Acoustic multifunctional standard calibration method
View Patent ↗A method for using a deployable, small package acoustic transmitter device is taught, which serves as a standard acoustic source for on-vessel, in-mission field calibration purposes. The method involves deploying an acoustic transmitter device underwater to provide a predefined acoustic energy source for sonar array detection as well as periodic time-coded acoustic signal pulses for tracking and calibration of passive ranging.
1. An acoustic transmitting method, comprising:
deploying an acoustic transmitter device, capable of transmitting and recording a plurality of acoustic signals, from a marine-vessel, wherein said acoustic transmitter device is deployed underwater at a predetermined distance from said marine-vessel and is contained in an expendable package;
providing at least one predefined standard acoustic signal for underwater acoustic energy transmission by said acoustic transmitter device;
providing a periodic acoustic signal pulse with encoded information for underwater acoustic energy transmission by said acoustic transmitter device;
transmitting said at least one predefined standard acoustic signal to ensonify at least one acoustic receiver joined to said marine-vessel, wherein said at least one predefined standard acoustic signal is transmitted from a predefined depth at a specified start time for a specified period of time;
changing the depth of the acoustic transmitter device during a transmit operation at a selectable rate;
recording a plurality of acoustic signal data, including acoustic signal data projected by said marine-vessel, by means of said acoustic transmitter device; and
controlling said acoustic transmitter device by a remote controlled trigger signal and alternately by a plurality of preset conditions.
2. The acoustic transmitting method of claim 1 further comprising:
transferring and recording a plurality of acoustic signal data to and from the acoustic transmitter device prior to deploying said acoustic transmitter device.
3. The acoustic transmitting method of claim 1 wherein the acoustic transmitter device is capable of terminating its performance by a self destruct after completion of at least one acoustic signal transmission.
4. The acoustic transmitting method of claim 1 wherein the acoustic transmitter device is capable of floating for retrieval after completion of at least one acoustic signal transmission.
5. The acoustic transmitting method of claim 1 wherein the encoded information comprises time information from a clock that is synchronized with a receiver array clock.
6. The acoustic transmitting method of claim 1 wherein deploying the acoustic transmitter device is accomplished through the use of a launching means.
7. The acoustic transmitting method of claim 1 further comprising:
linking the acoustic transmitter device to a surface buoy antenna; and
receiving an electric radio frequency signal and a plurality of global positioning satellite data from the surface buoy antenna to the acoustic transmitter.
8. The acoustic transmitting method of claim 1 further comprising:
calibrating an on-vessel acoustic array using standard methods, based on the information transmitted by the acoustic transmitter device and received at the on-vessel acoustic array.
9. The acoustic transmitting method of claim 5 further comprising:
transmitting a predefined continuous acoustic source signal from the acoustic transmitter device;
transmitting at least one periodic time coded acoustic signal from the acoustic transmitter device;
receiving a plurality of timing information from the at least one periodic time coded acoustic signal by means of a receiving array having N elements joined to said marine vessel;
decoding the plurality of timing information from the at least one periodic time coded acoustic signal by said receiving array through signal processing means implemented on a computer;
calculating the duration that the at least one time coded acoustic signal traveled in the water by means of said computer; and
calculating an acoustic ray path slant range by means of said computer.
10. The acoustic transmitting method of claim 9 wherein calculating the duration that the at least one time coded acoustic signal traveled in the water is accomplished according to
{
d
->
i
=
r
->
s
-
r
->
i
t
i
=
d
->
i
/
c
τ
ij
=
(
d
->
i
-
d
->
j
)
/
c
i
,
j
=
1
,
2
,
…
,
N
,
wherein c is the propagation sound speed of the water, t i and τ ij are the signal travel time to the ith array and the difference of the propagation time between ith and jth receiving arrays respectively.
11. The acoustic transmitting method of claim 9 wherein calculating an acoustic ray path slant range further comprises:
calculating the exact coordinates of x s , y s and z s for the acoustic transmitter device subject to the following N
governing
equations
{
d
->
1
=
(
x
S
-
x
1
)
2
+
(
y
S
-
y
1
)
2
+
(
z
S
-
z
1
)
2
d
->
2
=
(
x
S
-
x
2
)
2
+
(
y
S
-
y
2
)
2
+
(
z
S
-
z
2
)
2
⋮
d
->
i
=
(
x
S
-
x
i
)
2
+
(
y
S
-
y
i
)
2
+
(
z
S
-
z
i
)
2
⋮
d
->
N
=
(
x
S
-
x
N
)
2
+
(
y
S
-
y
N
)
2
+
(
z
S
-
z
N
)
2
,
in a homogeneous medium.
12. The acoustic transmitting method of claim 9 further comprising:
calibrating the position of the ith sensor having array coordinates x i , y i and z i according to the following iteration of equations implemented on said computer,
{
τ
1
,
i
=
d
->
1
-
d
->
i
c
=
1
c
(
(
x
S
-
x
1
)
2
+
(
y
S
-
y
1
)
2
+
(
z
S
-
z
1
)
2
-
(
x
S
-
x
i
)
2
+
(
y
S
-
y
i
)
2
+
(
z
S
-
z
i
)
2
)
τ
2
,
i
=
d
->
2
-
d
->
i
c
=
1
c
(
(
x
S
-
x
2
)
2
+
(
y
S
-
y
2
)
2
+
(
z
S
-
z
2
)
2
-
(
x
S
-
x
i
)
2
+
(
y
S
-
y
i
)
2
+
(
z
S
-
z
i
)
2
)
⋮
τ
i
-
1
,
i
=
d
->
i
-
1
-
d
->
i
c
=
1
c
(
(
x
S
-
x
i
-
1
)
2
+
(
y
S
-
y
i
-
1
)
2
+
(
z
S
-
z
i
-
1
)
2
-
(
x
S
-
x
i
)
2
+
(
y
S
-
y
i
)
2
+
(
z
S
-
z
i
)
2
)
τ
i
-
1
,
i
=
d
->
i
+
1
-
d
->
i
c
=
1
c
(
(
x
S
-
x
i
+
1
)
2
+
(
y
S
-
y
i
+
1
)
2
+
(
z
S
-
z
i
+
1
)
2
-
(
x
S
-
x
i
)
2
+
(
y
S
-
y
i
)
2
+
(
z
S
-
z
i
)
2
)
⋮
τ
N
,
i
=
d
->
N
-
d
->
i
c
=
1
c
(
(
x
S
-
x
N
)
2
+
(
y
S
-
y
N
)
2
+
(
z
S
-
z
N
)
2
-
(
x
S
-
x
i
)
2
+
(
y
S
-
y
i
)
2
+
(
z
S
-
z
i
)
2
)
,
where the N−1 governing equations are available for three unknown solutions of x i , y i and z i , and i can vary from 1 to N.