Mohamad-Ziad Charif - Antares

Figure 3.22: Distribution of sea current speed (on the left) and its horizontal direction(right).The Onshore calibration of the OMs offset (Figure3.24 ) is done in a darkroom to eliminate unwanted light sources. A controlled laser beam is sent to theOM as seen in figure 3.23 . The offset is calculated in reference to the first OM ofthe first floor.The in situ calibrationon the sea bed.is actually a set of three different calibrations done• Using the LED beacons[93] the OM offset can be recalculated (Figure 3.24) using these beacons that flashes light at λ = 470 nm. These beacons existon floors 2, 9 , 15, and 21 of each line. This is done by flashing the LEDbeacons and measuring the time differences of the signal among the differentOMs and a reference OM. However, since the first LED beacon is on thesecond floor of each line, the offset can not be measured for the first flooras the light from the LED is emitted upwards, this is solved using the laserbeacons.• Using the laser beacon[93] on the BSS of lines 8. This laser beacon whichflashes laser beams at λ = 532 nm can calculate the inter-line offset betweenall lines and line 8. This is done as well by flashing the laser beacon andmeasuring the time differences of the signal among the different lines. Inaddition, the laser beacon can measure the OM offset for the first floors ofeach line as as the laser beacon is placed below the first floor.• 40 K which occurs naturally in sea water, it is a radioactive isotope of Potassium.The decay of 40 K can produce photons which can help in an indepen-54