Re: [time-nuts] GPS PRN 32

[Martin Burnicki]

Magnus Danielson wrote:
> Charles,
> 
> Considering how the UTC parameters (IS-GPS-200H, Table 20-IX and section
> 20.3.3.5.2.4) got upset for some of the SVNs, the correction from GPS
> time (as corrected for that PRN) into UTC got a shift of almost 13,7 us.
> As a GPS receiver receives information, solves for position and time
> (fixed timing receivers naturally only for time), correct into GPS time
> and then into UTC you end up with having to select the information from
> one of the GPS satellites for translating the GPS time into UTC time.
> Depending on the state of that GPS receiver, it may or may not select
> this bad info, and it may change selection at any time. That's why we
> have observed receivers of the same brand and same FW fail at different
> times, but starting having problems at the same trigger time. While
> there can be receivers that have some form of protection from this
> particular problem, I guess many don't, and in this case, the specifics
> of the receiver FW and the actual state of the receiver may have cause
> the full range of heavy to no impact. I would be careful to make to much
> judgment of various receivers because of this. It is clear that it's a
> serous hit to at least most of them.

Absolute correct, IMO.

> I remember the impacts from PRN 31 and PRN 32. The re-occuring GPS WN
> wrapping issue is another. This instance is rather unique in it being
> related to the ground infrastructure seems to have provided bad upload.
> 
> There is an intense amount of work behind the scenes. Some patience will
> be needed before even a minimalistic statement can be found.

Now there's a statement available. See my other post.

Martin

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Re: [time-nuts] GPS PRN 32

[Magnus Danielson]

Charles,

Considering how the UTC parameters (IS-GPS-200H, Table 20-IX and section 
20.3.3.5.2.4) got upset for some of the SVNs, the correction from GPS 
time (as corrected for that PRN) into UTC got a shift of almost 13,7 us. 
As a GPS receiver receives information, solves for position and time 
(fixed timing receivers naturally only for time), correct into GPS time 
and then into UTC you end up with having to select the information from 
one of the GPS satellites for translating the GPS time into UTC time. 
Depending on the state of that GPS receiver, it may or may not select 
this bad info, and it may change selection at any time. That's why we 
have observed receivers of the same brand and same FW fail at different 
times, but starting having problems at the same trigger time. While 
there can be receivers that have some form of protection from this 
particular problem, I guess many don't, and in this case, the specifics 
of the receiver FW and the actual state of the receiver may have cause 
the full range of heavy to no impact. I would be careful to make to much 
judgment of various receivers because of this. It is clear that it's a 
serous hit to at least most of them.


I remember the impacts from PRN 31 and PRN 32. The re-occuring GPS WN 
wrapping issue is another. This instance is rather unique in it being 
related to the ground infrastructure seems to have provided bad upload.


There is an intense amount of work behind the scenes. Some patience will 
be needed before even a minimalistic statement can be found.


Cheers,
Magnus

On 01/27/2016 09:38 AM, Charles Curry wrote:

Update on PRN 32 / SVN 23

According to the NANU this was decommissioned at 22:00 on the 25th. It was 25 
years old http://archive.is/a8GI

Some timing receivers experienced problems, some did not. Don't know why that 
is yet.

So far our count is 8 different GPS timing receivers experiencing problems - 
ranging from mid '90's models, but still in service to the latest new devices. 
Problems included loss of lock, squelching of outputs, pulling the frequency 
off and massive pps jumps. In one case the output of a receiver was so bad it 
was rejected by the equipment it was feeding but the receiver did not alarm!

A couple of units in my lab, based on the latest multi-constellation engine 
from a major supplier, one with Rb one with CSAC, exhibited 5 or 6 phase jump 
events from about 1:45 am until 12:30pm on the 26th. Our support team was kept 
busy from about 2 am on the 26th with at least 7 of our timing equipment 
customers reporting GPS errors.

It looks like bad ephemeris was being broadcast from some satellites.

