MEDUSA system consists of four buoys, elastic beacon type, installed in the Gulf of Pozzuoli at a
distance from the coast line ranging from 1.1 to 2.4 km and at depths ranging from 40 to 100 m.
Each buoy is connected by a cable to a seafloor module equipped with geophysical and oceanographic sensors and kept few meters apart from the buoy ballast.
Each module includes:
- 3-component broadband seismic sensor (Trillium Compact OBS)
- 2 low-frequency omnidirectional hydrophones
- 3-component accelerometer (MEMS technology)
- bottom pressure recorder (Paroscientific pressure sensor)
- Titanium vessel with:
- 2 high resolution acquisition systems (Kinemetrics-Quanterra Q330 and Guralp-DM24S3)
- status and control sensors and electronics.
Power supply, data transmission and clock signal are ensured to the module equipments by an armored electro-mechanical cable, also used for the module handling and installation/recovery.
On the top of the buoy, a turret hosts the power supply system (solar panels and buffer batteries), data transmission and control electronics.. Real time data transmission to the Osservatorio Vesuviano monitoring center is achieved by a WI-FI device at 5 GHz.
One of the four buoys is equipped with a meteorological station (temperature, humidity, atmospheric pressure, wind direction and speed).
Moreover, each buoy is equipped with a passive radar reflector and a self-powered lamp with a crepuscular switch with blinking.
Differently from the standard floating monitoring buoys, anchored on the seabed by a cable and free to move driven by the sea level changes and water currents,
MEDUSA special buoys are not affected by sea level variations.
The buoy has an underwater float, located a few meters below the sea level and made with polyurethane foam. A pole supporting a top turret is inserted into the float and hooked to the concrete anchor on the sea floor. This mechanical solution adopting a long pole has been conceived for the two buoys (CFB1 and CFB3) deployed at a sea depth of about 40 m.
For the other two buoys (CUMAS prototype and CFB2), operating at depth of about 96 and 75 m respectively, being a sole long pole impracticable,
a steel cable links the pole to the ballast on the sea bottom. The cable is kept in tension by the float which provides a buoyancy of about 7 tons acting on the ballast,
which has a mass of about 14 tons. In this way each buoy represents a system rigidly coupled to the seafloor. Consequently any vertical movement of the seafloor propagates
to the emerged part of the buoy itself, allowing measurement of the vertical movement.
For this reason each buoy was also equipped with a GPS station on the top.