detecting tunnels by mapping gravity

Eugen Leitl eugen at leitl.org
Mon Mar 16 11:14:48 PDT 2009


http://www.theregister.co.uk/2009/03/16/darpa_tunnel_detector/

DARPA to build nothingness detector for tunnel sniffing

Bottom falls out of subterranean-lair market

By Lewis Page

Posted in Physics, 16th March 2009 13:07 GMT

Renowned US military tech bureau DARPA has issued a request for an
ultrasensitive gravity-measuring instrument which could be mounted in a low
flying aircraft and detect underground tunnels.

The project, known as Gravity Anomaly for Tunnel Exposure (GATE), was
formally announced on Friday. In essence, it will detect an absence of
underground mass - dirt, rock or whatever - by picking out the tiny drop in
the local gravity caused by the missing stuff:

    The explicit action of digging tunnels introduces a void into the
subsurface geology. Gravity gradiometers measure tiny spatial variations in
the pull of gravity caused by these underground voids. The GATE objective is
to develop, integrate, and demonstrate a prototype airborne gravity
gradiometer system which is capable of detecting the mass deficit of a void
in the presence of geological and topological variability.

A nothingness detector, in other words, able to perceive the hole rather than
the doughnut. But in this case the wacky research agency seems to believe
that the current state of the art in gradiometer systems is close to being
discriminating enough to do the job already. What's needed is the ability to
tune out all the noise and clutter from natural geological features, the
carrying aircraft's vibration and so forth.

"This is not expected to be a sensor technology development activity, but
rather focus on adapting the existing technology to GATE application," says
the solicitation document (pdf)
(https://www.fbo.gov/download/0bb/0bbb4887d04b404e5648dfbb4a743f44/GATE.pdf).

DARPA thinks that it should be possible to fit a ground-penetrating grav
spyeye and all necessary processing on board the carrying aircraft, which can
be manned or unmanned. There shouldn't be any need to pipe massive amounts of
sensor data back to a ground station for analysis, either. The final
prototype, according to the solicitation, should offer "the ability to detect
the presence of a tunnel" and "the ability to image skeletal outline of a
tunnel network".

As to what you might use the GATE tunnel-sniffer gear for, DARPA does offer a
hint:

    To address the more immediate underground tactical threats, the Gravity
Anomaly for Tunnel Exposure program will focus on border and perimeter
breaching tunnels.

There have been a few border-breaching tunnels in the news
(http://news.bbc.co.uk/1/shared/spl/hi/middle_east/04/gazas_tunnels/html/1.stm)
lately, as it happens. 





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