Digital compasses for orientation-tilt monitoring in offshore deep-sea infrastructures: the KM3NeT case

KM3NeT is a multipurpose observatory being constructed and operated at the abyss of the Mediterranean Sea, housing two large instrumented/detection networks located 40-100 kilometers off the coasts of Toulon (France) and Sicily (Italy), at depths between 2.4-3.4 kilometers, respectively. The cutting-edge technology implemented in the main calibration systems is pointing to an improved performance in time of KM3NeT. In particular, for high-energy neutrino astrophysics, an angular resolution < 0.05º is expected for the sparser detector if synchronization ~ 1 ns, positioning < 20 cm, and orientation < 3º, for the Detection Units, is guaranteed.

The KM3NeT orientation-tilt system known as “Digital Compasses”, is an Attitude and Heading Reference System (AHRS) board coupled to the inner Central Logic Boards of the Detection Units. The AHRS integrates a 3D-magnetometer containing an Anisotropic Magnetoresistive Sensor (AMS) to estimate Earth’s magnetic field, and an 3D-accelerometer equipped with a Micro Electro-Mechanical System (MEMS) that estimates the acceleration field intensity.

The commissioning and performance (onshore, offshore) of the KM3NeT Digital Compasses, together with the reconstruction of orientation-tilt magnitudes and calibration, will be presented and discussed in this contribution.