Ground-based Fire Control and Ground Controlled Interception (FC/GCI) radars work to accurately depict both the target and the ordnance or fighter they are guiding. Military engagement of airborne targets is performed at speed and margins of error make the difference between a kill or miss. Precision is paramount, especially considering that airborne targets may be comparatively small, and the further downrange they are, the smaller the target will seem.
Ground-based FC/GCI radars tend to work closely with other systems like Naval Surveillance or Ground-based Air Surveillance Radars. These radars perform the initial detection of hostile targets. Once these are determined, the targets will be handed over to an FC/GCI radar to manage the engagement.
GCI Radar & FC Radar
Fire Control radar (FC radar) and Ground Controlled Interception radar (GCI radar) have similar functions.
FC Radars are used alongside weapons to help accurately direct fire towards a target.
GCI Radars are used by air defense personnel to help direct a fighter towards its airborne target.
Both radars rely on high levels of precision. This ensures they can bring the ordnance or fighter and their targets together. Although both are integral to air defense, fire control radars can support other tasks. For example, they are integral to a Close-In Weapon System (CIWS) mounted on a warship. CIWSs protect vessels from anti-ship missiles. The CIWS radar will detect the missile as it approaches the ship and maneuver the CIWS gun towards the target. The radar will then monitor the trajectory of the ordnance fired at the missile and continually adjust the gun’s position to ensure the ordnance is on target.
Signal Frequencies & Design Considerations
FC/GCI radars tend to transmit radar signals of comparatively short wavelengths using frequencies of eight gigahertz and above. These signals can depict targets in requisite detail. However, they do so at the expense of range. The higher a radar’s transmission frequency, the lower the range of the signal. This can be ameliorated by increasing transmission power. However, there will come a point where the required power levels will be impractical for the design of the radar. This is because the radar would need to consume large quantities of electricity from the grid or need to be accompanied by a large generator.
Historic use of GCI & Fire Control Radar
FC/GCI radars began to be used en masse during the Second World War. They helped direct searchlights onto hostile aircraft, Anti-Aircraft Artillery (AAA) hit targets and fighters to find enemy aircraft. When assisting AAA these radars were called gun-laying radars. This term was replaced by the fire control radar moniker after the war.
Radar was used for these missions as it was comparatively unaffected by weather and crucially could be used at night. This was an important consideration in the European theatre given the belligerents’ preference for night-time bombing missions. Optronics were in their infancy during the conflict. Sound locators that detected aircraft by the sound of their engines were unreliable. They only worked at comparatively short ranges and lacked the precision to direct fire. Radar, on the other hand, offered hitherto unimaginable levels of precision. This was particularly important considering the pace of air combat. Radar signals travel at the speed of light. Hence, they offer a much quicker way of managing engagements.