Integration of the ahoi Modem into the MOLA Seafloor Lander System: Concept, Realization and Real-World Trials

Seafloor landers are used for various marine research and exploration applications. Most available ocean landers are large, heavy and expensive, and their operation requires vessels with heavyduty cranes for deployment and recovery. We present the Modular Ocean LAnder (MOLA), a small and low-cost ocean lander system, which integrates an ahoi modem to enable low-cost underwater acoustic communication. We first describe the hardware and software integration of the ahoi modem in the MOLA system. Due to the limited operation depth of the ahoi modem’s default transducer, we explore alternative transducers with different specifications for the system. We present the results of a real-world, deep-sea evaluation of our system offshore Sicily in the Mediterranean Sea. Using transducers with appropriate depth ratings, we achieved stable vertical communication links up to 1000m depth. Furthermore, we deployed a network of three MOLAs at 165m to 185m depth on the seafloor. The communication link was stable for most communication baselines and we successfully triggered the release mechanism for coming up with an acoustic packet and recovered all MOLAs. Finally, we outline the next steps of our development.