What does 2D search primarily detect?

The primary focus of 2D search is to detect low flying anti-ship missiles. This radar search mode is specifically designed to provide coverage in two dimensions (plan position and range) and is effective in monitoring areas for threats that travel close to the surface of the water. Low flying anti-ship missiles fly at altitudes that can often be obscured by the curvature of the Earth or waves, making them challenging to detect with systems that operate effectively at higher altitudes. The capabilities of 2D search systems allow for tracking these missiles as they approach, providing essential information for timely defensive measures.

In contrast, surface vessels, high altitude aircraft, and sub-surface threats are typically monitored through different search modes or systems designed to handle their specific signatures and operational profiles. Surface vessels might be better detected using various radar methods suited for higher altitude targets, while high altitude aircraft require different radar configurations due to their operational environment. Sub-surface threats, such as submarines, depend on sonar systems for detection rather than radar, which is designed for air and surface targets. Therefore, the emphasis on low flying anti-ship missiles makes it clear why this is the correct answer regarding the primary detection capability of 2D search.