Seabed photographs taken along OFOS profiles during POLARSTERN cruise PS101 (ARK-XXX/3)

The cameras were mounted on a steel frame (140L x 92W x 135H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three laser pointers spaced with a distance of 50 cm used to estimate the size of seafloor structures, four LED lights, and a USBL positioning system (Posidonia) to track the position of the OFOS during deployments.

For PS101 the OFOS was upgraded to additionally mount sidescan and forward looking sonar systems. In automatic mode, a seabed photo, depicting an area of approximately 4 m**2, with variations depending on the actual height above ground, was taken every 20 seconds to obtain series of "TIMER" stills distributed at regular distances along the profiles that vary in length depending on duration of the cast. At a ship speed of 0.5 kn, the average distance between seabed images was approximately 5 m.