Over three-quarters of all satellites launched are intended for purely military purposes. They relay military radio messages, eavesdrop on radio and radar signals, and take detailed photographs of troop and ship movements, airfields and missiles bases. They can also detect and track enemy missiles, and they help ships and aircraft to navigate, and missiles to find their targets accurately. Russia’s main ASAT system is based on killer satellites, while the USA has concentrated on ASAT missiles. In the future both countries will probably add laser and particle beam weapons to their ASAT arsenals.
The Russian killer satellite system uses a version of the SS-N-9 missile to put an interceptor into orbit that can attack targets in orbit of up to 5,000 km above the ground. The interceptor is put into a lower orbit than the enemy satellite, to allow it to catch up with its target. Once correctly positioned, it fires its engines to boost it into the target’s orbit and then homes in on it, guided by radar or infra-red sensors. As soon as it is close enough, its high-explosive warhead detonates and destroys the target with a hail of shrapnel.
An alternative to using a killer satellite is to knock out enemy satellites with missiles launched either from the ground or from aircraft. Russian may have a ground-launched ASAT missile, developed from the ABM-1 Galosh anti-missile missile, that is capable of destroying satellites in low orbits. The Americans have developed an air-launched missile. The American ASAT missile, launched from a modified McDonnell Douglas F-15 fighter is a two-stage, 5.4 metre-long missile carrying device called a miniature homing vehicle (MHV). To launch the missile, the F-15 accelerates in level flight and then climbs steeply, releasing the missile as it zoom upwards. After the first stage of the missile has burnt out and separated, the MHV continues upwards powered by the second stage and its infra-red sensors search for, and lock on to, the target satellite. In the final phase of the attack, the MHV separates from the second stage and hurtles towards its target. The MHV is only 33 cm long and 30.5 cm in diameter, and it carries no explosive warhead – it simply rams the target to destroy it. But at a collision speed of around 13 km per second, the impact is reckoned to be the same as a direct hit by a 155 mm artillery shell.