Ground-controlled interception (GCI) is a technique whereby one or more radar stations are linked to a command center with communications equipment in order to launch and/or guide aircraft to intercept incoming airborne threats. This technique was pioneered during World War 2 by the British, although the Germans eventually built a successful system also, later in the war. Fighter Command played a pivotal role in the defence of Britain during the war, especially in the Battle of Britain. It is still important today, although nations that can afford it find AWACS, with or without support from GCI, to be more powerful and flexible. This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ... German soldiers at the Battle of Stalingrad World War II was the most extensive and costly armed conflict in the history of the world, involving the great majority of the worlds nations, being fought simultaneously in several major theatres, and costing tens of millions of lives. ... Fighter Command was one of three functional commands that dominated the public perception of the RAF for much of the mid-20th century. ... A major campaign of World War II, the Battle of Britain is the name for the attempt by Germanys Luftwaffe to gain control of British airspace and destroy the Royal Air Force (RAF). ... US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both...

The strengths of GCI are that it can cover far more airspace than AWACS without costing as much and areas that otherwise would be blind-spots for AWACS can be covered by cleverly placed radar stations. AWACS also relies on aircraft which may require deference and a few aircraft are more vulnerable than many ground-based radar stations. If a single AWACS aircraft is shot down or otherwise taken out of the picture, there will be a serious gap in air defence until another can replace it, where in the case of GCI, many radar stations would have to be taken off the air before it became a serious problem (although a strike on the command center(s) could be very serious indeed). US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both... US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both... This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ... US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both...

AWACS tends to be superior in that, being airborne and being able to look down, it can see targets fairly far away at low level, as long as it can pick them out from the ground clutter. A combination of both techniques is really ideal, but GCI is typically only available in the defence of one's homeland, rather than in expeditionary types of battles. US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both...

GCI can also be augmented with the presence of extremely large early warning radar arrays, which could alert GCI to inbound hostile aircraft hours before they arrive, giving enough time to prepare and launch aircraft and set them up for an intercept either using their own radars or with the assistance of regular radar stations once the bogeys approach their coverage. An example of this type of system is Australia's Jindalee over-the-horizon radar. Such radars typically operate by bouncing their signal off layers in the atmosphere.

Either GCI or AWACS can be used to give defending aircraft a major advantage during the actual interception by allowing them to sneak up on enemy aircraft without giving themselves away by using their own radar sets. Typically, to perform an interception by themselves beyond visual range, the aircraft would have to search the sky for intruders with their radars, the energy from which might be noticed by the intruder's Radar warning receiver (RWR) electronics, this alerting the intruders that they may be coming under attack. With GCI or AWACS, the defending aircraft can be vectored to an interception course, perhaps sliding in on the intruder's tail position without being noticed, firing passive homing missiles and then turning away. This greatly increases the defender's chance of success and survival. Alternatively, they could be guided to an interception course and then GCI or AWACS can notify then of the best time to turn their radars on and giving them a vector to the intruders, so that they can get a radar lock and fire their missiles without giving any warning. US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both... This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ... This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ... Typically fitted to military aircraft, radar warning receivers (RWR) detect the radio emmissions of radar systems, whether ground-based or on-board other aircraft. ... Typically fitted to military aircraft, radar warning receivers (RWR) detect the radio emmissions of radar systems, whether ground-based or on-board other aircraft. ... US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both... US Air Force E-3 Sentry AWACS aircraft is prepared for flight in November 1997 Cockpit of RAF E-3 Sentry undergoing upgrades Airborne Warning and Control System (AWACS) is a radar-based electronic system designed to carry out airborne surveillance, and C3 (command, control and communications) functions for both...

During World War 2, airborne radars were so primitive that the defending aircraft needed to close to within what would be easily visual distance during daytime. GCI was often used to vector the defending night fighters very close to the intruders and they then crept up on the often unsuspecting aircraft. GCI and night fighters eventually made night sorties over western europe significantly more risky for bomber crews than they were at the beginning of the war (when they had relative impunity). German soldiers at the Battle of Stalingrad World War II was the most extensive and costly armed conflict in the history of the world, involving the great majority of the worlds nations, being fought simultaneously in several major theatres, and costing tens of millions of lives. ... This long range radar antenna (approximately 40m (130ft) in diameter) rotates on a track to observe activities near the horizon. ... A night fighter is a fighter aircraft adapted for use at night, or in other times of bad visibility. ... A night fighter is a fighter aircraft adapted for use at night, or in other times of bad visibility. ...

More recently, in both the Korea and Vietnam wars the communist forces (North Korea and North Vietnam) had important GCI systems which helped them harass the opposing forces (although in both cases due to the superiority of the U.S. pilots, the effect was eventually minimised). GCI was important to the U.S. and allied forces during these conflicts also, although not so much as for their opponents. Korea (occasionally spelled Corea) is a formerly unified country, situated on the Korean Peninsula in northern East Asia, bordering on China to the west and Russia to the north. ... The Democratic Republic of Vietnam (Vietnamese: Việt Nam Dân Chủ Cộng Hòa), also known as North Vietnam, was founded by Ho Chi Minh and was recognized by China and the USSR in 1950. ...

References

• Radarpages.co.uk GCI page (http://www.radarpages.co.uk/mob/gci/gci.htm)
• Jindalee over-the-horizon radar (http://defence-data.com/features/fpage37.htm)
• [1] (http://www.nzfpm.co.nz/theatres/tow_nfs.htm)