Which statement distinguishes active guidance from semi-active guidance?

Which statement distinguishes active guidance from semi-active guidance?

• A. Active uses onboard radar to illuminate the target; semi-active relies on external illumination.
• B. Semi-active uses onboard radar; active relies on external illumination.
• C. Both require external illumination and onboard radar.
• D. Both rely on passive emissions.

Answer: (A)

Active guidance means the missile carries its own radar transmitter to illuminate the target and guide itself using that onboard illumination. Semi-active guidance, by contrast, relies on an external illumination source—such as the launch platform’s radar or a separate radar site—and the missile’s seeker just homes in on the reflected energy from that external illumination. This difference in where the illumination comes from is what distinguishes the two methods: active doesn’t need external light to guide, while semi-active depends on it. The other statements clash with how these systems actually work. Semi-active doesn’t use onboard radar to illuminate, so that part is incorrect. It’s not true that both require external illumination and onboard radar, because active uses onboard illumination. And both relying on passive emissions isn’t accurate either, since active emits its own radar energy and semi-active relies on reflected energy from an external source.

Active guidance means the missile carries its own radar transmitter to illuminate the target and guide itself using that onboard illumination. Semi-active guidance, by contrast, relies on an external illumination source—such as the launch platform’s radar or a separate radar site—and the missile’s seeker just homes in on the reflected energy from that external illumination. This difference in where the illumination comes from is what distinguishes the two methods: active doesn’t need external light to guide, while semi-active depends on it.

The other statements clash with how these systems actually work. Semi-active doesn’t use onboard radar to illuminate, so that part is incorrect. It’s not true that both require external illumination and onboard radar, because active uses onboard illumination. And both relying on passive emissions isn’t accurate either, since active emits its own radar energy and semi-active relies on reflected energy from an external source.