Site description

The bottom mooring consists of a camera, lights, temperature sensors, batteries, acoustic modem, and a master controller. An aluminum pressure case with an acrylic lens houses a Sony PAL video camera and a PC-104 computer with a video frame grabber. On command from the master controller, one of two 150-watt lights are turned on and the camera generates an image that is then broken into 64 tiles. Each tile is compressed by a factor of 35:1 using wavelet theory to yield a complete image of approximately 16K using an 8 bit gray scale. Temperature is measured at two places in view of the camera and at one place on the camera frame with titanium housed PRTs cabled to the master controller. Data are transmitted from the bottom package at 300 baud with an acoustic modem operating in the 8-13 kHz range. The bottom system is powered for a one-year deployment with 564 alkaline D cells. The system was deployed by free-falling the bottom package and was moved into position with the ROV ROPOS. A green laser was mounted on the system to aid in pointing the camera.

A 2.5m disk buoy is anchored very close to the camera and moored taut with 3/4 and 7/8 inch nylon line to keep a tight watch circle. A transducer for the acoustic modem is mounted in the bridle of the buoy and electronics and batteries are located in an instrument well. A microcontroller in the buoy receives data from the acoustic modem and further compresses and formats the data for transmission. A 40-watt transmitter and an omni-directional antenna are used for the GOES data telemetry. A buffer representing one tile (250 bytes) is sent every hour, except one transmission per day has 24 hourly values from the 3 temperature probes. Consequently, a new picture is available every 4 days and temperature plots are updated daily.