OPERATION - Glider deployment
The SeaExplorer is an underwater glider which moves vertically through the column of water to collect different types of data.
It is a semi-autonomous machine capable of moving horizontally and maintain a specific heading to explore the shoal by itself. A standard navigation cycle is called a “yo”. When the glider is working at sea, the standard navigation cycle starts when it is at the surface, receiving time and position through GPS while communicating through satellite connexion (Iridium) with its pilot, who is operating from Meyreuil (ASLEAMAR, south of France).
It can also communicate data from its internal sensors (e.g. diving profile, temperature, pressure). On his side, the pilot responsibility is in charge to check the status of the device and can modify the glider’s trajectory.
The propulsion system is uncommon, as the SeaExplorer is not propelled by an engine but instead it uses the principle of buoyancy. The SeaExplorer can change its density via an external oil bladder (liquid with a lower density than sea water) which deflates or inflates, whether it needs to go up or down. Once the ballast system is ready, the glider heads at a downward angle and dives. It will then use the diving speed to orientate itself and aim for its first waypoint.
This energy efficient way of travelling allows the glider to stay at sea for a very long period of time. It is equipped with a hydrophone (device used to record underwater sounds like sea mammals’ vocalisations) and a CTD sensor to sample salinity, temperature and depth in a continuous way. During its mission the glider will regularly perform 700 meter dives.
The glider was put in the water on the 1st of May with the help of a semi-pneumatic zodiac. During a period of twelve consecutives days, it will continuously record data, independently from the operations aboard the Marion Dufresne. This operation was coordinated by Adrien and the pelagic team, while in satellite connexion with the land-based pilot. The recovery is planned to take place just before the departure from the Walters shoal at the end of the mission.
Acoustic Data acquired through this sophisticated device will allow scientist to detect and identify different sea mammal species that could be present in the area (e.g. Antarctica blue whales, pigmy blue whales, humpback whales, fin whales, dolphins and sperm whales). The acoustic propagation is faster and goes further in seawater than in air. Hence, the detection of those species can be done at a higher distance than visual observations.
The CTD data will be used to calculate sound velocity profiles in seawater, depending on sampling depth.
The received sound and mammal detection will be put in relation with the potential observations done by the megafauna observers team, Hélène and Anjara.
Project supported by TOTAL FOUNDATION:
