The Ocean Floor Observation System (OFOS), used during Polarstern research cruise PS101 to the Langseth Ridge in the Central Arctic, was a towed underwater camera system equipped with both a high-resolution photo-camera (iSiTEC, CANON EOS 5D Mark III) and a high-definition video-camera (iSiTEC, Sony FCB-H11). The cameras were mounted on a steel frame (150L x 92W x 105H cm), together with two strobe lights (iSiTEC UW-Blitz 250, TTL driven), three parallel 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 with a 85 cm tail to additionally mount an EdgeTech 2205 bathymetric side scan and BlueView M900-130 forward looking sonar systems, to become the Ocean Floor Observation and Bathymetry System (OFOBS). Auxiliary sensors include an iXBlue PHINS 6000, an AML Micro-X 6000 P-Xchange pressure sensor and an AML Micro-X 6000 SV-Xchange sound velocity probe.The side scan sonar operates on two frequencies (230 kHz & 540 kHz) and the bathymetric array receives the high frequency. During PS101 the OFOBS has been flying on an average altitude of 3m above the seabed. The resulting achievable sonar ranges were 100m (low frequency) and 50m (high frequency) to both sides of the vehicle. Bathymetry in *_binned files is binned with 800 equidistant data points of 10cm distance, 40m to both sides. Additional _stave files contain the raw stave data. Stave files can be replayed with EdgeTech Discover Bathymetric to bin the bathymetry with different settings.

Some post processing software does not recognize the recorded vehicle depth. For additional depth correction, the INS log is attached.Offset from Sonar to Navigation Reference# x: Forward# y: Starboard# z: Vertical positive upx,y,z = 0.507,-0.006,0.212