Detection Rate Improvements Through Understanding and Modeling Ocean Variability
Navy STTR 2018.A - Topic N18A-T002 NAVAIR - Ms. Donna Attick - donna.moore@navy.mil Opens: January 8, 2018 - Closes: February 7, 2018 (8:00 PM ET)
TECHNOLOGY
AREA(S): Battlespace ACQUISITION
PROGRAM: PMA 290 Maritime Surveillance Aircraft OBJECTIVE:
Improve the detection rate of targets through the understanding and modeling of
ocean variability resulting in a robust model that can eventually be
incorporated into mission planning software. DESCRIPTION:
Variance in transmission loss (TL) between an acoustic source and a target can
have a profound effect on detection performance using low-frequency (50 – 3000
Hz) active acoustics. This variance has often been observed in real data, but
is not well-captured in modeling, simulation, or post-test reconstruction.
While ambient noise or reverberation is a prominent contributor to signal
excess in the sonar equation, it cannot be controlled, is easily measured, and
has shown reproducibility between like measurements. However, unlike ambient
noise, TL has shown a large variance between like measurements. This poor
repeatability of measurements is especially challenging where detections are
made at the threshold (i.e., close to or at 0 signal excess). If this
variability can be well understood in terms of the ocean environment then it
would allow for a more accurate prediction that will aid test planning as well
as post-test reconstruction. PHASE
I: Analyze a series of Government-furnished acoustic data sets with ducted
propagation and provide a preliminary reconstruction of the acoustic
environment. During the Phase I Option, if awarded, develop a concept for a
surface duct model that can predict the observed acoustic environment
variability. With the use of highly sampled (many sound speed profiles) data
sets and hind cast ocean model data, further develop the model to provide increasingly
accurate sensor level outputs. The Phase I effort will include plans for a
Phase II. PHASE
II: Expand the model to include bottom returns. Bottom loss and bottom
reverberation are currently treated as two separate quantities: Bottom Loss as
part of TL, and reverberation is fitted by Lambert’s Law with variable
Mackenzie's coefficient. In reality, however, the two quantities are related
by geo-acoustics of the bottom and should be treated in a uniform manner. The
goal is to generate sensor-level signals which are from the bottom return.
This allows consistent TL and reverberation treatment, rather than artificially
separating them into reflection and scattering. At the end of the phase the
developed model can be employed as a sensor-level simulator that may mimic real
system performance. PHASE
III DUAL USE APPLICATIONS: Verify and validate the model. Integrate it into an
engineering version of a tactical decision aid, such as the Multistatics
Planning Acoustics Toolkit (MPAcT). The developed technology will benefit the
oceanographic community to include academic/research and oceanographic mission
planners, as well as the oil exploration industry. REFERENCES: 1.
Acoustic transmission in an ocean surface duct, performed by U.S. Navy
Electronics Laboratory, San Diego, California, and analyzed by Arthur D Little,
Inc., Dept. of the Navy, Naval Ship Systems Command, NO bsr – 93055, Project
Serial Number SF 101-03-21, Task 11353, Nov 1966. https://ia600500.us.archive.org/12/items/acoustictransmis00usna/acoustictransmis00usna.pdf 2.
Porter, M. B., Piacsek, S., Henderson, L., and Jensen, F. B. “Surface duct
propagation and the ocean mixed layer.” Oceanography and Acoustics Prediction
and Propagation Models, 1st ed., edited by A. Robinson and D. Lee (AIP, New
York, 1993), pp. 50-79. ISBN: 1563962039. http://trove.nla.gov.au/work/11481132?selectedversion=NBD10719975 3.
Jensen, F. B., Kuperman, W. A., Porter, M. B., and Schmidt, H. Schmidt.
“Computational Ocean Acoustics”, 2nd ed. (Springer, New York, 2011), pp.
494-495. http://www.springer.com/us/book/9781441986771 4.
Vadov, R. “Acoustic propagation in the subsurface sound channel.” Acoustical
Physics, January 2006, 52, pp, 6–16. https://link.springer.com/article/10.1134/S1063771006010027 5.
Mellen, R. & Browning, D. “Attenuation in surface ducts.” The Journal of
the Acoustical Society of America. 63, pp, 1624-1626. http://asa.scitation.org/doi/abs/10.1121/1.381859 6.
Weston, C. Esmond, and Ferris, A. Ferris. “The duct leakage relation for the
surface sound channel.” The Journal of the Acoustical Society of America. 89,
pp. 156–164 (1991). http://asa.scitation.org/doi/abs/10.1121/1.400521
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