[HN Gopher] North Korean ICBM launch detected using GPS
___________________________________________________________________
North Korean ICBM launch detected using GPS
Author : Pietertje
Score : 220 points
Date : 2022-11-27 12:22 UTC (10 hours ago)
(HTM) web link (twitter.com)
(TXT) w3m dump (twitter.com)
| H8crilA wrote:
| Isn't the ionosphere already past the burn-out phase of a
| ballistic missile? I.e. by the time the rocket gets there it is
| just a glorified harpoon. Or perhaps that doesn't matter as
| anything of this size travelling at this speed would cause
| detectable disturbance?
| krisoft wrote:
| Here is the code which generated the linked video:
| https://github.com/tylerni7/missile-tid
| ransom1538 wrote:
| I will avoid politics in this comment. But, is the current
| US/JP/SK plan to wait until NK gets a working ICBM with a nuclear
| warhead and hope he acts rationally?
| vkou wrote:
| Acquiring and developing nuclear weapons seems to be the most
| rational thing North Korea has done in a very long time.
|
| Neither the Iraq nor Ukraine conflicts would have happened if
| they were nuclear states.
|
| An armed society is a polite society, or so I've been told
| many, many times.
| tdeck wrote:
| Just to add a little context to this comment, the world's
| foremost nuclear power (the USA) runs live-fire exercises
| every year where its army practices invading North Korea.
| Under these circumstances, it's entirely rational for the NK
| government to develop nuclear weapons.
|
| If the US government really wanted to stop this, it could
| offer a good faith deal for disarmament involving some kind
| of reduction of sanctions or normalization of relations.
|
| Instead US politicians prefer to hypocritically hand-wring
| about other countries' nuclear development while maintaining
| a massive nuclear arsenal to threaten every other country,
| and while invading or bombing other countries on a regular
| basis. These are the actions that cause states to feel
| threatened enough to pour enormous resources into nuclear
| weapons development.
| avereveard wrote:
| Apparently only certain kind of states feel threatened. I
| wonder what the common thread is between them
|
| Oh right, it's the dictatorial megalomaniacs that spew anti
| western rethoric as distraction for their masses, that who.
|
| Truly evil, these USA are.
| tdeck wrote:
| By this logic Saudi Arabia should feel threatened. But
| Saudi Arabia is a US client state so it doesn't need to
| worry.
|
| Also, you completely ignored the part about the US
| practicing invading the country every year. Apparently
| that doesn't constitute a threat?
| avereveard wrote:
| Eh out of the schoolyard we're past "he whom hasn't fault
| may throw the first stone"
|
| And I don't coun't that many bullshit wars. The second
| invasion of Iraq, maybe Afghanistan. Lybia was, but it
| was France's bullshit war.
|
| Besides Usa has many allies and responsabilities, it's
| not that strange having them involved in many conflicts.
| yongjik wrote:
| > live-fire exercises every year where its army practices
| invading North Korea
|
| It's "practicing invading North Korea" in the same sense
| North Korea's missile tests are "practicing dropping nukes
| on America." It's a war practice, all options are on the
| table, with the hope that they won't be necessary.
|
| South Korea and the US had canceled the yearly joint
| exercise in 2019, hoping for a better relation with North
| Korea. It didn't work out - see https://en.wikipedia.org/wi
| ki/List_of_North_Korean_missile_t...
|
| The exercise resumed in 2022.
| tdeck wrote:
| > It's "practicing invading North Korea" in the same
| sense North Korea's missile tests are "practicing
| dropping nukes on America."
|
| The context here is extremely important. All of this (the
| invasion exercises, the missile tests, the Korean War)
| have taken place in the Korean peninsula. None of it has
| threatened the US homeland in a meaningful way.
|
| In addition, the exercises have been going on since 1997.
