Long-term moorings

It is a long-term data acquisition system that records in-situ pore pressure and temperature gradients, among other things. It was developed at MARUM for use at depths of up to 4 and 6 kilometres. The steel girder system consists of a 5.5 metre long lance, a base plate and a tower, which serves as a housing for the data acquisition electronics. The access for the pore water, which is channelled to the pressure sensor via a thin pressure pipe, is located at the tip of the lance. The temperature gradient is recorded via a 6 metre long thermistor string attached to the outside of the lance. The absolute water pressure and the temperature of the soil water are also measured.

NCB CAD — Diagram des Komplettsystems mit Sensorien und Auftriebskörpern

The system is deployed in free fall. To do this, the device is brought to 100m before bottom contact and then detached from the ship's wire using an acoustic releaser. To ensure a stable decent, there are 4 glass floatation spheres behind the lance. The sphere closest to the lance also serves as the housing for the differential pressure transducer.