Techniques for Ocean Bottom Measurements of Magnetic Fields with a Superconducting Magnetometer

A superconducting quantum interference device (SQUID) magnetometer cooled by liquid helium was placed on the ocean floor at a depth of 100 m in order to receive extremely low frequency radio transmissions. A nonmagnetic concrete and fiberglass platform anchored a fiberglass pressure vessel containing the magnetometer firmly to the ocean bottom. The helium gas evolved from the boiling liquid helium was vented through a hose to the surface. Details of the apparatus and the techniques used to install and recover the SQUID magnetometer are given.