Versatile Data Acquisition and Control System for Free-Fall Underwater Vehicles: Exploring Hadal Waters

This article presents the design of a versatile platform based on an Atmega 2560 microcontroller that combines the ability to produce hadal profiles, collect water and biological samples, and provide a moored observation system. When the Lander vehicle moves through the water column, the data acquisition system provides high-resolution hydrographic data. Once the lander reaches the seabed, the system can perform preprogrammed tasks while continuously sampling the instruments at a low frequency to obtain a time series of a few days or up to several weeks. To enhance system autonomy, the platform adaptively modifies the settings of oceanographic instruments during the mission and employs energy-saving techniques. Water samples are collected in the upcast using Niskin bottles, which are closed at specified depths and triggered by a burn wire mechanism. In addition, the platform monitors the electric current of the burn wire circuits to determine the exact closing depth. Advanced instruments, such as a Sea-Bird-CTD FastCAT, an Aanderaa 5331 dissolved oxygen sensor, and a 4K resolution video recording system, are used to study the Atacama trench in Chile, rated to 8081-m depth. The system offers a user interface to set the operational parameters and permits verification that it is properly working. Finally, data obtained from the Atacama Trench are presented, including physical data profiles and biological samples, validating the system design as an effective platform for studying hadal ecosystems.