In operation, an AUV like MARUM SEAL couldn't be actively positioned like an ROV - in contrast, a sequential waypoint navigation is active on an AUV, once it is in mission mode. Nevertheless, decoupled from his own vehicle-based waypoint navigation the AUV could be tracked from an independent ship-bourne system, continuously asking for the actual position of the diving AUV. In our case, two different ultra-short-baseline-tracking systems (USBL) will be operated on cruises; IXBLUE POSIDONIA (usually hull-mounted on the research vessels) for waterdepth up to 6000 m and the IXBLUE GAPS system (mobile) up to 3000 m waterdepth. Common for both systems, they need to operate a compact acoustic antenna on board the research vessel, connected to an inertial-navigation system and GPS signal, in order to calculate the valid ships-position. Each 5 second, an acoustic transmit-pulse will be sent to the diving AUV. Onboard the AUV, a separate acoustic transponder will send a reply pulse to the antenna. Based on travel-time delays between send/receive signal, the USBL system could calculate the exact position of the diving AUV (+/- 5 m, typically). In general, the USBL tracking method is not as precise as long-baseline tracking (LBL), but no seafloor transponder needed to be placed and the AUV/support ship are not bounded to a given geographic position.
Adapter-pole to attach the GAPS antenna and the AUV acoustic command modem to a moon-pool adapter-device (RV POSEIDON).
Installation of equipped moon-pool device onboard RV POSEIDON (GAPS antenna, left; acoustic modem, right).
GAPS antenna pole of RV PELAGIA.