## 6 Discussion and Conclusions  
The integration of innovative sensors into existing observing systems significantly contributes to the increase of observational capacity of the platforms and to the provision of new insights for obtaining a more comprehensive picture of the sea state. To this aim, the simultaneous integration of two innovative sensors to monitor underwater radioactivity and ambient sound into the W1-M3A marine observing system was described and first results were presented. Figure 6: (**a**) Counting rate measurements of gamma-rays attributed to the radon progenies \({}^{214}\)Pb and \({}^{214}\)Bi; (**b**) Total detected gamma-rays; (**c**) Rain measured by the rain-gauge on the observatory, the weather radars and estimated by UPAL. In conventional observing platforms, deployment, setting and data management of new sensors is complicated because of the necessary integration with pre-existing scientific payload composed of heterogeneous sensors which operate separately. Furthermore, the installation and efficient long-term operation of underwater sensors on fixed-point observing systems demands compact instrumentation, easy to clamp, low-power consumption and minimum maintenance. As regards the integration of the KATERINA II sensor into the W1-M3A observation system, the spectrum stability was guaranteed by using digital electronics modules adjusting the voltage output of the intense peak of \({}^{40}\)K (at 1461 keV as measured due to the seawater constituents) in the middle of the spectrum (around 512 channel). Long term operation was ensured by the low power consumption of the system (\(\sim\)1 W) and the communication protocol was updated by programming the data-logger to operate via RS232 interface. Also, software functions were developed to achieve communication with the external controller of the observing system. The spectra were analyzed automatically for providing time series of the radon progenies and were transmitted in (near) real-time mode to the operational center. As concerns the sound sensor upgrade, the UPAL sensor uses new low-consumption active filters with better cut-off frequencies, high internal data storage components (up to 128 Gb), and the versatility to be connected to any external power station. Also, for the purpose of integration new low power, low noise, high bandwidth, wide dynamic range combined microcomputer/ microprocessor and ADC, based on FPGA technology capable to accommodate the firmware and the processing smart algorithm were exploited. New solar panels and a wind generator were added to the power supply system of the W1-M3A, and the acquired measurements were included in the data stream of the system to be available adhere in near-real time. The proposed multi-sensor integration can be easily replicated in other observing platforms for long-term monitoring purposes exploiting the capability to deploy the KATERINA II and UPAL sensors as a single instrumental package. In fact, the two innovative sensors can be installed through clamps on different types of infrastructures since the power supply can be either internal (battery pack) or external and both have the capability to communicate with standard protocols (RS232 and USB) in a two-way mode. The operation of both KATERINA II and UPAL can be fully re-configurable through specific commands (i.e., to modify the duration of the acquisition phase for the radioactivity spectrometer, to modify the wake-up intervals for the acoustic sensor, etc.) that have been implemented in the main controller of the hosting platform. The bidirectional communication has been also exploited to retrieve in near real-time a subset of the data acquired by the two sensors. Indeed, a subset of commands have been also coded in a configuration message which can be sent by users to the observatory using the satellite communication system at the end of the periodic data transfer to the receiving station adhere.