Author Topic: Galileo constellation down for four days  (Read 2365 times)

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Offline tooki

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Re: Galileo constellation down for four days
« Reply #25 on: November 12, 2019, 09:57:36 pm »

Plenty of military tech depends on GPS so quite the opposite is true :)
But, there are TWO GPS systems, one commercial, one military.  The decryption keys to the military one are not published.
They can turn off the commercial one (or dilute the precision) without affecting the military system.  And, diluted precision is not an on/off setting, they can dilute it to any amount they want.

Jon
Nope. You are simply describing (not fully correctly) the Selective Availability feature that has been disabled since 2000 and cannot be re-enabled because the newer GPS satellites do not support it.

There is not, and never has been, a separate military GPS. It was born as a military project, with civilian use as an afterthought. They used encryption to encode the error into the signal, which a military receiver with the daily key could decrypt to full resolution, while civilian receivers had the error. But the error has been set to zero since 2000, and as I said, can’t be enabled any more.

According to the government, military GPS receivers are dual-band, while civilian ones are largely single-band, but for cost reasons only. They expressly say that dual-band civilian receivers do exist. See https://www.gps.gov/systems/gps/performance/accuracy/#difference
 
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Offline tooki

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Re: Galileo constellation down for four days
« Reply #26 on: November 12, 2019, 10:01:17 pm »
All systems have separate channels for public and military use, as well as SA capability (of the public channel), as well as the channels can be switched off/on anytime. I can hardly imagine how you would limit its usage in certain areas like a "border of a state".
The SA does not work such the public service will not be available to a certain state or entity, but it dithers the signal such the precision goes down from say ~10m to ~100m. That is all. US had switched SA on many times on the public channel in past and nobody from public sector noticed that, afaik.
The military channels are not subject of the SA, of course (as you cannot decrypt them with cheapo devices we all use).
SA is there to avoid the situation Dr.No would put his $20 phone with GPS into a rocket he will shoot and navigate against James Bond's yacht.
Nope nope nope.

1. There’s no separate military GPS, and never has been. Edit: see forrestc’s comment below.
2. SA was always turned on before 2000, except in the Gulf War, when there were not enough military GPS receivers, so the military let them use civilian receivers and disabled SA in the gulf region. Since 2000, SA has been turned off and now cannot be reenabled.
3. When SA was used, military receivers used the daily key to decrypt the error correction to compensate for the intentional error. They did not have a separate signal.
« Last Edit: November 13, 2019, 10:13:45 am by tooki »
 
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Offline Someone

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Re: Galileo constellation down for four days
« Reply #27 on: November 12, 2019, 10:26:53 pm »
All systems have separate channels for public and military use, as well as SA capability (of the public channel), as well as the channels can be switched off/on anytime. I can hardly imagine how you would limit its usage in certain areas like a "border of a state".
The SA does not work such the public service will not be available to a certain state or entity, but it dithers the signal such the precision goes down from say ~10m to ~100m. That is all. US had switched SA on many times on the public channel in past and nobody from public sector noticed that, afaik.
The military channels are not subject of the SA, of course (as you cannot decrypt them with cheapo devices we all use).
SA is there to avoid the situation Dr.No would put his $20 phone with GPS into a rocket he will shoot and navigate against James Bond's yacht.
Political weasel words as usual, promises to never enable SA (lock the door to the public), but no mention they won't just jam all civilian use (put barriers/dogs in front of the door). Acknowledgement that jamming does happen:
https://www.easa.europa.eu/easa-and-you/air-operations/czibs/czib-2017-03r5
No specifics of who may be doing that jamming....


Plenty of military tech depends on GPS so quite the opposite is true :)
But, there are TWO GPS systems, one commercial, one military.  The decryption keys to the military one are not published.
They can turn off the commercial one (or dilute the precision) without affecting the military system.  And, diluted precision is not an on/off setting, they can dilute it to any amount they want.

Jon
Nope. You are simply describing (not fully correctly) the Selective Availability feature that has been disabled since 2000 and cannot be re-enabled because the newer GPS satellites do not support it.

There is not, and never has been, a separate military GPS. It was born as a military project, with civilian use as an afterthought. They used encryption to encode the error into the signal, which a military receiver with the daily key could decrypt to full resolution, while civilian receivers had the error. But the error has been set to zero since 2000, and as I said, can’t be enabled any more.

According to the government, military GPS receivers are dual-band, while civilian ones are largely single-band, but for cost reasons only. They expressly say that dual-band civilian receivers do exist. See https://www.gps.gov/systems/gps/performance/accuracy/#difference
Non-millitary GPS receivers may "use" the additional frequency signal, but they are not decoding the additional information within the M coding:
https://en.wikipedia.org/wiki/GPS_signals#Military_(M-code)
Unsurprisingly there isn't much detail publicly available on what additional payloads and signal characteristics are available for military use.
 