| That's a long time before any missile tests were
| conducted. If the DPRK (North Korea's name for its state)
| had been testing nukes from Cuba in 1997 I'd feel
| differently. But note that even dropping live bombs on
| other countries is something the US gets to do without
| starting a war because the US military is so powerful.
| Very few other countries operate that way and North Korea
| certainly isn't one of them.
| swagasaurus-rex wrote:
| Who helped North Korea acquire nuclear weapons? Was it a wise
| choice? Only time will tell.
| [deleted]
| ravenstine wrote:
| They've launched them in the last year. This is really nothing
| new.
|
| https://www.youtube.com/watch?v=vEgE4R_6fLU
| rafael09ed wrote:
| That question implies that they couldn't land a nuke in Japan
| or South Korea currently. I think their current rockets have
| that capability.
| germinalphrase wrote:
| They do - but that's only part of the risk. The logistics
| around nuke delivery is more complicated (or course).
|
| For the interested: "Arms Control Wonk" podcast and blog with
| Jeffery Lewis and Aaron Stein are good resources.
| mikeyouse wrote:
| They very likely already have that.. they've detonated >50kt
| nukes and have mobile ICBM launchers that have demonstrated
| rockets with thousands of miles of range.
|
| They could almost certainly detonate a nuclear weapon in Korea
| or Japan. I'd put even odds on a strike on Guam, but probably
| not quite capable of hitting Western US.
| dontbenebby wrote:
| >they've detonated >50kt nukes
|
| Are you sure? Didn't they also detonate a buncha TNT to make
| it look like a nuke blast once?
|
| (A weird thing to lie about.)
| hamandcheese wrote:
| > A weird thing to lie about.
|
| Having the world believe you have nukes is nearly as
| valuable as actually having them.
| cfraenkel wrote:
| More valuable, in any rational sense of the term. Having
| them without anyone believing that you have them is more
| or less useless. Their only purpose is deterrence (unless
| you have a death wish for your population, and there are
| easier methods available if that's your 'use case')
| IAmGraydon wrote:
| I believe that's his point.
| NikkiA wrote:
| They've put stuff in orbit before, so I'd wager they could
| hit the continental US, but probably without any accuracy
| beyond maybe picking a state.
| kortilla wrote:
| They haven't gotten anything to orbit with the weight of an
| atomic bomb with the proper shielding to handle re-entry.
| NikkiA wrote:
| Kwangmyongsong-4 was apparently 200Kg, which is actually
| just about enough.
| jasonwatkinspdx wrote:
| NK _has_ a working ICBM with a nuclear warhead today. It 's
| already done. The time to stop it was back in the 90s.
| rich_sasha wrote:
| Do we know they can make warheads small enough to fit on
| ICBMs? I always understood that is quite difficult.
|
| AFAICT we know they have blown up stationary nukes and shot
| out inert ballistic missiles.
| FpUser wrote:
| They might ask Russia for help
| bismuthcrystal wrote:
| Lets speculate a little bit for argument sake. Take this
| with a grain of salt because I am not a specialist, just a
| information hoarder.
|
| Lets put miniaturization aside and focus on another
| aspects, which i judge will be more critical.
|
| The warhead must survive mechanical stress of launch and
| reentry, and thermal stress at reentry. The question is:
| can it be designed only with computers and public
| knowledge? They could build small hypersonic wind tunnel to
| collect data and simulate the rest.
| samus wrote:
| Even assuming it's not already too late for that: what could
| they do? NK is already sanctioned to the max. And the few
| leavers that they can still pull probably wouldn't be enough to
| stop them at this point. And them being so close to China and
| SK makes any direct military action against them likely to
| trigger WW3.
| retrac wrote:
| If JP/SK/US did decide on military action against North
| Korea, I would expect China to stand back, close their
| border, and do nothing but make loud protest noises. They're
| not keen on sharing a border with a US client state. They're
| also not keen on a rogue North Korea with nukes.
