In North Korea yesterday, there was a large, unexplained explosion, with an accompanying mushroom cloud. There have understandably been some worries that this was a nuclear test.
My understanding – and I ask the Teeming Millions for further enlightenment – is that there have been satellites operating since the 60’s that would detect well nigh any nuclear event via its gamma ray emissions.
I was curious enough to google for details, and here’s what I’ve googled:
The Vela series of satellites were deployed in the mid '60s to detect nuclear events via gamma signature.
Vela and IMEWS both appear offline, but I’m not finding what superceded them. What is the current system?
What is the current (and past if relevent) capability for detecting a nuclear event? Is gamma burst detection world wide, or dependant on satellite orbit?
Can a nuclear event be hidden either by coordinates (e.g. the south pole or some other difficult location for some satellites), or timing (satellite orbits) or other means?
Most importantly: could NK have conducted a nuclear test undetected?
Well, first off, it is incredibly unlikely that the explosion, if it was a nuclear device, was a hydrogen bomb. (I’m assuming that’s what you mean by h-explosion.) Secondly, the only good way to “hide” a test is underground. However, due to the treaty signed way-back-when that banned all above-ground testing (between signatories, of course), I’m sure that at least the US and Russia got very good at detecting such tests seismically.
Don’t know about gamma , but the DSP warning sats , can detect the heat bloom of a surface detonation.
Hard for me to say , as the current orbit of the DSP sats are somewhere in GeoSync range , to give world wide coverage , so I have no idea if there are gaps in coverage.
The south africans and the Israeli joint team, was able to detonate a nuke in the indian ocean , but that was sometime back in the seventies and current tech may render that approach defunct.
The Indians were able , recently to detonate an underground nuke , but that was due to inteligence means ,rather than technological, for surprise.
If the DSP sats did not register a surface detonation , then the seismic sensors would have, it supposedly makes a unique spike on the twitchy thing.
Gah, tripped by terminology. You’re quite right, “h-explosion” might imply a hydrogen bomb. But I think you might reasonably assume I meant “a fission driven explosive device” – e.g. hiroshima – right?
My admittedly quaint understanding is that the gamma sig is not hidden when underground, but please correct me on this. I’m not that familiar with seismic signatures – wouldn’t that require monitoring stations in fairly close proximity (e.g. a couple of hundred kms) from the event?
Umm, the current capabilities of that system are classified ,both in sensors and coverage. The system was designed to give early warning regarding a soviet inbound nuclear strike , and as such would probably cover the whole globe.
Using the example of the South pole as the site of the nuclear event , and this is a guess , the system would know because of the flash ,but the amount of detail it could provide , is as mentioned classified.
Other than general knowledge that it exists (dsp sats) and that it was able to track the launch plumes of the scud missiles in Desert Storm , thats about it for my knowledge of it.
Well, there is undetected and undetected.
I believe that the blast was detected , but it was sometime before the nationalitys were known
Declan
Please correct me if I’ve gathered the wrong impression, but DSP detectors are only useful for detecting missile launch events, not nuclear fission detonations. Correct?
Interesting: the pages for the DSP and GPS (very clever, putting the sensors on GPS Sats!) systems both emphasize that they can above ground nuclear events. DSP is apparently an IR-only system and can also detect missile launches. The GPS sats also detect x-rays, though it’s unclear to me why an x-ray detector can only detect above-ground tests.
Are gamma-ray detectors no longer used? Could NK or others conduct an underground nuclear test that might go undetected?
Way long ago, in the deeps of time, when many of today’s Dopers were not even conceived, I was an undergrad working in geophysics. We were gathering data on seismic events that crossed the Himalayas in order to study the makeup of the Himalayas – exactly how were India and Asia colliding? We gathered data from seismograms from all over the world, but particularly from Asia.
The upshot is, the work was being funded in part by the Navy. Why the hell would the Navy care about mountains? Because they wanted to be able to look at traces from seismic events and distinguish between earthquakes and underground nuclear tests.
That was some thirty years ago. I’m sure they’ve gotten even better at it. And “close” is a relative term – seismic events make waves (literally) all over the world.
Earth (dirt, rocks, etc.) are pretty good at shielding radiation. If you have your bomb burried deep enough that it won’t just blow the covering off, you’ve got easily far more than enough dirt and rocks to stop all of the X and gamma rays.
Meanwhile, you’ve got the question of why a country would want to keep a test secret. You probably already know ahead of time that the device is going to work: Your reason for testing it is to make it absolutely clear to the rest of the world that you’re now a nuclear power. Nukes do a country no good if nobody knows you have them.
Chronos brought up some great reasoning about why you would want to keep a test secret if you have nuclear weapons.
However, there may be reasons you want to keep the world guessing too. If you don’t have nuclear weapons, there may be reason to want the world to think you do (Iraq may have been trying to follow this sort of tactic with stalling and harassing the weapons inspectors, and a heck of a lot of good it did them :rolleyes: ). Perhaps many people already think you have nuclear weapons and you want them to continue to think that, even if you don’t, (if that’s the case with the current controversy, the absence of reports of radioactive fallout is a big problem for the North Koreans). Maybe you don’t have many nuclear weapons, but you want the world to think you have enough to expend on a testing program.
None of this makes a compelling arguement for the recent explosion as a nuclear test, but I just thought I’d add a couple other possibilities to the mix.
I agree. Let’s face it, until the partial test-ban treaty, atomic tests were as much sabre-rattling and intimidation as they were for actually testing the device. The only test that was worth keeping secret was Trinity.
So a nuclear explosion would have a clear seismic signature. Position of the blast could be triangulated from information obtained from scattered monitoring stations. It might still be possible to hide a small nuclear explosion by simultaneously detonating a large chemical one in close proximity.
