13 August 2025 – Last week we installed a second submarine node for the ORCA neutrino telescope. It is an important step in preparation of the next deployments of detection units for ORCA.
The submarine network of ORCA comprises two long-distance electro-optical cables for communication between the detector and the control station on the shore and a set of submarine nodes, each designed for the connection of up to 24 detection units.
The installation in the deep sea of a node is a complex operation which is executed through close collaboration between ship crews, ROV operators and dedicated KM3NeT teams on board and in the control station.
First the end of the submarine cable was recovered from the seafloor to the deck of the cable ship, where two cable joints were made to connect the node to the cable. Several tests were conducted with the node still on the deck to ensure that the connection was fully functional. Then the deployment of the node started with the cables laid back – to avoid damage the deployment required carefully coordinating the movements of the ship and the lift lowering the node. Finally, the node safely landed on its target position at 2500 m depth within an accuracy of a few meters. Now the node is ready for connection of detection units. Four are already deployed. Up to six more will be deployed in the fall.
The campaign was executed with the “Sophie Germain” cable ship of Orange Marine, equipped with a work-class ROV (Remotely Operated Vehicle) for assisting with inspections and operations on the sea bottom, with the support of the “Opale” vessel of Foselev Marine. The ROV used was a novel vehicle which can be operated either in flying mode or in crawler mode. It was the first time that we used this ROV.
We are very grateful to all offshore and onshore teams for their commitment and careful and precise work.
