Acoustic Data Telemetry from Beneath the Ocean Floor

The UK Department of the Environment, as a part of an international research program, has sought to determine the viability of high-level nuclear waste disposal by "penetrator projectile" embedment many tens of metres beneath the ocean floor. Experiments using "model" penetrators, instrumented with constant frequency acoustic sources to allow Doppler shift measurement of penetrator velocity, and hence calculation of penetration depth, have now been routinely conducted for some years. A brief description of the Doppler method, together with recent design improvements and field observations of performance, is presented. A generic development of the Doppler equipment is then described. This new system, in addition to providing Doppler measurement allows, after embedment, measurement of down-hole pressure and sediment strength to be telemetered through tens of metres of ocean sediment and several thousand metres of ocean water, results from sea trials in the Mediterranean Sea and Atlantic Ocean are presented.