The first generation of underwater camera sled or Towed Optical Assessment Device (TOAD) used for the collection of optical validation data was a MiniBAT 8820 manufactured by Guideline Instruments. The MiniBAT is a tow body designed to be towed at 3–10 knots while remotely guided by an operator on the towing vessel, who adjusts wing angle on the sled to keep it close to the seafloor. This iteration of TOAD was configured with a single Sony DCR-PC110 Digital Video Camera in a modified Gates underwater housing. It also featured a Canon Power Shot G1 Still Camera (modified by CRED engineers) in an Ikelite housing rated to 60 m, and slaved to an Ikelite DS-50 strobe. Illumination was provided by two 500 W DeepSea Power & Light model 710-0400601 underwater lights. The Canon camera had a custom-built timer that enabled the user to select a constant time interval (ranging from approximately 5 seconds to 2 minutes) between photographs. An interval of 30 seconds was typically selected, which, assuming a mean velocity for the camera sled of 1.5 knots, resulted in one photograph approximately every 20 m.
The TOAD was damaged during a cruise in February 2002 when it failed to respond to wing adjustments to make it climb rapidly to avoid a suddenly encountered rise on the seafloor. Subsequent tows were conducted as drift deployments. At each station the ship was positioned with the wind on the starboard side and drifted downwind; occasional light turns were applied to the ship's screws if necessary to reduce the ship's motion. The operator continued to monitor the vehicle and provided commands to raise or lower it to keep the camera just above the bottom. This sled was lost off Baker Island during a cruise in 2004, when it caught on a ledge and the cable parted.
A similar version of that TOAD was assembled together from parts and successfully deployed for the remainder of that cruise and several subsequent ones. A MiniBAT frame was extensively modified from its original configuration and was configured with a single ROS model 54-00100-13 color underwater video camera and two 500 W DeepSea Power & Light model 710-0400601 underwater lights mounted on the original sled frame. The MiniBAT pressure sensor and wing controller was also mounted on the frame but no wings were installed. Communication between the sled and the surface was enabled via an underwater electrical cable (cable 1, blue in color) with a separate load-bearing line to support the sled frame. The electrical cable was clipped to the line at regular intervals upon deployment and removed upon recovery.
An opportunity arose with a contract from an outside agency to collect significant additional optical data at the Garapan Anchorage outside of Saipan harbor in 2004. Completion of that project required camera sleds that could be deployed from small boats, which were designed and built by Deep Ocean Engineering. Named the Towed Aquatic Resource Assessment System or TARAS, the two new sleds were built on modified Phantom ROV frame. They are equipped with a Deep Sea Power & Light Multi SeaCam 2060 low-light color video camera, two 500 watt DeepSea Power & Light model 710-0400601 underwater lights, a Tritech PA200/20-PS sonar altimeter to detect the height of the camera above the seafloor, a Deep Sea Power & Light SeaLaser 100 pair of parallel lasers for scaling, a compass to determine the sled heading and orientation, and a depth (pressure) sensor. The camera sleds are attached to a control console (right-hand figure above) via 200 m of 0.5 inch diameter umbilical cable. A video display monitor mounted on the control console is used to monitor the position of the sled relative to the seafloor. Video data are recorded to digital video cassette using a video recorder mounted on the control console. Hypack Max (version 2.12A) hydrographic survey software is used to record GPS data, water depth, length of umbilical cable in the water, and camera sled information (height, heading, etc.), which provide ship and camera sled positions for the duration of individual tows.
When operated from the NOAA Shi Hi‘ialakai, the TOAD is equipped with a model 4330B transponder allowing its position to be track with the vessel’s model 4410D-01 Trackpoint II Ultrashort Baseline Navigation system, with a 4211A hydrophone and a 4740A VRU/amplifier. The system currently enables the TOAD’s position to be resolved with a total horizontal uncertainty of approximately ± 25 m, although we anticipate better results as we learn more about how to setup and operate the system.
The sleds are currently being reconfigured to simultaneously run both a downward looking video camera for collecting vertical imagery of the benthos, and a second and obliquely-angled video for obstacle avoidance and assessing fish and macroinvertebrate communities. The modifications will include a several-fold enhancement in illumination, provided by the addition of a DeepSea Power and Light SeaArc2 HMI light. A 350 m custom umbilical cable featuring 3 coax and 12 other conductors and a custom electric winch with slip rings and a remote controller are also being fabricated to enhance the safety and efficiency of optical data collection.
Identification of particular vendor’s equipment does not imply endorsement by SOEST or NOAA.