
A plan to turn the atmosphere into an enormous sensor - noir-york
https://www.economist.com/science-and-technology/2020/06/11/a-plan-to-turn-the-atmosphere-into-one-enormous-sensor
======
nchase
From the article:

 _The first 27 months of the programme will be dedicated to understanding the
science behind ripples in both the ionosphere and the electrically neutral
atmosphere below it, and then building computer simulations of what is going
on. These will be tested to see if they can replicate accurately effects seen
in the past._

 _Once the team have a better understanding of the basic science, they will
proceed to the second stage: field trials. This will involve three tests at
three-month intervals in which researchers attempt to locate pertinent events,
such as storm cells, mining operations and earthquakes. If that works, the
project will then move on to matters of military interest by spying on missile
launches, tracking aircraft and even watching underground bunkers being dug.
The result, if all goes well, may be the world’s first true panopticon._

Hopefully they spend more time on the atmospheric stuff than the military
stuff. Exciting news, if the former.

~~~
SllX
Any sufficiently advanced technology will be purposed for military use. This
will be purposed for Intelligence and Reconnaissance use if it fills a niche
they need filled.

~~~
082349872349872
Having worked in remote sensing[1] in the distant past, every now and then I
still glance at the Wassenaar Agreement[2] to find out what today's fun stuff
may be.

[1] interplanetary on my part, but I have no illusions that our funders didn't
have further intraplanetary applications in mind. I was young and needed the
money.

[2] [https://www.wassenaar.org/app/uploads/2019/12/WA-
DOC-19-PUB-...](https://www.wassenaar.org/app/uploads/2019/12/WA-
DOC-19-PUB-002-Public-Docs-Vol-II-2019-List-of-DU-Goods-and-Technologies-and-
Munitions-List-Dec-19.pdf)

(as far as watching bunkers being dug, I'm pretty sure LIDAR already gives a
much cleaner signal)

~~~
SllX
Hey, that’s perfectly reasonable. No, the problem we have as a society is we
live in this kind of reality which is governed by this thing called physics,
and as our understanding of physics progresses, our ability to abuse the shit
out of it also progresses. Some things aren’t a matter of if, but when.

That PDF is a gold mine by the way.

> as far as watching bunkers being dug, I'm pretty sure LIDAR already gives a
> much cleaner signal

The proposed applications are probably nothing more than something to get the
ball rolling but can already be done very effectively today. I hesitate to be
overly skeptical because an atmospheric panopticon would probably have more
applications than they would imagine or dare to propose themselves.

------
nuccy
The atmosphere is also used as a detection medium for Imaging Atmospheric
Cherenkov Telescopes (IACTs) [1]. Very high energy (>tens GeV) photons,
electrons or nuclons hit atoms in the atmosphere and produce a cascade of
secondary particles, which move faster than the speed of light in the air
emitting Cherenkov light [2]. Flashes of this light are lasting for few
nanoseconds, so the cameras have nanosecond sampling time and are based on
photo multipliers.

There are many such telescopes around the world: MAGIC (2 telescopes), FACT
(1), HESS (5), Veritas (4). The biggest assembly of such telescopes is
currently under construction - Cherenkov Telescole Array [3] with hundred of
telescopes in Paranal, Chile and 20 in La Palma, Canary Islands. One large
telescope with a mirror of 23m diameter is already operating [4].

[1]
[https://en.m.wikipedia.org/wiki/IACT](https://en.m.wikipedia.org/wiki/IACT)

[2]
[https://en.m.wikipedia.org/wiki/Air_shower_(physics)](https://en.m.wikipedia.org/wiki/Air_shower_\(physics\))

[3]
[https://m.youtube.com/watch?v=5gRHFQP_SjU](https://m.youtube.com/watch?v=5gRHFQP_SjU)

[4] [https://www.cta-observatory.org/lst-1_inauguration/](https://www.cta-
observatory.org/lst-1_inauguration/)

~~~
javawizard
This is fascinating, but:

> which move faster than the speed of light

Citation needed. I was of the understanding that this is impossible, and your
first two links provide no evidence to the contrary.

~~~
throwaway_pdp09
> which move faster than the speed of light in the air emitting Cherenkov
> light

Key words "in the air". As they can't go faster than C in this medium[0], they
are forced to slow down, and emit this lost kinetic energy as radiation - my
understanding.

Something a bit better, from
[https://en.wikipedia.org/wiki/Cherenkov_radiation](https://en.wikipedia.org/wiki/Cherenkov_radiation)

Cherenkov radiation is electromagnetic radiation emitted when a charged
particle passes through a dielectric medium at a speed greater than the phase
velocity of light in that medium. A classic example of Cherenkov radiation is
the characteristic blue glow of an underwater nuclear reactor.

[0] I realise this seems contradictory - they can't but for a short time they
are - I don't understand that either.

~~~
nuccy
Exactly, speed of light in the vacuum ( _c_ ) is the hard limit, only mass-
less objects can move that fast (e.g. photons). The refraction index ( _n_ )
tells you how fast light moves in a medium. It is defined as _n=c /v_, where
_v_ is the speed of light in the medium. That's why (and also because of
internal reflections) the speed of light in the fiber optics is not quite
reaching _c_ [0], and with inter-satellite communication Starlink may provide
lower latency than the one using landline fiber optics channels. For air
refraction index is very close to 1 [1], but not quite, at 10km altitude _n=_
1.0001, which is 99.99% of _c_. For example a proton with an energy of 1TeV
(Tera electron-volt, 1x10^12 eV) is moving 99.999956% speed of light in vacuum
[2], and we see protons up to 5x10^19 eV reaching 99.99999999999999999998% of
_c_ [3]. Even "low" energy protons (tens of GeV) hitting molecules of air can
kick out electrons, which, due to being lighter, can move faster than the
initial protons and emit Cherenkov radiation.

[0] [https://www.quora.com/What-is-precisely-the-speed-of-
light-i...](https://www.quora.com/What-is-precisely-the-speed-of-light-in-
fiber-optics)

[1]
[https://www.researchgate.net/profile/Dmytro_Vasylyev/publica...](https://www.researchgate.net/profile/Dmytro_Vasylyev/publication/330553517/figure/fig9/AS:718074235863040@1548213647171/Temperature-
pressure-and-refractive-index-as-functions-of-altitude-Dots-represent-the.png)

[2]
[https://uspas.fnal.gov/materials/10MIT/Review_of_Relativity....](https://uspas.fnal.gov/materials/10MIT/Review_of_Relativity.pdf)

[3]
[https://en.wikipedia.org/wiki/Greisen–Zatsepin–Kuzmin_limit](https://en.wikipedia.org/wiki/Greisen–Zatsepin–Kuzmin_limit)

------
ur-whale
[http://archive.is/IJD98](http://archive.is/IJD98)

