ICE THICKNESS MEASUREMENT METHOD

THE PROPOSED CONCEPT FOR MEASURING ICE THICKNESS FROM A SUBMARINE IS FUNCTIONALLY SIMILAR TO THE BQS-15 IN THAT IT MEASURES THE HYDROSTATIC PRESSURE AT THE SUBMARINE AND THE UPWARD DISTANCE TO THE UNDERSURFACE OF THE ICE. THE PRESSURE IS DUE TO THE WEIGHT OF THE WATER COLUMN PLUS THAT OF THE ICE; SO, FROM THE TWO MEASUREMENTS, THE WEIGHT AND HENCE THE ICE THICKNESS CAN BE COMPUTED. HOWEVER, RATHER THAN USING AN UPWARD PING TO FIND THE DISTANCE TO THE ICE, WE PROPOSE TO USE THE RADIATED NOISE OF THE SUBMARINE BY CORRELATING THE REFLECTED NOISE WITH THE TRANSMITTED NOISE. PRELIMINARY CALCULATIONS INDICATE THAT IN THE ABSENCE OF LOUD ICE CRACKING NOISES OR PRESSURE RIDGES THIS RADIATED NOISE IS SUFFICIENTLY LOUD FOR THE PURPOSE. THE PROPOSED PHASE I EFFORT INVOLVES ACOUSTIC MODELING AND SIGNAL PROCESSING ANALYSIS. THE PRINCIPAL QUESTIONS TO BE ADDRESSED ARE THE EFFECT ON SYSTEM PERFORMANCE OF THE SPATIAL DISTRIBUTION OF NOISE SOURCES ON THE SUBMARINE, AMBIGUITIES GENERATED BY LINE COMPONENTS, THE PREVALENCE AND OPERATIONAL IMPORTANCE OF ICE CRACKING NOISES AND PRESSURE RIDGES, AND THE GENERAL CHARACTERISTICS OF THE ACOUSTIC REFLECTION COEFFICIENT OF THE ICE. WE WILL ALSO CONFIRM THAT THE SUBMARINE RADIATED NOISE IS SUFFICIENTLY LOUD.