I would say this is a similar problem to the April 1st 2014 Glonass outage 
reported here http://gpsworld.com/the-system-glonass-in-april-what-went-wrong/

Charles
charles.cu...@chronos.co.uk




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Re: [time-nuts] GPS PRN 32

[Charles Curry]

Tom

This is what I sent unchecked Rich Text (HTML) now

Has anyone noticed GPS problems today?

It looks like PRN32 / SVN 23 went faulty yesterday and was taken out of service 
last night at 22:00 ZULU

http://www.navcen.uscg.gov/?Do=gpsShowNanu=2016008

We've seen issues with a number of timing receivers so far.

Best Regards,

Charles
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--- Original Message ---

From: "Tom Van Baak" 
To: "Charles Curry" 
Cc: "John Ackerman" 
Date: Tue, 26 Jan 2016 08:11:21 -0800
Subject: Re: GPS PRN 32

Hi Charles,

Your posting just now is completely blank (see below).
Was this an accident? Or perhaps your email client is configured for HTML-only 
instead of TEXT or TEXT+HTML.
Let me know if I can help.

Thanks,
/tvb

- Original Message -
From: "Charles Curry" 
To: "John Ackerman" 
Sent: Tuesday, January 26, 2016 7:26 AM
Subject: GPS PRN 32


>

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Re: [time-nuts] GPS PRN 32

[Magnus Danielson]

Hi,

It seems that several SVNs (PRN 2, 6, 7, 9 and 23) got feed bad data. 
This is not the first instance, it seems that single SVNs have had bad 
data the last couple of days.


When our 4 GPS receivers at work got "hit" at midnight, it got our 
attention. Interestingly enough they did not experience issues at the 
same time, it just started about the same time.


Several of my customers also reported issues. Turns out that more people 
seen this.


It will be interesting when a proper analysis comes on this.

Cheers,
Magnus

On 01/26/2016 05:43 PM, Charles Curry wrote:

Tom

This is what I sent unchecked Rich Text (HTML) now

Has anyone noticed GPS problems today?

It looks like PRN32 / SVN 23 went faulty yesterday and was taken out of service 
last night at 22:00 ZULU

http://www.navcen.uscg.gov/?Do=gpsShowNanu=2016008

We've seen issues with a number of timing receivers so far.

Best Regards,

Charles
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Managing Director
Chronos Technology Ltd


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Switchboard: +44 (0)1594 862 200
Direct: +44 (0)1594 862 201
Mobile: +44 (0)7786 336 001

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www.gps-world.biz
www.taviga.co.uk


Skype Laptop: chascurry


This email has been sent to you by Chronos Technology Limited; Registered in 
England and Wales Number: 2056049; VAT Number: GB 791312044; Registered Office: 
Stowfield House, Upper Stowfield, Lydbrook, Gloucestershire, GL17 9PD.
All data and information contained in this e-mail is in confidence and is the 
copyright of Chronos Technology Limited and/or its Suppliers. No information 
contained in this e-mail may be released, republished or incorporated into any 
other work without the prior written consent of the discloser and/or copyright 
owner.

--- Original Message ---

From: "Tom Van Baak" 
To: "Charles Curry" 
Cc: "John Ackerman" 
Date: Tue, 26 Jan 2016 08:11:21 -0800
Subject: Re: GPS PRN 32

Hi Charles,

Your posting just now is completely blank (see below).
Was this an accident? Or perhaps your email client is configured for HTML-only 
instead of TEXT or TEXT+HTML.
Let me know if I can help.

Thanks,
/tvb

- Original Message -
From: "Charles Curry" 
To: "John Ackerman" 
Sent: Tuesday, January 26, 2016 7:26 AM
Subject: GPS PRN 32






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Re: [time-nuts] GPS PRN 32

[Charles Steinmetz]

Magnus wrote:

Interestingly enough they did not experience issues at the same 
time, it just started about the same time.