|
| The main issue is that, even without nuclear weapons, North
| Korea has enough conventional arms, including chemical
| weapons, to cause horrific damage to South Korea. Seoul's
| entire urban area is within artillery range of the DMZ. I've
| seen estimates of varying credibility but most experts speak
| of hundreds of thousands of deaths on the first day of
| shelling, if a full-scale war broke out on the Korean
| peninsula.
| FpUser wrote:
| >"If JP/SK/US did decide on military action against North
| Korea"
|
| NK is no longer part of NPT. Would not this war be illegal?
| How does it correspond with "we are the nation of laws"?
|
| >"I would expect China to stand back"
|
| And what if it does not?
| retrac wrote:
| I know quite well, as you probably do, that international
| law has zero bearing on the military decisions made by
| the USA in terms of its interests. Yes, it'd be illegal,
| unless the UN Security Council gave its blessing. Just
| like the second Gulf War was illegal. That has never
| stopped the US before.
|
| > How does it correspond with "we are the nation of
| laws"?
|
| It does not. The United States government rejects the
| idea it is restricted by international law on these
| matters.
|
| As for South Korea, it can argue it's an internal
| domestic matter.
| FpUser wrote:
| >"That has never stopped the US before"
|
| I know this much. My question was largely rhetorical.
| colechristensen wrote:
| "Illegal war" is just a phrase to make political noise
| about military action you don't like.
|
| There are treaties, not laws, and no body to actually
| enforce laws, it's just diplomacy. General practices are
| agreed upon but they're basically just loose agreements.
| bmitc wrote:
| I have been wondering: is North Korea an example of sanctions
| not working or having the opposite effect? By sanctioning
| North Korea to the moon and back, they have no other choice
| but to bottle up, tighten the hatches, take an authoritarian
| stance, deal with people willing to do deals under the table,
| and search for ways to strike back. Since they don't have the
| capability of building a traditional military force, they go
| for the biggest thing they can: nuclear missiles. Meanwhile,
| their people starve and suffer.
|
| Are there not alternative policies that would work a little
| better? North Korea just seems like a cornered badger and
| will continue to act like one. If you "opened" up the country
| by reducing some sanctions, it seems they'd have to adapt to
| be more civilized. These are more questions than statements.
| avereveard wrote:
| We tried detente and appeasement various times and at
| various stages, it usually doesn't work
| bmitc wrote:
| What is the end game with North Korea though? It seems
| the only options are:
|
| * It collapses on its own or there's an internal
| revolution or coup. This would be a mess though because
| of the whole China, Russia, South Korea claims probably.
|
| * It does something drastic and attacks and then gets
| invaded. That also seems a mess because now it's China,
| Russia, South Korea, and the U.S. and maybe Japan,
| depending on who it attacks.
| noobhack wrote:
| K
| amelius wrote:
| I'd like to see the amount of false positives/negatives, rather
| than just data of one day.
| krisoft wrote:
| 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.
| beardyw wrote:
| Is it possible someone could explain as if to a small child what
| data can be collected from GPS which shows this effect. I don't
| understand.
| chmod775 wrote:
| 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
| krisoft wrote:
| 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.
| morcheeba wrote:
| Good explanation.
|
| A simple GPS receiver will have a generic mathematical model
| for the ionosphere and use that as a good guess. More
| advanced ones can measure the delay directly.
|
| The ionosphere affects different frequencies differently, so
| the GPS satellites transmits additional signals at different
| frequencies. By measuring the phase of these signals (L1 and
| L2), the math can be done to get a better estimation of the
| delay caused by the ionosphere between each satellite and the
| receiver. Those are the dots we're seeing on this animation.
| (GPS also uses the L2 signal to transmit encrypted
| information that lets military receivers get a better fix
| than civilian receivers).
|
| more info: https://www.e-education.psu.edu/geog862/node/1715
| cm2187 wrote:
| But what are the moving dots in the animation? Planes,
| satellites? (seems to move like neither).
