Which of the following is a characteristic of secondary surveillance radar (SSR)?

Secondary surveillance radar (SSR) is a system that enhances the capabilities of traditional radar by using a transponder on an aircraft. This transponder responds to signals from the ground station, allowing for the exchange of information beyond just position and distance. One key characteristic of SSR is that it operates independently of environmental factors that can affect other radar systems.

Because SSR relies on the active participation of the aircraft’s transponder, it is not significantly impacted by weather conditions such as rain, fog, or snow. It also mitigates interference from objects, which can complicate the operation of primary radar systems that depend on the reflection of radio waves from objects. This distinct capability makes SSR particularly valuable in air traffic control and monitoring.

In contrast, the other options highlight characteristics that do not pertain to SSR. For example, being limited to line of sight refers to primary radar systems, which may struggle with range due to obstacles. The reliance on reflected radio waves is also associated with primary radar, while SSR utilizes responses from transponders. Finally, depicting SSR as requiring only ground-based equipment overlooks the necessity of airborne transponders that enable communication and data exchange.