to the attacking aircraft appear. It also makes jamming the missile lock easier because the launching aircraft is further from the target than the missile, so the radar signal has to travel further and is greatly attenuated over the distance.
The basic concept of SARH is that since almost all detection and tracking systems consist of a radar system, duplicating this hardware on the missile itself is redundant. In addition, the resolution of a radar is strongly related to the physical size of the antenna, and in the small nose cone of a missile there isn't enough room to provide the sort of accuracy needed for guidance. Instead the larger radar dish on the ground or launch aircraft will provide the needed signal and tracking logic, and the missile simply has to listen to the signal reflected from the target and point itself in the right direction. Additionally, the missile will listen rearward to the launch platform's transmitted signal as a reference, enabling it to avoid some kinds of radar jamming distractions offered by the target.
Contrast this with beam riding systems, in which the radar is pointed at the target and the missile keeps itself centered in the beam by listening to the signal at the rear of the missile body. In the SARH system the missile listens for the reflected signal at the nose, and is still responsible for providing some sort of “lead” guidance. The disadvantages are twofold: One is that a radar signal is “fan shaped”, growing larger, and therefore less accurate, with distance. This means that the beam riding system is not accurate at long ranges, while SARH is largely independent of range and grows more accurate as it approaches the target, or the source of the reflected signal it listens for. Another requirement is that a beam riding system must accurately track the target at high speeds, typically requiring one radar for tracking and another “tighter” beam for guidance. The SARH system needs only one radar set to a wider pattern.
Beam Riding
An early form of radar guidance was “beam-riding” (BR). In this method the attacking aircraft directed a narrow beam of radar energy at the target. The air-to-air missile was launched into the beam where sensors on the aft of the missile controlled the missile, keeping it within the beam. So long as the beam was kept on the target aircraft, the missile would ride the beam until making the interception. While simple in concept, the difficulty of simultaneously keeping the beam solidly on the target (which couldn't be relied upon to cooperate by flying straight and level), continuing to fly one's own aircraft, all the while keeping an eye out for enemy countermeasures, can be readily appreciated.
2. Infrared Guidence
Infrared guided (IR) missiles home on the heat produced by an aircraft. Early infra-red detectors had poor sensitivity, so could only track the hot exhaust pipes of an aircraft. This meant an attacking aircraft had to maneuver to a position behind its target before it could fire an infra-red guided missile. This also limited the range of the missile as the infra-red signature soon become too small to detect with increasing distance and after launch the missile was playing “catch-up” with its target.
More modern infra-red guided missiles can detect the heat of an aircraft's skin, warmed by the friction of airflow, in addition to the fainter heat signature of the engine when the aircraft is seen from the side or head-on. This, combined with greater maneuverability, gives them an “all-aspect” capability, and an attacking aircraft no longer had to be behind its target to fire. Although launching from behind the target increases the probability of a hit, the launching aircraft usually has to be closer to the target in a tail-chase engagement.
An aircraft can defend against infra-red missiles by dropping flares that are hotter than the aircraft, so the missile homes in on the brighter, hotter target. Towed decoys and infra-red jammers can also be used. Some large aircraft and many combat helicopters make use of so called "hot brick" infra-red jammers, typically mounted near the engines. Current research is developing laser devices which can spoof or destroy the guidance systems of infra-red guided missiles.
However, the latest missiles such as the ASRAAM use an “imaging” infra-red seeker which “sees” the target (much like a digital video camera), and can distinguish between an aircraft and a point heat source such as a flare. They also feature a very wide detection angle, so the attacking aircraft does not have to be pointing straight at the target for the missile to lock on. The pilot can use a helmet mounted sight (HMS) and target another aircraft by looking at it, and then firing. This is called “off-boresight” launch. For example, the Russian Su-27 is equipped with an infra-red search and track (IRST) system with laser rangefinder for its HMS-aimed missiles.
In order to maneuver sufficiently from a poor launch angle at short ranges to hit its target, missiles are now employing gas-dynamic flight control methods such as vectored thrust, which allow the missile to start turning “off the rail”, before its motor has accelerated it up to high enough speeds for its small aerodynamic surfaces to be useful.
3. Electro Optical
A recent advancement in missile guidance is electro-optical imaging. The Israeli Python-5 has an electro-optical seeker that scans designated area for targets via optical imaging. Once a target is acquired, the missile will lock-on to it for the kill. Electro-optical seekers can be programmed to target vital area of an aircraft, such as the cockpit. Since it does not depend on the target aircraft's heat signature, it can be used against low-heat targets such as UAV's and cruise missiles.
However clouds can get in the way of electro-optical sensors.
4. Passive Anti-Radiation
Evolving missile guidance designs are converting the anti-radiation missile (ARM) design, pioneered during Vietnam and used to home in against emitting surface-to-air missile (SAM) sites, to an air intercept weapon. Passive missile development is thought to be a countermeasure to low-observable stealth aircraft which typically mount powerful air intercept radars. Due to their dependence on target aircraft radar emissions, passive anti-radiation missiles are primarily limited to forward-aspect intercept geometry.
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