Slide show


Ocean measurements sometimes involve a subsurface mooring, consisting of an anchor, a mooring line, instruments distributed along the mooring line, and floatation to hold the mooring erect, all submerged a considerable distance below the surface. A mechanical release device controlled by a timer or remote-control acoustic commands releases the anchor to allow the float to ascend to the surface for retrieval of the equipment.

Occasionally some part of the mooring fails, or deepwater fishing damages the instrument mooring. If the mooring comes to the surface when no one is around to pick it up, the equipment and measurement data are lost.


We developed a loose-mooring alarm that announces itself to a satellite telemetry system when it floats at the ocean surface. This is an electronics package that is installed in a deepwater floatation sphere, with batteries, an orientation sensor, a satellite radio transmitter, an antenna, and a microprocessor contoller that is used to manage power, sensing, and satellite transmissions.

When the "witness buoy" is installed in the underwater mooring tackle, its normal orientation is sensed to keep the alarm system in its "sleep" mode. If the mooring comes loose and floats to the surface, the change in orientation of the device is sensed, and the satellite data transmissions are enabled. The satellite system forwards data that identifies the mooring and its approximate geographic position to the researcher over the Internet. Transmissions from the buoy can be used to locate the drifting equipment.


This system has enabled recovery of several oceanographic instrument moorings that escaped their anchors due to fishing activity or other causes.