R&D for an innovative acoustic positioning system for the KM3NeT neutrino telescope F. Ameli a , M. Ardid b , V. Bertin c , M. Bonori a , M. Bou-Cabo b , C. Calı d , A. D’Amico d , G. Giovanetti a , M. Imbesi d , P. Keller c , G. Larosa b , C.D.Llorens b , R. Masullo a , N. Randazzo e , G. Riccobene d,n , F. Speziale d , S. Viola d a Universit a La Sapienza and INFN Roma 1, Piazzale A.Moro 2 I-00185,Rome,Italy b Institut de Gesti o Integrada de Zones Costaneres-UPV, Cra.Nazaret-Oliva S/N E-46730 Gandia, Valencia,Spain c CPPM,CNRS/IN2P3 et Universite ´ de la Mediterrane ´ e,163,Avenue de Luminy, Case 902, 13288 Marseille Cedex 9, France d LNS-INFN,Via S.Sofia 62 I-95123, Catania,Italy e Universit a di Catania and INFN Catania, Via S.Sofia 64 I-95123, Catania,Italy For the KM3NeT consortium a r t i c l e i n f o Available online 5 May 2010 Keywords: Underwater neutrino telescope KM3NeT Calibration Acoustic positioning system Transceiver a b s t r a c t An innovative Acoustic Positioning System for the km 3 -scale neutrino telescope has been designed and is under realization within the KM3NeT Consortium.Compared to the Acoustic Positioning Systems used for the km 3 demonstrators, ANTARES and NEMO Phase 1, this new system is based on the ‘‘all data to shore’’concept and it will permit the enhancement of detector positioning performances, reduction of costs and its use as real-time monitor of environmental acoustic noise. & 2010 Elsevier B.V. All rights reserved. 1. Introduction The Acoustic Positioning System (APS) is a sub-system of the km 3 -scale neutrino detector that must provide mandatory information during the deployment and the operation phases of the telescope [1].During the deployment phase,the APS must provide the position of telescope’s mechanical structures,in a geo-referenced coordinate system, with an accuracy of about 1 m. This is important both for a safe deployment of the mechanical structures and for the determination of the absolute position and pointing direction of the telescope (necessary for the localization of astrophysicalsources).During the telescope operation phase, the APS data are used to recover the positions of optical modules (OMs) in deep sea.In fact,in order to effectively reconstruct the muon tracks via the optical Cherenkov technique, the OM coordinates must be known (in a geo- referenced system) with an accuracy of about 10 cm, i.e. qualitatively speaking, about the length of the OM diameter. Moreover, in deep sea, the mechanical structures holding the optical modules move under the effect of currents and, therefore, their positions must be continuously monitored (e.g.about twice per minute under conditions of low sea currents, as measured in deep-sea sites candidates for KM3NeT [1]). A deep-sea APS is composed by three main items: (1) a so called Long Base-Line (LBL) of acoustic transceivers, anchored on the seabed in known positions; (2) an array of acoustic receivers (hydrophones)rigidly connected to the telescope mechanical structures; (3) a PC farm for the APS data analysis, on shore.The hydrophones’positions are recovered by measuring the Acoustic Transit Time (ATT) of the LBL transceivers signals on the hydrophones,thus determining via triangulation, the position of the hydrophones with respect to the geo-referenced LBL.This innovative APS has been designed to accomplish full integration with the electronics and mechanical design proposed by for the KM3NeT telescope [1].In particular,this new APS upgrades the systems developed for NEMO Phase 1 [2] and ANTARES [3].It provides a better accuracy in the TOA measurement (thus a better position accuracy), thanks to absolute time synchronization between transceivers and hydrophones. It is also scalable to a km 3 detector and allthe components have been tested for long term installation at 3500 m depth. Eventually, it uses commercial audio electronics components and technology, so that costs of the electronics and data acquisition chain have been strongly reduced. 2. Proposal for the KM3NeT APS The general scheme of the proposed APS is sketched in Fig. 1. Two hydrophones are installed on each storey of the detector. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A 0168-9002/$ - see front matter & 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.nima.2010.04.130 n Corresponding author. E-mail address: riccobene@lns.infn.it (G. Riccobene). Nuclear Instruments and Methods in Physics Research A 626-627 (2011) S211–S213