To obtain coordinates of each OM during data taken period a custom Long-Base-Line (LBL) Underwater Acoustic Positioning System (L-UAPS) was deployed at the detector. The system consists of a bottom LBL-antenna, comprised of nodes moored at the bottom of the telescope strings, and acoustic beacons, attached to the strings (three per string).

The measurement cycles are launched by an operator at the shore center (the minimum duration of a measurement cycle is limited to 30 s). The L-UAPS’s positioning accuracy of 5 mm was experimentally proven for beacons 160 m away from the bottom antenna, thus allowing to track even the smallest movements of the drifting beacons. Measurements performed since the Cluster-2012 starts to operate.
Figure 1 shows a distance monitoring between the bottom and top beacons of the string in April 2012.