Presumably, each rx would be affected when it added one or more 
corrupted satellites to the constellation it was using for its 
solution.  Since each rx makes those decisions independently, one 
would not expect them to exhibit problems in exact synchrony.


Best regards,

Charles


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Re: [time-nuts] GPS PRN 32

[Mike S]

One more comment on this, SV 32/PRN 32 was briefly in use in 1992-3.

SV-32 has been active since Dec 11. [1992] - 
http://igscb.jpl.nasa.gov/mail/igsreport/1992/msg00054.html

On 28 January (day 028) [1993],  SV-32's PRN number has been changed 
from PRN#32 to PRN#01 sometimes between UTC 20:55  and  UTC 21:20. - 
http://igscb.jpl.nasa.gov/mail/igsmail/1993/msg00095.html

According to the document 
http://www.thsoa.org/pdf/fugrognsshydrosociety2007.pdf , the use of PRN 
32, Caused problems with DOD applications not supporting  31 PRNs


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Re: [time-nuts] GPS PRN 32

[Tom Van Baak]

 One more comment on this, SV 32/PRN 32 was briefly in use in 1992-3.
 
 SV-32 has been active since Dec 11. [1992] - 
 http://igscb.jpl.nasa.gov/mail/igsreport/1992/msg00054.html
 
 On 28 January (day 028) [1993],  SV-32's PRN number has been changed 
 from PRN#32 to PRN#01 sometimes between UTC 20:55  and  UTC 21:20. - 
 http://igscb.jpl.nasa.gov/mail/igsmail/1993/msg00095.html
 
 According to the document 
 http://www.thsoa.org/pdf/fugrognsshydrosociety2007.pdf , the use of PRN 
 32, Caused problems with DOD applications not supporting  31 PRNs

Mike,

Yes, I heard this too. I don't know much about DoD receivers, though.
My guess is they don't show up on eBay for us bottom-feeder types.

BTW, NASA just fixed Jtrack3D for me so you can now select GPS
BIIA-10 (PRN32) from the list of valid satellites.

http://science.nasa.gov/Realtime/jtrack/3d/JTrack3D.html

I also put a cute pair of animated GPS PRN32 orbit tracks at:

http://www.leapsecond.com/pages/prn32/

Don't look at the first one too long; it will make you dizzy.

/tvb



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Re: [time-nuts] GPS PRN 32

[Magnus Danielson]

From: [EMAIL PROTECTED] (Mike S)
Subject: Re: [time-nuts] GPS PRN 32
Date: Sat, 09 Feb 2008 21:52:59 -0500
Message-ID: [EMAIL PROTECTED]

 At 07:42 PM 2/9/2008, Bruce Griffiths wrote...
 The Jupiter documentation indicates that PRN range is 1-32 with 0 used
 to indicate all satellites.
 
 You should be good, then, since the developers obviously accommodated a 
 PRN 32.
 
 The statement quoted from the original article (GPS receivers 
 initially were built to accommodate up to 31 satellite signals...) is 
 incorrect. The PRN range for space vehicles has always been 1-32. (see 
 Table 3-I in 
 http://www.navcen.uscg.gov/pubs/gps/icd200/ICD200Cw1234.pdf ). The 
 concern is that the code in some GPS receivers was poorly written, and 
 set up data structures to support PRNs 0-31, even though PRN 0 is, and 
 has always been, undefined.
 
 So problems are not a matter of the age of the receiver, but the 
 quality of its programming.

On the 13 December 2006 one operator saw their complete network fail as a
result, which was correlated to the enlargement of the GPS constellation.
The GPS receiver in question was an old 6 channel one. There is nothing wrong
with 6 channels receivers, as long as their firmware propperly handles all
sats. This particular receiver did not do it. Trouble is, their full network
was the same receiver and viewing the GPS receiver as a risk did not seem to
have been on their radar. They had the rugg pull away under their feets.

