North Korean ICBM launch detected using GPS (opens in new tab)

While Russia and China don’t want to see North Korea collapse as existing nuclear powers they don’t especially want to see other countries acquire nuclear weapons.

Active support and collaboration came from Pakistan, Iran and Libya who were all trying to develop nuclear weapons of their own.

https://rusi.org/explore-our-research/publications/commentar...

Google "aq khan pakistan north korea"

https://www.google.com/search?client=firefox-b-d&q=aq+khan+p...

https://en.wikipedia.org/wiki/Abdul_Qadeer_Khan

Yes there was a great deal of outside help with their enrichment and weapons design.

Both nuclear weapons and ballistic missiles are technologies from the 1940's.

They don't need outside help.

Remember that it took about 10 years for North Korea to go from it's first nuclear weapons test (which fizzled) to something that's probably a deliverable nuclear weapon, and they had spent decades before that to get to the first test. Nuclear weapons require great precision but they're not especially complicated devices. Any nation state, even the very poorest, should have no difficulty designing a nuclear weapon. It's the refinement of the design and the acquisition of the materials that is difficult, and even then the challenge is more in doing it clandestinely. Even then, the cost of the manhattan project, which not only developed two different nuclear weapons in 4 years, but also discovered a lot of the basic underlying physics from scratch, all in secret and with 1940s era equipment cost about $23 Billion adjusted for inflation. Similarly, the development contract for first American ICBM cost about $4 Billion in todays dollars. North Korea benefits from decades of scientific and technological advancement since that time, and it doesn't cost much to employ someone when you can throw their family into a camp, but even if we assume that it nevertheless would cost them as much to develop such technologies, over the course of 30 years that still represents a reasonably small fraction of North Korea's GDP. North Korea's long history of failures are pretty clear evidence that they were not given the design and manufacturing capability necessary to produce working nuclear weapons or missile systems. While no doubt there has been communication with other state actors over the decades, the idea that they are receiving active support is not at all supported by evidence, and indeed the embarrassingly long development time implies that either there is a great deal of incompetence in the development effort, active sabotage, or likely both.

GPS signals go through the ionosphere on their way from the satelites. The ionosphere causes distortions in the signal. If you want to achieve the best navigational accuracy you need to account for these distortions.

These distortions are not constant. They change from time to time. There are many different ways to account for them. One of the most accurate solution is to keep a GPS receiver on a well known location. Since you know that this receiver haven’t moved you can use the signal measured to estimate the parameters of the ionosphere between that station and the satelite.

Normally these signals are used to correct GPS navigational solutions. You take the closest station to your moving receiver and assume that whatever way the ionosphere was distorting for that station will do the same for your receiver too. This is valuable so there are network of such GPS stations in a lot of places.

Here they use the data collected by these stations differently. Instead of correcting a navigational solution they visualise the measured state of the ionosphere as seen by a bunch of these stations.

Section 2.1 in their linked paper (https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...) gives some clues. I think this is what's going on:

GPS receivers work by figuring out how far away they are from a number (>3) of GPS satellites. The receiver knows where the GPS satellites are (since the satellites broadcast their orbit parameters) so if a receiver knows how far it is from several satellites it can work out where it is itself.

Now, as the GPS satellite signals travel through Earth's atmosphere, they can be slowed down by different atmospheric effects. A slower signal will cause the receiver to think it's farther away from a satellite than it really is, so the receiver might estimate that it's position has changed a little bit. However, if you know the receiver's position hasn't change (maybe it's fixed in place to a big rock), then you can attribute the receiver's measured "change in position" to a change in atmosphere characteristics.

In this paper, they seem to have lots of fixed GPS receivers all over the place. By looking at all of them together, they can make a sort of map of the atmosphere characters in a part of the sky that's affected by rocket launches. The authors see these big ripples emanating from a Falcon Heavy launch in the US and this tweet shows those same ripples emanating from a launch site in North Korea.

