

A new way to detect secret nuclear tests: GPS - Sandman
http://www.thebulletin.org/web-edition/op-eds/new-way-to-detect-secret-nuclear-tests-gps

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wickedchicken
"GPS might at first seem like an unlikely source for nuclear test detection."
Actually, it makes total sense. So much sense that the creators of GPS put
sensors in the satellites to do this...

"GPS satellites carry a set of nuclear detonation detectors consisting of an
optical sensor (Y-sensor), an X-ray sensor, a dosimeter, and an
electromagnetic pulse (EMP) sensor (W-sensor), that form a major portion of
the United States Nuclear Detonation Detection System"
<http://en.wikipedia.org/wiki/Global_Positioning_System>

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mturmon
That's interesting, I did not know that.

The approach in the article is in fact quite novel, though.

They're actually detecting the shock wave in the atmosphere. Not even
something "easy" like the seismic shock wave.

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mturmon
This is a cool application of GPS radio occultation. For a simple overview,
see:

<http://www.atmo.arizona.edu/~kursinsk/GPS_RO_overview.htm>

The same idea has recently been used to improve weather forecasts for a few
years now (<http://en.wikipedia.org/wiki/GPS_meteorology>).

Differences in atmospheric gas density affect the propagation speed of the GPS
radio signal. Peering thru the edge of the atmosphere at the constellation of
GPS transmitters allows you to get a bunch of density/temperature profiles in
a way that's immune to some instrumental artifacts of other instruments.

One of the inventors of the idea formed a company to cooperatively launch
small satellites to do these retrievals:

<http://geooptics.com/?page_id=35>

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maaku
If the data is accurate enough to detect a kiloton blast deep underground,
what about conventional weapons on the surface? Could this be used to detect
and track the use conventional explosives deep inside the territory of
oppressive regimes?

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alex_h
Somehow I don't think this is the main sticking point preventing the US from
ratifying the nuclear test ban treaty, as the article seems to suggest.

~~~
caf
Page Van der Linden has posted the first two parts of a multipart series on
the domestic arguments around US ratification of the CTBT, if you're
interested:

[http://vanderlinden.armscontrolwonk.com/archive/205/secrets-...](http://vanderlinden.armscontrolwonk.com/archive/205/secrets-
in-the-sand) [http://vanderlinden.armscontrolwonk.com/archive/225/we-
shoul...](http://vanderlinden.armscontrolwonk.com/archive/225/we-should-
retain-the-option-to-test)