Hopefully no major failure will result from enabling PRN32. But we can't be
sure. It's not like we are testing all our receivers in GPS simulators for
these kind of situations

Cheers,
Magnus

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Re: [time-nuts] GPS PRN 32

[Chris Kuethe]

On Feb 8, 2008 2:07 PM, Bruce Griffiths [EMAIL PROTECTED] wrote:
 My Z3815A sees PRN 32 now albeit as unhealthy.

My Ublox AEK-4T has an almanac for PRN32, but no ephemeris (duh.)

haven't tried my AC12, Lassen iQ, itrax03, gps18/lvc, UT+, GT+ or Jupiter yet...

CK

-- 
GDB has a 'break' feature; why doesn't it have 'fix' too?

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Re: [time-nuts] GPS PRN 32

[Bruce Griffiths]

Chris Kuethe wrote:
 On Feb 8, 2008 2:07 PM, Bruce Griffiths [EMAIL PROTECTED] wrote:
   
 My Z3815A sees PRN 32 now albeit as unhealthy.
 

 My Ublox AEK-4T has an almanac for PRN32, but no ephemeris (duh.)

 haven't tried my AC12, Lassen iQ, itrax03, gps18/lvc, UT+, GT+ or Jupiter 
 yet...

 CK

   
Chris

The Jupiter documentation indicates that PRN range is 1-32 with 0 used
to indicate all satellites.
So you may have some luck with that receiver.

Bruce

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Re: [time-nuts] GPS PRN 32

[Tom Van Baak]

 The Jupiter documentation indicates that PRN range is 1-32 with 0 used
 to indicate all satellites.
 So you may have some luck with that receiver.
 
 Bruce

Bruce,

An actual test is in order, of course, but speaking as a software
engineer, anytime you hear 0 indicates all and 1 to 32 it's a
pretty good indicator that a 1-origin, 32-bit, fixed-length array is
being used.

I'll dig out my Res-t and give it a try.too. Thanks for the suggestion.

/tvb


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Re: [time-nuts] GPS PRN 32

[Bruce Griffiths]

The Novatel Superstar GPS receiver should also be OK for receiving PRN32.
The supplied software has provision for monitoring the health of all 32
possible satellites.
It also has provision for selectively ignoring any of the 32 possible
satellites.

Bruce

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Re: [time-nuts] GPS PRN 32

[Mike S]

At 07:42 PM 2/9/2008, Bruce Griffiths wrote...
The Jupiter documentation indicates that PRN range is 1-32 with 0 used
to indicate all satellites.

You should be good, then, since the developers obviously accommodated a 
PRN 32.

The statement quoted from the original article (GPS receivers 
initially were built to accommodate up to 31 satellite signals...) is 
incorrect. The PRN range for space vehicles has always been 1-32. (see 
Table 3-I in 
http://www.navcen.uscg.gov/pubs/gps/icd200/ICD200Cw1234.pdf ). The 
concern is that the code in some GPS receivers was poorly written, and 
set up data structures to support PRNs 0-31, even though PRN 0 is, and 
has always been, undefined.

So problems are not a matter of the age of the receiver, but the 
quality of its programming.



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Re: [time-nuts] GPS PRN 32

[Bruce Griffiths]

Tom Van Baak wrote:
 Which time-nut will be the first to see PRN 32 on Feb 19?
 I wonder what old GPS receivers won't be able to see it?

 This is from GPS World via NavtechGPS News...
 

 The U.S. military announced earlier this week that GPS satellite SVN23,
 transmitting L-band code as PRN32, will be set to usable status on
 Feb. 19. This is notable for a couple of reasons, but namely because
 it is the first time that the PRN32 designation will be used by an
 operational, healthy GPS satellite. 