Fun house mirrors are curved and distort your reflection.

Some fun house mirrors are flexible so they can get pushed or pulled which will make you look taller or shorter or fatter or skinnier than you know you are.

By observing the difference between how you appear compared with how you are; you can learn something about how the flexible mirror is being curved.

How this works in the fun house is there is you the mirror and LIGHT.

Both you and the light are well known and easy to predict; light will travel straight(ish) and you will not suddenly become very very short, so the thing that is changing your appearance is the flexible mirror.

In the GPS rocket case, the GPS satellites are the illuminating source corresponding to the light in the room sending out radio (electromagnetic radiation same as light just at longer wavelengths)

The ground station GPS receivers correspond to your eyes (they know what they *should* see).

The earth's ionosphere corresponds to the flexible fun house mirror.

taken together, the same way you could tell if something we can't see behind the mirror flexed it, the author of the post showed they can tell if, when and where an unannounced rocket goes through the ionosphere.

I don't think I could explain it to a small child, given that I don't have a great understanding of it myself. But here's what I could scrape together based on a linked paper[1]:

You use GPS receivers to detect ionospheric disturbances. Ionosphere, coming from the word "ionized", means it consists of charged particles, positive or negative. (Missile) exhaust is mainly neutral molecules, creating a "hole". These ionospheric holes can be detected through the Faraday Effect[2]. By measuring the Faraday rotation of radio signals (like GPS), you can detect these holes. I think this is similar to how polarized light 3d cinema systems work, except it's the radio spectrum instead of light.

[1] https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...

[2] https://en.wikipedia.org/wiki/Faraday_effect

As you walk past a school you yell with your voice, your friend nearby knows what you sound like but he hears you differently because your voice also bounces off the school wall. He adjusts the sound based on what you should sound like, the leftover bit is the shape of the wall.

You can figure out if someone moved a brick (or launched a missile) because your voice changes when it reaches your friend and he needs to apply a new change to get your voice back.

We can see the signal changes the rocket causes to the ionosphere and know that it's happened.

They don’t really seem to have a detector. They have a thing which makes visualisations, and it seems it should be possible to build a detector on top of that, but that doesn’t seem to be done yet.

The second tweet in the linked thread links to the paper which inspired them:

https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201...

> who insist on putting their code into the public domain

You say that as if there is something wrong with that.

If you follow the thread, there’s a link to https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/201... which contains this introduction:

======== It is widely recognized that rocket launches can be an anthropogenic source to trigger traveling ionospheric disturbances (TIDs) by generating acoustic-gravity waves (Afraimovich et al., 2002; Arendt, 1971; Bowling et al., 2013; Calais & Minster, 1996; Chou et al., 2018; Ding et al., 2014; Kakinami et al., 2013; Li et al., 1994; Lin et al., 2014; Lin, Chen, et al., 2017; Lin, Shen, et al., 2017; Noble, 1990). The rocket-induced long-distance propagating TIDs associated with shock/ducted gravity waves and internal gravity waves were observed by using Arecibo incoherent scatter radar (Noble, 1990) and ground-based Global Positioning System total electron content (TEC) observations (Calais & Minster, 1996). Lin, Shen, et al. (2017) first reported the rocket-induced shock waves and concentric TIDs (CTIDs) subsequently using Global Positioning System TEC over California-Pacific region. They suggested that the CTIDs are the manifestation of concentric gravity waves that were originated from the mesopause region. ====

The effect seems to be proven quite a while ago. Using GPS receivers to make that widely accessible seems to be new, but I honestly doubt that military intelligence would rely on that - I’m confident they have more direct methods to detect launches such as (radar) satellites.

Ham radio is actually where you’ll find a lot on the subject. “Band conditions” are determined by the amount of ionospheric disturbance present. For example, meteors entering the atmosphere produce a disturbance that can reflect radio—there are ham radio techniques that exploit this to communicate.