Lined up along the wet and slippery deck of the landing craft Castor 02 are four great spheres, each about 2.5 meters (8 feet) across. Wrapped in silver-colored material, they resemble the EVA pods in Stanley Kubrick's science fiction movie 2001: A Space Odyssey. But these Launchers of Optical Modules (LOMs) will not take off into deep space. Instead, they are bound for the bottom of the Mediterranean Sea, some 2,450 meters below the ship. Paschal Coyle, director of research at the Center for Particle Physics of Marseille, peels away part of the protective wrapping on one of the giant spheres, to reveal some of the 18 shiny Digital Optical Modules (DOMs) that are hidden inside. As large as a typical beach ball, each spherical DOM is outfitted with 31 photomultiplier tubes, devices sensitive enough to detect individual photons. At 9-meter intervals, the DOMs are attached to 200-meter-long cables that will vertically unroll from an anchor on the seafloor once deployed. Marie-No?lle Fabre, a support engineer for the company that provides sonar navigation equipment, stresses the impressive precision of the underwater operation. "At a depth of almost 2.5 kilometers, we succeed in positioning the detector lines with an accuracy of just two meters," she says.
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