64PE367 - Introduction

KM3NeT
KM3NeT, a European deep-sea research infrastructure, will host a neutrino telescope (NeT) with a volume of at least one cubic kilometer (KM3) at the bottom of the Mediterranean Sea that will open a new window on the Universe. The telescope will search for neutrinos from distant astrophysical sources like gamma ray bursters, supernovae or colliding stars and will be a powerful tool in the search for dark matter in the Universe. An array of thousands of optical sensors will detect the faint light in the deep sea from charged particles originating from collisions of the neutrinos and the Earth. The facility will also house instrumentation from Earth and marine sciences for long term and on-line monitoring of the deep sea environment and the sea bottom at depths of several kilometers. Presently, about 40 MEuro is available from various national funds to start construction. The NWO investment programme for large European Structures has granted Nikhef-Amsterdam, NIOZ-Texel and KVI-Groningen 8.8 MEuro to set-up the dutch part of KM3NeT. Eventually, 150-250 MEuro is needed to build the entire telescope. Proposed sites are in the Northern Hemisphere, to compliment the IceCube-telescope in Antarctica. The sites are all in the Mediterranean Sea where sufficiently deep (below 1500 m) waters are found within several tens of kilometers from coasts. This facilitates the huge data transport to shore. Three sites are selected: ANTARES near Toulon France, NEMO east of Sicily Italy, NESTOR west of Peloponessos Greece.

KM3NeT13 cruise
The purpose of the KM3NeT13 cruise in the Alboran Sea (south-Spain) is to perform multiple test-deployments of a single string of 700 m high holding 17 optical modules with data communication cable. Each deployment test will be followed visual under-water inspection of the mooring by ROV. Some environmental conditions measurements on temperature and current variations will be conducted simultaneously for proper interpretation of the mooring tests. A temporary land-station will be built at the quay-side in the harbour of Motril to remount the 'compacted mooring launcher'.

Compacted mooring
NIOZ/Nikhef built a compacted string-mooring, to deploy 18 glass spheres with optical modules (sensitive light sensors). In total about 600 strings are to be deployed. The entire 690 m string and top-buoyancy will be mounted in and on a 2.1 m diameter aluminium sphere, the Launcher of Optical Modules (LOM). This LOM will be mounted directly above a bottom-weight. Upon acoustic release it will unroll its lines within 10 minutes and release the optical modules due to its positive buoyancy. After releasing the top-buoy it will detach itself and surface freely, together with its acoustic release-buoy.

LOM-test configuration 
For the KM3NeT13 cruise a test-string has been developed with various monitoring sensors. Instead of optical modules, each glass sphere will hold a concrete dummy weight. Two sensors will measure tilt and compass at a rate of 10 Hz. Inside the data cable, pressure variations will be monitored. The anchor will hold a video system and a few glass spheres are equipped with cameras.
In order to accomplish multiple test-deployments in as many days, two complete LOMs have been manufactured. The first LOM will be deployed and recovered at sea from the Pelagia, while the second LOM is being remounted with the string in Motril. Every night the Pelagia enters Motril-harbour to exchange equipment plus empty LOM-I and loaded LOM-II, and vice versa.