Offline Sal Ammoniac

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Re: Galileo constellation down for four days
« Reply #28 on: November 12, 2019, 11:33:49 pm »
Political weasel words as usual, promises to never enable SA (lock the door to the public), but no mention they won't just jam all civilian use (put barriers/dogs in front of the door).

You have to remember that GPS is a military system and any subsequent non-military use has been a side-effect, not a planned use. Complaining about the military disabling civilian use would be like watching your neighbor's TV through his living room window and then complaining when he closes the curtains.
Nothing lasts as long as a workaround.
 
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Offline 0culus

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Re: Galileo constellation down for four days
« Reply #29 on: November 12, 2019, 11:49:48 pm »
Another key difference between what's available to the non military market vs the military: civilian GPS receivers will disable themselves if they detect they are above a certain altitude traveling above a certain speed...this is to ensure you can't use a cell phone GPS to guide your makeshift ICBM.
 

Offline CatalinaWOW

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Re: Galileo constellation down for four days
« Reply #30 on: November 13, 2019, 03:39:08 am »
Another key difference between what's available to the non military market vs the military: civilian GPS receivers will disable themselves if they detect they are above a certain altitude traveling above a certain speed...this is to ensure you can't use a cell phone GPS to guide your makeshift ICBM.

While I endorse this as a sensible thing to do, is there any law or enforcement?  Is it true of all sensors?  I know that many commercial GPS sensors stop working at relatively low altitudes and speeds to similarly limit their use in airline terrorism, but clearly there are commercial GPS that work under those conditions in the cockpits of the airliners and in many GA aircraft.
 

Offline BravoV

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Re: Galileo constellation down for four days
« Reply #31 on: November 13, 2019, 04:12:41 am »
Another key difference between what's available to the non military market vs the military: civilian GPS receivers will disable themselves if they detect they are above a certain altitude traveling above a certain speed...this is to ensure you can't use a cell phone GPS to guide your makeshift ICBM.

While I endorse this as a sensible thing to do, is there any law or enforcement?  Is it true of all sensors?  I know that many commercial GPS sensors stop working at relatively low altitudes and speeds to similarly limit their use in airline terrorism, but clearly there are commercial GPS that work under those conditions in the cockpits of the airliners and in many GA aircraft.

Personally, I've experienced my self, using my smartphone with GPS app, in offline (air-plane) mode of course, sitting at window seat, from my memory, average the plane's top speed was about 800 km/h (500 mph) at top altitude about 10 km (32.000 feet), I guess this range is still allowed for civilian's GPS ?  :-//

Also fyi, Google map works too to see the plane location which is pretty cool as its live, with offline map loaded before hand at the flight route, as I love to use it whenever I had long flight and seated at window seat.

Offline Red Squirrel

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Re: Galileo constellation down for four days
« Reply #32 on: November 13, 2019, 05:19:20 am »
Have they tried doing a full hard reset by holding the power button for 5 seconds and then turning it back on?   :P  Maybe eventually they will have a Geek Squad space division with little SSTO service vans. 
 

Offline Halcyon

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Re: Galileo constellation down for four days
« Reply #33 on: November 13, 2019, 05:43:55 am »
in offline (air-plane) mode of course

Why "of course"? Many airlines offer in-flight entertainment applications (essentially BYO device for watching movies via their Wi-Fi network) and some flights even offer internet connectivity (probably at exorbitant prices). The only reason for switching your phone off is so that they don't pose a distraction during the safety brief or so you don't annoy other passengers. Qantas (Australia's largest carrier) offers free Wi-Fi internet on selected aircraft.

Most pilots on both private and commercial flights actively use their mobile phones and tablets during flight (obviously cellular coverage will vary significantly with altitude).

The old myth that mobile phones will cause disruption to aircraft systems needs to die, along with using a mobile phone next to a petrol pump will cause a fire/explosion.
 
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Offline BravoV

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Re: Galileo constellation down for four days
« Reply #34 on: November 13, 2019, 05:46:28 am »
in offline (air-plane) mode of course

Why "of course"? ....

....The only reason for switching your phone off is so that they don't pose a distraction during the safety brief or so you don't annoy other passengers.

Yep, there, you've answered it yourself, cheers.  ;)
 
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Offline Halcyon

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Re: Galileo constellation down for four days
« Reply #35 on: November 13, 2019, 05:49:50 am »
in offline (air-plane) mode of course

Why "of course"? ....

