How do infrared-guided missiles such as the Sidewinder track aircraft?

Infrared-guided missiles, such as the AIM-9 Sidewinder, utilize passive guidance systems to track aircraft. These systems do not emit energy; instead, they lock onto the infrared emissions—or heat—generated by the target, typically from jet engine exhausts.12

Early versions of these missiles were restricted to tracking targets from the rear, where engine heat was most concentrated. However, advancements in seeker-head technology have allowed later models to detect exhaust emissions from the side or front of an aircraft. More sophisticated systems can even "see" an infrared image, memorize it using computer logic, and home in on that specific signature.12

Before launch, a human operator or pilot typically confirms a successful lock-on, often indicated by an audible tone in their headset. Once locked, the missile uses its onboard guidance computer and sensors to calculate and maintain an optimal intercept trajectory toward the heat source.2