Seismo-acoustic detection, identification, and tracking of stealth aircraft

• US 4,811,308 A
• Filed: 10/29/1986
• Issued: 03/07/1989
• Est. Priority Date: 10/29/1986
• Status: Expired due to Fees

• Current Assignee: The United States of America As Represented By The Secretary of Agriculture
• Original Assignee: The United States of America As Represented By The Secretary of Agriculture
• Inventors: Michel, Howard E.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Pihulic, Daniel T.
• Application Number:
  US06/924,707
• Time in Patent Office: 860 Days
• Field of Search: 367/135, 367/136, 367/124, 367/129, 367/118, 367/93, 340/565, 340/566, 340/541, 340/522, 102/211, 102/427, 102/419, 181/122
• US Class Current: 367/136
• CPC Class Codes: G01S 3/802 Systems for determining direction or deviation from predetermined direction
• CPC Class Codes: G01V 1/001 Acoustic presence detection
• CPC Class Codes: Y10S 367/906 Airborne shock-wave detection

Abstract

An aircraft detection system which detects and tracks aircraft using: arrays of seismic and acoustic sensors, a set of junction circuits, a set of subarray circuits, several slave computers, and a master computer. Each junction circuit relays detected signals from several adjacent sensors to a subarray circuit and command signals to each of the sensors to adjust the gain of their output signals. Each subarray circuit receives and unites the outputs of several adjacent junction circuits into a subarray which has a particular geographical location in the array of sensors. Each slave computer forwards detected signals from single subarray circuit to the master computer, and relays command signals back to each individual sensor. Each subarray is able to track the seismic or acoustic signature of an aircraft as it travels across the regular distribution of sensors. Each subarray is thereby able to define an azimuth to the target aircraft. Collectively the information from several subarrays yields several azimuths from which the position of the aircraft may be located by triangulation of the azimuths.

Claims

1. A detection system for detecting aircraft comprising:

an array of sensors which senses seismic and acoustic signals generated by said aircraft, said array outputting therefrom detection signals, wherein said array includes a plurality of subarrays of seismic and acoustic sensors which are in a regular distribution over a geographic area of terrain;

a plurality of junction circuits, each of which is electrically connected to sensors which are adjacent to each other in said regular distribution, said junction circuits receiving and amplifying said detection signals to output amplified detection signals;

a plurality of subarray circuits, each of which is electrically connected to some of the junction circuits whose sensors are adjacent to each other in said regular distribution and collecting and relaying said amplified detection signals produced by said junction circuits, said subarray circuits thereby uniting adjacent sensors into a distinct subarray associated with a particular geographic location within said geographic area;

a plurality of slave computers, each of which receives and forwards said amplified detection signals from one of the plurality of subarray circuits, and each relaying command signals back through the subarray circuits and junction boxes to its sensors in its distinct subarray, said control signals adjusting amounts of gain applied to detected signals; and

a master computer which receives said amplified detection signals from each of said plurality of slave computers, said master computer thereby forming an array by observing all outputs of each of the distinct subarrays to detect and track said aircraft therefrom by monitoring the detected signals received by all of the seismic and acoustic sensors, said master computer further observing a progression of the detected signals as seismic and acoustic signatures of aircraft strike sensors in the array and progress through the regular distribution over the geographic area of the terrain, said master computer thereby determining a direction from which said seismic and acoustic signals are produced with respect to said array to track said aircraft.

2. A detection system, as defined in claim 1 wherein said sensors are selected from a group consisting of:

geophones, microphones, absolute pressure sensors, gage pressure sensors, differential pressure sensors, and seismometers.

3. A detector system, as defined in claim 1, wherein said sensors are responsive to air coupled Rayleigh wave aircraft signatures with a frequency of 1.0-10 Hz and pressure waves with frequencies between 10-200 Hz.

4. A deflection system, as defined in claim 1, wherein each of said sensors includes:

a Wheatstone bridge circuit which supplies electrical power to said sensor;

an adjustable amplifier which is electrically connected to said Wheatsone bridge and said sensor, said amplifier providing an adjustable gain to said amplifier providing an adjustable gain to said detection signals so that they are received by one of the plurality of junction circuits, said adjustable amplifier thereby outputting said detection signals to one of the junction circuits;

a point-of-load unit which receives and adjusts electrical power to provide a stable supply of electrical power to said sensor through said Wheatsone bridge circuit; and

a means for adjusting the adjustable gain of said adjustable amplifer, said adjusting means receiving said control signals from one of the plurality of junction circuits and adjusting said adjustable gain in response thereto.

5. A detection system, as defined in claim 4, wherein each of said plurality of junction circuits comprises:

a power supply unit which is electrically connected with and supplies said electrical power to the point-of-load units of the sensors which are adjacent to each other in said regular distribution of the sensors over the geographical area;

a plurality of first input lines, each being electrically connected with and receiving the detection signals from the adjustable amplifier of one of the sensors;

a first set of amplifiers, each of which receives and applies a constant gain to the detection signals received from one of the plurality of first input lines, said set of amplifiers thereby outputting said amplified detection signals;

a plurality of first output lines, each of which receives and conducts amplified detection signals from one of the first set of amplifiers to one of the subarray circuits; and

a plurality of second input lines which receives and conducts said command signals from one of the subarray circuits to one of the adjusting means of one of the sensors.

6. A detection system, as defined in claim 5, wherein each of said subarray circuits comprise:

a plurality of third input lines, each connecting with and receiving said amplified detection signals from one of the first output lines from some of the plurality of junction circuits whose circuits are adjacent to each other in said regular distribution;

a second set of amplifiers, each receiving and boosting amplified detection signals from one of the plurality of third input lines to compensate for power losses over line transmission;

a plurality of second output lines, each receiving and conducting said amplified detection signals from one of the second set of amplifiers to one of the plurality of slave computers; and

a plurality of fourth input lines, each receiving said command signals from one of the slave computers and relaying it to one of the plurality of second input lines to allow the command signals to adjust the gain of each individual sensor.

7. A detection system, as defined in claim 6, wherein said slave computers each comprise:

a first microprocessor which receives digital detection signals and determines therefrom a progression of said Rayleigh and pressure wave aircraft signatures across the sensors in the subarray associated with said slave computer, said microprocessor thereby determining a subarray azimuth which indicates an azimuth to said aircraft with respect to said subarray;

an analog-to-digital converter which receives and processes said amplified detection signals from said second output lines from one of said subarray circuits to output digital detection signals to said first microprocessor;

a first digital bus which relays signals between said analog-to-digital converter and said microprocessor;

a first memory means which receives, stores and outputs said digital detection signals and said subarray azimuth from said first digital bus; and

a means for sending said digital detection signals and said subarray azimuth from said first memory to said master computer.

8. A detection system as defined in claim 7, wherein said master computer comprises:

a means for receiving said digital detection signals and said subarray azimuth from each of said slave computers;

a second digital bus which receives and relays said digital detection signals and each subarray azimuth received from said receiving means;

a second microprocessor which receives said digital detection signals and each subarray azimuth from said second digital bus, said second microprocessor detecting a presence of said aircraft by a presence of said digital detection signals, said second microprocessor locating said aircraft, by triangulating each subarray azimuth from the plurality of subarrays, said second microprocessor tracking said aircraft by repeatedly locating the aircraft, following its process as time progresses, and projecting its velocity and location, said second microprocessor thereby outputting signals indicating said aircraft'"'"'s detection, position and velocity; and

a second memory which receives and stores the output signals of the second microprocessor; and

a means for displaying the output signals of the second microprocessor.