|
| GPS being a military technology, I presume those fixed gps
| stations are only located in US-friendly countries. You
| wouldn't get that adjustment if you are flying over Russia or
| China, or any ocean. How much of an error in absolute
| distance are we talking about here? A few cm or meters or a
| km?
| krisoft wrote:
| > But what are the moving dots in the animation? Planes,
| satellites?
|
| Neither. The stations are in Japan. Imagine a line going
| from each of those stations to the satellite. Where this
| line crosses the ionoshpere that spot is what is measured.
| That is what you have information about. Those spots are
| the dots.
|
| So you basically see the arc of the Japanese islands
| projected up towards each satelite which is visible from
| these stations. When the satelite is low on the horizon
| this projection seems to move fast, and when it is near the
| zenit it seems to move slow. This is what you are seeing
| with the dots.
|
| Their location is calculated here:
| https://github.com/tylerni7/missile-
| tid/blob/main/tid/tec.py...
|
| "Given a receiver and a satellite, where does the line
| between them intersect with the ionosphere?"
|
| And then that is called here:
| https://github.com/tylerni7/missile-
| tid/blob/00c5fd25e2ab3c2...
|
| "The locations where the signals associated with this
| connection penetrate the ionosphere."|
| jwsteigerwalt wrote:
| This explanation helps understand the video.
| layer8 wrote:
| What are the stations/receivers? Is this crowdsourced
| data?
| williamscales wrote:
| They have a GPS receiver in a fixed, known location. They
| measure the received signal and from the variations infer
| corrections for ionospheric effects. They are part of the
| GPS network.
|
| [0] https://en.wikipedia.org/wiki/GNSS_augmentation
| danbruc wrote:
| _But what are the moving dots in the animation?_
|
| I would guess the moving dots are fixed GPS receivers, or
| more precisely the intersections of lines between fixed GPS
| receivers and moving GPS satellites with a sphere around
| Earth representing the ionosphere. If you look at the shape
| of the moving clusters, some look like Japan.
| squarefoot wrote:
| > One of the most accurate solution is to keep a GPS receiver
| on a well known location.
|
| I wonder if a network of connected devices with a GPS-
| disciplined SDR receiver and a regular GPS one could work
| both as this project does plus as passive radar like the
| software that was recently taken down. The purpose would be
| to have much wider coverage along with redundancy and error
| correction.
| toomuchtodo wrote:
| Such networks exist and make their data public. I think the
| equivalent you're looking for is like LightningMaps, where
| there is real time reporting of observations instead of
| having to process recorded data to look back in time?
|
| https://geodesy.noaa.gov/CORS_Map/
|
| https://www.e-education.psu.edu/geog862/node/1830
|
| https://learn.sparkfun.com/tutorials/how-to-build-a-diy-
| gnss...
| colechristensen wrote:
| I worked on something like this in university. GPS bistatic
| radar. Two SDR frontends with directional antennas pointed
| in different directions to do various remote sensing,
| ranging, and other things.
|
| The GPS network is essentially kept up to date with a few
| ground stations. The ground station is a source of truth
| that is used to send correction updates to the
| constellation periodically which are sent to all receivers.
| thatcherc wrote:
| Section 2.1 in their linked paper (https://agupubs.onlinelibrar
| y.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.
| jvm___ wrote:
| 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.
| tejtm wrote:
| 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.
| perihelions wrote:
| Related: last month's [0] gamma-ray burst also had interesting,
| measurable effects on the ionosphere,
|
| https://gcn.gsfc.nasa.gov/gcn3/32744.gcn3 ( _" GRB221009A:
| Detection as sudden ionospheric disturbances (SID)"_)
|
| https://www.qsl.net/df3lp/grb221009/KLM_grb221009a_magnitude...
