On the use of AESA (Active Electronically Scanned Array) Radar and IRST (InfraRed Search&Track) System to Detect and Track Low Observable Threats

The radar has been indisputably the most important sensor in the battlefield, allowing early warning and tracking of air vehicles. Modern fighter ircraft employing AESA fire control radars are able to acquire and track targets at long ranges, in the order of 50 nautical miles or more. However, the proliferation of low observable or stealth technology has contested radar capabilities, reducing their detection / tracking ranges roughly to one third. This degradation is more severe concerning fighter aircraft radars, since most stealth threats are optimised for higher frequency bands, as in the case of fire control radars. Hence, other parts of the electromagnetic spectrum have been reconsidered, such as infrared radiation (IR). Every aircraft is a source of IR, due to fuel combustion, aerodynamic friction and IR reflection. In this way, a jet fighter can be detected by an IR sensor against the cold background of the sky. Therefore, IRST systems have re-emerged, offering an alternative to the radar. Apart from their capabilities concerning target detection (whether stealth or not), IRST systems also exhibit passive operation, resilience to jamming and better angular accuracy. On the other hand, they are prone to weather conditions, especially moisture, while they cannot measure distance directly, as in the case of the radar. This work explores and compares the capabilities and limitations of the two approaches, AESA radars and IRST systems, offering also some insight to the benefits of sensor fusion