The Charles Stark Draper Laboratory, Inc.

James R Scholten

John M Dahlen

John T Shillingford, Jr

Richard K Araujo

Robert W Reid

Matti Soikkeli

Narender K Chhabra

A low-cost floating drifter adapted to accurately follow near-surface ocean currents and transmit periodically to monitoring satellites data and position-determining information. Global tracking of ocean currents is made economically and scientifically feasible by the use of large numbers of such drifters. The drifter includes a floating surface buoy in the approximate shape of an oblate spheroid and containing an electronic system, a slotted plane antenna, transmitter, sunrise and sunset detector, environmental sensors, buoy hull strain sensor and battery power supply. The surface buoy is stabilized and induced to follow ocean currents by a drogue suspended from the bottom center surface. The drogue includes a wire-cored buoyant rope of up to hundreds of meters in length and weighted to a slight negative buoyancy. The drogue may also include an elongated cylindrical sock of substantially greater diameter than the rope. By means of the sunrise and sunset detector and the electronic system, the transmitter is controlled to operate only during selected passes of a solar synchronous satellite so as to conserve the battery and permit unattended life of up to several years. By means of the hull strain sensor and the electronic system the transmitted signal contains data from which the drogue integrity can be determined. Other status and environmental data are also transmitted. The drifter has special provisions to resist corrosion, fish-bite damage and biological fouling.

Low cost drifter

The present invention is a magnetic field measuring system and method for generating a magnetic field signal representative of the Earth's undistorted magnetic field at any given spatial location over a measurement period. The measured undistorted magnetic field is substantially independent of distortions due to any magnetically susceptible material within the measuring system and is substantially independent of internal magnetic fields generated by magnetic field sources within the system.

Method and apparatus for measuring the undistorted magnetic field of the

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Sudbury, MA, United States of America

James R Scholten