The Charles Stark Draper Laboratory, Inc.

Massachusetts Institute of Technology

John M Dahlen

John T Shillingford, Jr

John F McKenna, Jr

William E Toth

Philip N Bowditch

Frank J Siraco

James R Scholten

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

A system for measuring ocean characteristics. The system includes a sensor assembly and an associated means to control the system buoyancy to achieve cyclic ascent and descent at controlled speeds, either along a mooring line or free-drifting. Buoyancy control is provided by a pump assembly including two rolling diaphragm-sealed, low friction displacement pistons driven by a high torque d.c. motor operated at low speed. There are four functional groups of data gathering instrumentation. The first group measures horizontal water transport, and includes sensors for current (flow velocity), system azimuth, system tilt, and vertical velocity. The second group provides a determination of salinity, and includes sensors for conductivity, temperature and pressure. The third group monitors conditions within the system, and includes sensors for internal temperature and humidity. The fourth group monitors conditions utilized in the buoyancy control, and includes sensors for pressure (depth and depth rate) and piston position. A programmed microprocessor configuration provides overall operational control for the system.

Adaptive controller for ocean characteristic measurement system

Buoyancy control for ocean characteristic measurement system

A system for measurement of ocean current near the surface wave field. The system includes a controlled buoyancy platform having a current sensor. Upper and lower plural roller assemblies are affixed to the platform for limiting platform motion along a guide line. In one form, each guide assembly includes a plurality of rollers adapted to freely track the guide line so that the platform is both substantially free to move along the guide line in response to pressure gradients from the surface wave field and also substantially decoupled from twisting and axial motions of the guide line.

System for measuring ocean current

A recording instrument for use in ocean depths and like remote locations and adapted to provide meaningful readings of temperatures and pressure, for example, at such locations over a long period of time without attendance. Analog signals from transducers, which indicate the level of the thing-to-be-measured, are processed to give an averaged digital signal that is then stored on a magnetic tape. The system is battery powered. The instrument detailed is for use at ocean depths where the instrument housing and attachment to a mooring line are of particular importance.

Growing community of inventors

Duxbury, MA, United States of America

John M Dahlen