Measurements of light transmission in deep sea with the AC9 trasmissometer

The NEMO Collaboration aims to construct an underwater Cherenkov detector in the Mediterranean Sea, able to act as a neutrino telescope. One of the main tasks of this project, which implies difficult technological challenges, is the selection of an adequate marine site. In this framework the knowledge of light transmission properties in deep seawater is extremely important. The collaboration has measured optical properties in several marine sites near the Italian coasts, at depths > 3000 m, using a setup based on a AC9, a commercial trasmissometer, manufactured by WETLabs. The results obtained for the two sites reported in this paper (Alicudi and Ustica), show that deep seawater optical properties are comparable to those of the clearest waters. (C) 2002 Elsevier Science B.V. All rights reserved.