On 8/5/20 12:40 PM, Tom Knox wrote:
Hi Paul and Magnus;
Not to mention one space EMP would kill all the Sat systems, where a ground
base system even if affected would be easy to access for repair.
The vulnerability of GNSS systems to EMP attacks is not all that high -
GPS is, after all, a DoD essential system, and lives in a ridiculously
high radiation environment in MEO - They're also hard to neutrons (based
on published specs for components in the GNSS satellites).
In most scenarios, LEO satellites get hammered, MEO and GEO not so much.
https://apps.dtic.mil/dtic/tr/fulltext/u2/a531197.pdf
"GPS and GEO satellites are threatened only by the very high yield (~ 10
Mt) detonations of our trial set."
I'll note that the largest the US has detonated in space are the Teak
and Orange shots 3.8Mt (at <100km), and only Starfish Prime (1.4Mt) at
400km cased significant problems.
The usual "use case" for EMP is to affect aircraft and ground based
assets, and the burst height is low (so the air around the burst is
denser - more particle interactions = more current = more field) -
conversely, this reduces the flux at 20,000 km (where GPS is) and
36,000km (GEO)
Ultimately, it's that your victim is a Long, long ways away from
whatever the phenomenon is.
I've been doing a lot of analysis on EMI/RFI effects on precision timing
in GEO+1000km - we are looking at bursts from the sun, and timing it
with GNSS satellites. Things that I agonized over (high power shortwave
broadcasters radiating 500kW into a 24dBi curtain array) in my LEO
satellite at 500km just become a non-issue at 37,000 km. Inverse square
law really helps.
Anyway, that DTIC report will give you plenty to geek out over.
Yes, there would be significant disruption in timing accuracy due to the
ionized particles - I'm not sure if dual frequency would be enough to
compensate.
I think alternate timing and nav systems are good idea, but selling it
as "GPS will be knocked out by EMP" isn't going to get you very far.
Cheers;
Tom Knox
[email protected]
"Peace is not the absence of violence, but the presence of Justice" Both MLK
and Albert Einstein
________________________________
From: time-nuts <[email protected]> on behalf of paul swed
<[email protected]>
Sent: Wednesday, August 5, 2020 11:21 AM
To: Discussion of precise time and frequency measurement
<[email protected]>
Subject: Re: [time-nuts] eLORAN will be on the air GRI 99600
Hi Magnus been a while since have emailed.
Its one site that was a test transmitter. Its in New Jersey, USA.
The goal of the testing I believe is to establish the viability of an
alternate PNT reference to GPS. Additionally the ability to communicate
some level of message broadcast. This should be identical to proposals I
have heard of in Europe.
But I have no direct relationship to any of this. Like you, a very
interested observer and hope that eLORAN wins the battle.
Unfortunately there are many alternate proposals such as using other
satellites. Hmmm if I wanted to advance my career in the Air Force or Space
Force (Yes thats actually real now).
Would I select the lowly reliable as heck eLORAN at sub $100 M/year to
operate. Or the glorious space based proposals in $B region. Never mind
that at least 3 countries now have demonstrated killer satellites.
Sorry for that editorial.
Regards
Paul
WB8TSL
On Wed, Aug 5, 2020 at 11:04 AM Magnus Danielson <[email protected]> wrote:
Hi,
Do you know that they would do test with two actual transmitter sites?
Cheers,
Magnus
On 2020-08-05 16:00, paul swed wrote:
Hello to fellow time nuts.
Warm up those old Austrons. eLORAN out of New Jersey has been on the air
intermittently prior to a test run next week. Due to the storm they have
lost power and should have it back today or tomorrow.
The intention will be on the air operation till the 20th. That's a long
run. Nice.
Seems the Austron 2100s can be had for reasonable money these days also.
Enjoy.
Paul
WB8TSL
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