Which type of buoys did DICASS buoys replace?

DICASS (Digital Active Controlled Cueing Acoustic System) buoys were developed to enhance the capabilities and functionality of the systems used for underwater acoustics. Specifically, they replaced older RO (research oceanographic) and CASS (Controlled Acoustic Signal System) buoys. These earlier models had limitations in terms of technology and effectiveness; they were not equipped with the advanced features that DICASS provides.

The DICASS buoys are designed for more precise tracking and targeting of submarines and other underwater objects, utilizing active sonar technology. This advancement reflects the Navy's need for improved acoustic signal processing and tracking capabilities, which were not available in the older buoy systems.

In contrast, while passive listening buoys and standard drop buoys serve specific functions in oceanographic research and monitoring, they do not directly relate to the advancements in active sonar technology that DICASS introduces. Therefore, the choice identifying the replacement of older RO and CASS buoys accurately highlights the technological evolution in naval acoustic monitoring and tracking.