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ROV-Based Revolver Marker Dropper For Consistent Seafloor Surveying

By Sascha Lehmenhecker
Computer Science Engineer
and
Thorben Wulff
Mechanical Engineer, Ph.D. student
Alfred Wegener Institute for Polar and Marine Research
Bremerhaven, Germany



As part of an Arctic expedition of the RV Polarstern in July and August 2011 to Fram Strait, a deep-sea revolver marker dropper (RMD), developed by the Alfred Wegener Institute for Polar and Marine Research (AWI), was deployed around 2,500 meters depth on the ROV Kiel 6000 to mark a 350-meter transect for repeated seafloor visual observations.

Temporal variations in spatial patterns of benthic epi- and megafauna organisms have been monitored since 1997 at HAUSGARTEN, AWIís deep-sea observatory for detecting and tracking the impact of large-scale environmental changes in the transition zone between the northern North Atlantic and the central Arctic Ocean. High-resolution pictures of the seafloor and its inhabitants were taken almost annually at approximately 7.5-meter intervals using a towed photo and video ocean floor observation system.

However, as a towed system could never cover the exact same deep-sea line, the institute decided to conduct comparable visual observations over time with an ROV-based vertical camera system along a defined, shorter transect.

The RMD was developed to mark this transect, deploying a multitude of tags at about 10-meter intervals, which allows the ROV pilot to follow the transect from one marker to the next.

This tool will ensure capturing exactly the same area over time in seafloor surveys.

Design Goals
The ROV Kiel 6000, owned by the GEOMAR | Helmholtz Centre for Ocean Research, has several interfaces and a large payload capacity for underwater applications, so the development and integration of the RMD into the ROV was relatively simple. The RMD was designed to be as compact and lightweight as possible for easy handling. The goal was to develop and construct within three months a tool able to drop a large number of permanent markers that would be highly visible by the ROVís cameras. The RMD had to be designed to work in extreme pressures and temperatures, such as full ocean depth and -1° C. The use of cold-resistant components was therefore as mandatory as the planning for tolerances and free spaces to allow for thermal expansion. To continue this article please click here.


Sascha Lehmenhecker is a member of the deep-sea research group at the Alfred Wegener Institute for Polar and Marine Research. He is a computer science engineer with electronics training and specializes in microcontroller applications and circuit design. He received a bachelorís degree from the University of Applied Sciences in Bremerhaven, Germany.

Thorben Wulff is a Ph.D. student at the Alfred Wegener Institute for Polar and Marine Research. He holds a bachelorís and masterís in mechanical engineering from the University of Applied Sciences in Mannheim, Germany. Funded by the EU as part of the Eurofleets project, he is currently working on interoperable payloads for European AUVs.




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