 GPS receivers initially were built to accommodate up to 31 satellite
 signals, and a PRN designated with the number 32 can't be tracked by
 some manufacturers' devices that look for PRNs numbered 0 through 31.
 The U.S. Air Force began testing the PRN32 designation late in 2006 -
 while SVN23/PRN32 was set to unhealthy and not included in the
 operational GPS constellation almanac, some all-in-view GNSS tracking
 stations received the L-band signal.

 http://sidt.gpsworld.com/gpssidt/content/printContentPopup.jsp?id=490027

 

 /tvb

   
Tom

My Z3815A sees PRN 32 now albeit as unhealthy.

Bruce

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Re: [time-nuts] GPS PRN 32

[Poul-Henning Kamp]

In message [EMAIL PROTECTED], Bruce Griffiths writes:
Bruce Griffiths wrote:
 Tom

 My Z3815A sees PRN 32 now albeit as unhealthy.

 Bruce

   
My M12+ T doesn't see SVN 23 (PRN32) although its shares the same antenna.

By default the M12 will not track an unhealty satellite if it can 
fill the channel with a good one, so if you have  12 visible sats
that may not be important.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
[EMAIL PROTECTED] | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] GPS PRN 32

[Bruce Griffiths]

Poul-Henning Kamp wrote:
 In message [EMAIL PROTECTED], Bruce Griffiths writes:
   
 Bruce Griffiths wrote:
 
 Tom

 My Z3815A sees PRN 32 now albeit as unhealthy.

 Bruce

   
   
 My M12+ T doesn't see SVN 23 (PRN32) although its shares the same antenna.
 

 By default the M12 will not track an unhealty satellite if it can 
 fill the channel with a good one, so if you have  12 visible sats
 that may not be important.

   
Poul

The M12 wasn't tracking 12 satellites, however I didn't count the number
visible.
Will check again in 12 hours or so when SVN23 should again be next visible.

Bruce

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Re: [time-nuts] GPS PRN 32

[Bruce Griffiths]

Poul-Henning Kamp wrote:
 In message [EMAIL PROTECTED], Bruce Griffiths writes:
   
 Bruce Griffiths wrote:
 
 Tom

 My Z3815A sees PRN 32 now albeit as unhealthy.

 Bruce

   
   
 My M12+ T doesn't see SVN 23 (PRN32) although its shares the same antenna.
 

 By default the M12 will not track an unhealty satellite if it can 
 fill the channel with a good one, so if you have  12 visible sats
 that may not be important.

   
The Z3815A GPS receiver is a Furuno receiver with 16 channels.

Bruce

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Re: [time-nuts] GPS PRN 32

[Bruce Griffiths]

Bruce Griffiths wrote:
 Tom

 My Z3815A sees PRN 32 now albeit as unhealthy.

 Bruce

   
My M12+ T doesn't see SVN 23 (PRN32) although its shares the same antenna.

Bruce

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Re: [time-nuts] GPS PRN 32

[Dan Rae]

My Thunderbolt (nor any of the others, of course) cannot see this one at 
present, but TBolt Mon is showing a yellow button indicating incomplete 
or incorrect almanac.   So it knows something's up!
dr


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Re: [time-nuts] GPS PRN 32

[Bruce Griffiths]

Bruce Griffiths wrote:
 Poul-Henning Kamp wrote:
   
 In message [EMAIL PROTECTED], Bruce Griffiths writes:
   
 
 Bruce Griffiths wrote:
 
   
 Tom

 My Z3815A sees PRN 32 now albeit as unhealthy.

 Bruce

   
   
 
 My M12+ T doesn't see SVN 23 (PRN32) although its shares the same antenna.
 
   
 By default the M12 will not track an unhealty satellite if it can 
 fill the channel with a good one, so if you have  12 visible sats
 that may not be important.

   
 
 The Z3815A GPS receiver is a Furuno receiver with 16 channels.

 Bruce

   
Correction:

Looked at wrong datasheet.
Z3815A receiver supposedly has 8 channels.
However it may have a couple of spare channels used for monitoring
untracked SVs.

Currently it tracks 3 and displays 6 untracked.
earlier totals were 3 and 7 resp.

Bruce

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