The KM3NeT neutrino telescope has two detectors. ARCA for the detection of high-energy cosmic neutrinos and ORCA for the detection of lower-energy neutrinos. The two detectors are build with the same technology, but differ in the granularity of the light sensor module – or optical modules – and the size of their instrumented  volume.

In ARCA the vertical distance between optical modules is about 40 m. The horizontal distance between the detection units supporting the optical modules is about 100 m. The vertical height of a detection unit is about 700 m. The instrumented volume of ARCA is about 1 cubic kilometer in two ‘building blocks’ of 115 detection units each. ARCA is build at the KM3NeT-It site off the coast of Sicily  at a depth of about 3500 m.

In ORCA the height of the detection units is about 100 m. The vertical distance between optical modules is about 9 m,  while the horizontal distance between detection units is about 20 m. The ORCA detector will have one building block of 115 detection units. In ORCA about 7 Megatonnes of seawater will be instrumented. The detector is build at the KM3NeT-Fr site off shore Toulon, France, at a depth of about 2500 m.