....The only reason for switching your phone off is so that they don't pose a distraction during the safety brief or so you don't annoy other passengers.

Yep, there, you've answered it yourself, cheers.  ;)

Each to their own I suppose. I just put my phone on silent while flying. I still like to receive email and SMS messages during flights.
 

Offline 0culus

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Re: Galileo constellation down for four days
« Reply #36 on: November 13, 2019, 06:01:45 am »
Another key difference between what's available to the non military market vs the military: civilian GPS receivers will disable themselves if they detect they are above a certain altitude traveling above a certain speed...this is to ensure you can't use a cell phone GPS to guide your makeshift ICBM.

While I endorse this as a sensible thing to do, is there any law or enforcement?  Is it true of all sensors?  I know that many commercial GPS sensors stop working at relatively low altitudes and speeds to similarly limit their use in airline terrorism, but clearly there are commercial GPS that work under those conditions in the cockpits of the airliners and in many GA aircraft.

Personally, I've experienced my self, using my smartphone with GPS app, in offline (air-plane) mode of course, sitting at window seat, from my memory, average the plane's top speed was about 800 km/h (500 mph) at top altitude about 10 km (32.000 feet), I guess this range is still allowed for civilian's GPS ?  :-//

Also fyi, Google map works too to see the plane location which is pretty cool as its live, with offline map loaded before hand at the flight route, as I love to use it whenever I had long flight and seated at window seat.

Commercial flights are *much* lower and slower than a ballistic missile though. Look up the phrase "COCOM Limits". The tl;dr is that GPS receivers that aren't listed in the US ITAR cannot function at speeds over 1000 knots over the ground or altitudes over 60,000 feet. You can probably find receivers that don't have these limits, but they will not be exportable.

Of course, given the technical expertise, it should be possible to roll your own. You might end up on some kind of list though.  :-DD
 
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Offline BravoV

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Re: Galileo constellation down for four days
« Reply #37 on: November 13, 2019, 06:06:37 am »
Commercial flights are *much* lower and slower than a ballistic missile though. Look up the phrase "COCOM Limits". The tl;dr is that GPS receivers that aren't listed in the US ITAR cannot function at speeds over 1000 knots over the ground or altitudes over 60,000 feet. You can probably find receivers that don't have these limits, but they will not be exportable.

Of course, given the technical expertise, it should be possible to roll your own. You might end up on some kind of list though.  :-DD

LOL .. yeah, no doubt bout that, prolly in those 3 characters gov agencies.  :-DD

Offline forrestc

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Re: Galileo constellation down for four days
« Reply #38 on: November 13, 2019, 06:42:56 am »
1. There’s no separate military GPS, and never has been.
2. SA was always turned on before 2000, except in the Gulf War, when there were not enough military GPS receivers, so the military let them use civilian receivers and disabled SA in the gulf region. Since 2000, SA has been turned off and now cannot be reenabled.
3. When SA was used, military receivers used the daily key to decrypt the error correction to compensate for the intentional error. They did not have a separate signal.

This isn't 100% accurate.   There are very definitely portions of the GPS signal which are not available to civilian users, even today.  Before modernization, the civilian C/A code was transmitted only on the L1 carrier.   The military-only P(Y)-code was transmitted on both the L1 and L2 carriers.    Recently the military has been adding additional civilian signals on the L2 and also L5 band.   See https://www.gps.gov/systems/gps/modernization/civilsignals/ and https://gssc.esa.int/navipedia/index.php/GPS_Performances (US Government, ESA)

So, I agree that there aren't two separate GPS systems, but the GPS satellites do provide military-only positioning services.

A random note:   The military signal on the L2 carriers have been used for some civilian uses, usually related to time transfer.  However, these techniques typically don't rely on decoding the signal, only looking at the relative phase of the signal being received from the satellites.


« Last Edit: November 13, 2019, 06:45:46 am by forrestc »
 
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Offline tooki

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Re: Galileo constellation down for four days
« Reply #39 on: November 13, 2019, 10:11:15 am »
Thank you for the clarification!

It seems to me that no matter what, the US military isn’t going to ever degrade civilian GPS, which is the big concern. (Its use in aviation is why the FAA pressured them into permanently disabling SA.) I don’t care if they add on extra features for military use, since that doesn’t take away from civilian use.
 

Offline BravoV

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Re: Galileo constellation down for four days
« Reply #40 on: November 13, 2019, 10:13:02 am »
A random note:   The military signal on the L2 carriers have been used for some civilian uses, usually related to time transfer.  However, these techniques typically don't rely on decoding the signal, only looking at the relative phase of the signal being received from the satellites.

Is it used by GPSDO ? Or not norm ?

