What is the main function of a standalone radar like the SPA-25H?

The SPA-25H is specifically designed for surveillance and tracking purposes, making this option the correct choice. Its primary function is to detect and track various airborne targets, providing real-time information about their position and movement. This capability is crucial for air defense and maritime operations, where situational awareness is essential for decision-making and tactical planning.

In addition to detecting targets, the SPA-25H often integrates with other systems to enhance target identification and monitoring, contributing to effective surveillance. This makes it a valuable asset for military operations that require constant vigilance over airspace or specific geographic regions.

The other options, while related to variant radar and tracking technologies, do not specifically align with the core purpose of the SPA-25H. Flight data recording focuses on capturing flight parameters for analysis, communications relay pertains to facilitating communication between units, and positioning and navigation are more closely associated with systems designed to provide location information rather than tracking targets in the air. Thus, the SPA-25H's distinct function as a surveillance and tracking radar supports its designation in that context.