| (from the above link)
|
| http://abelian.org/vlf/grb221009a-DHO.png
|
| http://abelian.org/vlf/grb221009a-NAA.png
|
| http://abelian.org/vlf/grb221009a-NSY.png
|
| [0] https://news.ycombinator.com/item?id=33215572 ( _" Record-
| breaking gamma-ray burst possibly most powerful explosion ever
| recorded"_)
|
| This was detected with VLF radio, but I wonder if this kind of
| event also has an effect on GPS signals? The time-of-arrival of
| astrophysical gamma rays isn't uniform across the earth.
| gregfjohnson wrote:
| What I wonder about is all of the technologies that go into
| ICBM's with nuclear weapons. My layman's guess is that there is
| active support and collaboration of the NK nuclear program from
| outside. North Korea is a headache for the US and other western
| powers, one more thing to consume policy bandwidth and military
| preparedness. This would seem to be in the interests of China and
| Russia, and perhaps others. I don't worry too much about the
| threats that periodically emanate from North Korean; if they
| start to exceed their utility from the perspective of China and
| Russia, the needed resources to maintain a viable nuclear program
| can be quickly shut off. I do hope that I will live to see a
| "1989" moment in which the North Korean regime is overthrown, and
| relegated to a horrible and sad footnote in human history.
| walrus01 wrote:
| 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.
| aredox wrote:
| Both nuclear weapons and ballistic missiles are technologies
| from the 1940's.
|
| They don't need outside help.
| laurencerowe wrote:
| 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...
| dontbenebby wrote:
| >Missiles make ionospheric disturbances that GPS records. The
| yellow ripple is the ionospheric disturbance.
|
| Where can I read more about the meta level concept of "isopheric
| disturbances"? (Because I suspect I'll find this has been done by
| military intelligence for a long time then rediscovered by so
| called "arms control" wonks who insist on putting their code into
| the public domain.)
| teeray wrote:
| 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.
| krisoft wrote:
| 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.
| dontbenebby wrote:
| >You say that as if there is something wrong with that.
|
| So to be clear, you an arms control expert public domaining
| code that aids totalitarians like Putin and the North Koreans
| has... "nothing wrong with that"?
|
| Some domain specific knowledge was meant to be esoteric* and
| there are a variety of better licenses such as CC-non-
| commercial that allow peaceful uses of the code without
| allowing it to be used by _literally_ anyone on the planet.
|
| (*Unless you pay the proper fees, of course. But that's not
| just about money... you have to earn the right to make the
| purchase.)
| Dylan16807 wrote:
| I do not feel bad about indirectly aiding them with well-
| after-the-fact missile trail detection. Why should I? Why
| should this be difficult to do?
|
| It can be called "military" but it doesn't help with
| offenses and doesn't really help with defenses either.
| dontbenebby wrote:
| >well-after-the-fact missile trail detection.
|
| Sorry, I missed that bit, I thought this could also be
| used to detect incoming missiles.
|
| I do not want my enemies to be able to detect incoming
| missiles.
|
| Sorry for posting so angrily.
| kadoban wrote:
| To do anything about incoming missiles, you'd need
| extremely low latency tracking, integrated into whatever
| system you're using anyway. Not sure exactly you'd be
| worried about even if this was near-real-time.
| rosnd wrote:
| You could probably use techniques like this to rig an
| early warning system on enemy territory, but there are of
| course better options.
| thot_experiment wrote:
| Wild! I don't think I've ever seen someone who thinks
| restricting tech like this is actually a good idea. I
| thought that was just like, crazy government people who
| don't understand technology.
|
| I'd hoped we'd moved past printing the entire code of PGP
| in a hardback book in an OCR font but I guess y'all still
| out here.
| InCityDreams wrote:
| " /s", spotted on my end.
| Xylakant wrote:
| 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.
| EmilioMartinez wrote:
| What does "gravity waves" mean in this context?
| ilyt wrote:
| That's one of most impressive examples of essentially "passive
| radar" I"ve seen!
| darepublic wrote:
| After-effects of WW2 still posing existential threat to us all..
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