Offline soldar

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Re: Galileo constellation down for four days
« Reply #41 on: November 13, 2019, 10:50:54 am »
Another key difference between what's available to the non military market vs the military: civilian GPS receivers will disable themselves if they detect they are above a certain altitude traveling above a certain speed...this is to ensure you can't use a cell phone GPS to guide your makeshift ICBM.

I believe this is not correct. I believe there is no government mandate to disable a receiver above a certain speed or altitude. I believe GPS receiver manufacturers will certify certain receivers for flight navigation and they prefer to sell those to a pilot than to have him using a non-certified receiver. That is all. Just like electronic components for use in medical devices, airplanes, military, satellites, need to be especially certified.  Many years ago, when GPS receivers were much more expensive, I talked to a guy who flew a small airplane and he told me he used a commercial receiver that did not work at speed but he could slow down enough to get a fix and then continue on his way.


An interesting thing is that the use of GPS receivers is illegal in China because they consider maps to be of national security importance and all official maps are distorted. The whole thing is demented in an age where you can go to Google Earth and find anything you want. I have always taken my Garmin receiver to China and never had a problem but it is technically illegal. Also my phones' GPS worked fine in China but, again, technically illegal. Photo cameras sold in China automatically disable the GPS locator if they detect they are inside China and many manufacturers just sell all their cameras worldwide with that. I once ran into a German guy in China who told me GPS was blocked in China and I told him my GPS was working fine. At the time I did not know his camera, bought in Germany, disabled the GPS when in China.
« Last Edit: November 13, 2019, 10:54:31 am by soldar »
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Offline imo

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Re: Galileo constellation down for four days
« Reply #42 on: November 13, 2019, 11:33:18 am »
There are restrictions, and are implemented in almost all civilian GPS modules, afaik.
For example ublox says above 50km altitude the precision is not guaranteed, and above 500m/s the module will not output data altitude regardless..

https://portal.u-blox.com/s/question/0D52p00008HKChmCAH/clarifying-the-velocity-limit-of-500-msec

The limits (also stated in the datasheets) vary somehow based which documents you are reading. I've seen altitudes like 18km, 30000feet, 60000feet, 50km, velocities 1000knots, 500m/s, 600m/s..
« Last Edit: November 13, 2019, 11:51:46 am by imo »
 

Offline forrestc

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Re: Galileo constellation down for four days
« Reply #43 on: November 13, 2019, 12:01:32 pm »
A random note:   The military signal on the L2 carriers have been used for some civilian uses, usually related to time transfer.  However, these techniques typically don't rely on decoding the signal, only looking at the relative phase of the signal being received from the satellites.

Is it used by GPSDO ? Or not norm ?

No, not normally.   The specific application I'm aware of is for very precise time transfer, far beyond what you would normally encounter.   Think NIST or other very high precision time and frequency transfer, typically at a country standards organization level.   Think: synchronize atomic clocks, not the normal ovenized crystal oscillators in a GPSDO.

I'm guessing there are other applications I'm not specifically aware of.  If you're interested, search for "codeless GPS". 
 
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Offline forrestc

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Re: Galileo constellation down for four days
« Reply #44 on: November 13, 2019, 12:23:38 pm »
I believe this is not correct. I believe there is no government mandate to disable a receiver above a certain speed or altitude. I believe GPS receiver manufacturers will certify certain receivers for flight navigation and they prefer to sell those to a pilot than to have him using a non-certified receiver.

Actually, it's more complicated than that.

GNSS receivers with certain capabilities are classified as Munitions by various countries and as a result are subject to Export Controls.   So if you include a GPS receiver in your product which has capabilities beyond these limits then you end up needing an export license to be able to export that product.   In the US, until a few years ago this included an altitude and speed threshold of 60,000 ft and 1000 knots.   These were called the "COCOM" limits which was basically the name of the regulation that led to these limits.

I am not sure if there are any remaining rules globally as to speed and altitude.  I know that in the US there are still certain limits such as "GNSS receiving equipment specially designed for use with rockets, missiles, SLVs, drones, or unmanned air vehicle systems capable of delivering at least a 500 kg payload to a range of at least 300 km" but there don't seem to be hard limits anymore.  But since much of the software has these limits coded in them, then it's sort of stuck around.

 

Offline soldar

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Re: Galileo constellation down for four days
« Reply #45 on: November 13, 2019, 06:08:27 pm »
Actually, it's more complicated than that.

Everything is more complicated than we think and even than we can imagine. :)
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Online GlennSprigg

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Re: Galileo constellation down for four days
« Reply #46 on: November 18, 2019, 11:36:14 am »
'Flat Earthers' would love hearing/thinking that a fake actual 'Constellation' went down!!!   :palm:
 
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