Which sonobuoy is known for its active pings?

The sonobuoy known for its active pings is the RO (Receive Only) sonobuoy. Unlike passive sonobuoys that listen for sounds, the RO sonobuoy does not emit sounds of its own; instead, it is implemented alongside active systems that generate pings in the environment to detect submarines or other underwater objects.

Active pings are generated by an acoustic source that sends sound waves into the water, and the echoes from these sound waves are then analyzed to determine the location and characteristics of the target. This distinct functionality differentiates it from other sonobuoy types.

The other sonobuoys mentioned have different roles: DIFAR (Directional Frequency Analysis and Recording) and ADAR (Advanced Deployable Autonomous Real-time) primarily use passive detection methods, while VLAD (Vertical Line Array Detection) captures sounds but does not employ active pings. The unique purpose and operation of the RO sonobuoy in an active role make it the correct answer in this context.