Preface The expedition ARK XIX/3 with the German icebreaking RV ...

indicated an insulation problem with the "Victor 6000" so after recovery the engineers
started to work immediately to identify the source of this problem. It was decided to
change the tether cable which was the suspected cause of the problem. The spare cable
was installed during the late afternoon; however, the following system check indicated
that there was no communication between the ROV and the depressor. Since the tether
cable has several fibre optic cables inside, the engineers switched the communication
data link from one to the other. This time consuming procedure lasted until midnight.
While repairing the "Victor 6000" system several CTD casts were carried out at stations
along various mounds in the vicinity. Some complementary 38 kHz echo sounder profiles
were also on our station list before the next dive of the ROV.
Another operation of the ROV took place at the so called "Giant Mound Cluster", a group
of several mounds close together on the Porcupine Bank followed by a survey course
over the "Scarp mounds" at about 800 m water depth. This microbathymetry survey at
altitudes above seafloor of about 10 metres was from time to time interrupted by video
surveying the seafloor at closer distance. The weather conditions were favourable to
continue this dive from Sunday until Tuesday evening. Dive operations of about three
days are possible without any problems with such a work-class ROV. This is one of the
main advantages in using ROVs instead of manned submersibles in deep-sea research
because manned vehicles are much more time limited in their operation.
Shortly after the end of the "Scarp mound" mission the wind increased considerably as
predicted by the meteorologist onboard. Wind speed around 8 Beaufort would have
caused severe problems during the recovery operation. Until 5 o'clock in the morning
such wind speeds were measured – by far too high for save deployment and operation of
a ROV. In order to complete our data set we decided therefore to operate other gears,
used the ship borne multibeam and sediment profiling sonar system together with the
ship borne fishery echosounder. At 4 pm – the wind speed did already decrease during
the morning but the sea state needed some hours more to calm down – "Victor 6000" was
deployed for the last dive at the "Hedge mounds" during this cruise leg. On Thursday the
wind increased suddenly as the swell did. The recovery of "Victor 6000" from its last dive
became rather difficult. Because of the experience of the 1 st officer and his crew on deck,
the well trained ROV pilots and the officers on the bridge we got the ROV safely out of the
water.
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