Accordingly, the stage was set to deploy the underwater robot on the evening of 11 July 2016 for its long mission at the AWI deep-sea observatory 'Hausgarten' at a water depth of 2,500 metres. A video-guided deployment system (the so-called launcher) brought the crawler safely to the seabed, where it is now to perform its measurements every week. It first moves 15 metres in order to reach an undisturbed area. An image recognition camera checks the surface there: If any stones or the like are recognised, Tramper travels on for another two metres. Then, a high-resolution photo of the measurement site is taken before the measurement begins. During this process, sensors are placed in the sediment in small increments of 0.1 millimetres, in order to measure the oxygen distribution in the seabed.
"After the measurement, Tramper goes to sleep for a week, to save energy. Ultimately, it should perform more than 52 such measurement cycles – and at a temperature of minus 1.8 degrees Celsius, which places a strong demand on the batteries," says Dr Frank Wenzhöfer, biologist at the Helmholtz Max Planck Joint Research Group for Deep-Sea Ecology and Technology. The scientists want to use the Tramper measurements in order to investigate the activity of microorganisms on the seabed.
Microorganisms are particularly responsible for the degradation of organic material in the deep seabed. Bacteria convert the remains of dead algae and animals while consuming the oxygen in the seabed. Depending on how much dead algae arrive on the seabed, there will be more or less bacterial activity and, therefore, more or less oxygen consumption. "We want to use the measurements provided by Tramper to identify the natural variation over the course of the year," says Dr Frank Wenzhöfer in explaining the scientific objectives of the mission. "Statements can also be made about how the ecosystem of the Arctic seabed responds to environmental changes. Such data about the Arctic are still incomplete," the microbiologist adds.
"For studies by deep-sea ecologists, we have developed a new multi-sensor revolver-system, which is intended to guarantee the consistent quality of the measurements," says AWI engineer Dr Johannes Lemburg about the development work that is occurring in the context of the Helmholtz Alliance ROBEX (Robotic Exploration of Extreme Environments). "It makes it possible to measure with three sensors at the same time and to exchange them after a certain number of measurements. Such an exchange of sensors can be performed six times with each of the three revolver, allowing a total of 18 sensors to be used," says Johannes Lemburg of the sophisticated system.
Engineers and scientists are already looking forward to their next expedition in the coming year: "In the summer of 2017, we are going to return with the RV Polarstern to the AWI 'Hausgarten', and we hope to pick up the Tramper safe and sound and full of valuable data!"