Jim,

On 01/28/2016 01:22 PM, jimlux wrote:
On 1/27/16 11:46 PM, Magnus Danielson wrote:
Fellow time-nuts,

Here is the official statement.

Cheers,
Magnus


I know we're all time-nuts here and not position-nuts.  The thing in the
statement that was intriguing was about GPS guided munitions.

13.7 microseconds is about 4.5 km.

I've not been following this discussion too closely, but were the nav
solutions from the GPS steady and continuous during the event (that is,
was just a time discontinuity).  I'm guessing that since the problem was
only in the "how to convert from GPS to UTC" parameters that the nav
solution was steady.

That is exactly what Meinbergs research as presented by Martin shows.
In particular, it's the A0 coefficient of the GPS to UTC conversion message which is out of tune.

And this brings up an interesting question. On receivers that provide a
1pps, do they bring out the 1pps on GPS time or on UTC time.  I suspect
some are GPS and some are UTC.

You can configure, most of them would default to UTC and in my experience, many systems wants UTC.

And, did this "ripple in the force" cause all those NTP synchronized
clocks to hiccup (if a NTP ticker is UTC driven vs GPS driven)

NTP bumping around 13,7 us... I'm not sure I *really* care for most usage.

Oh... not to speak about telecom and broadcast networks. When national TV broadcast networks suffers greatly, we start to care about these things. *GREATLY*

Cheers,
Magnus



-------- Forwarded Message --------
Subject: CGSIC: FW: Official Press Release - GPS Ground System Anomaly
Date: Thu, 28 Jan 2016 01:13:13 +0000
From: Civil Global Positioning System Service Interface Committee
(CGSIC) <cg...@cgls.uscg.mil>
Reply-To: cg...@cgls.uscg.mil
To: cg...@cgls.uscg.mil <cg...@cgls.uscg.mil>

All CGSIC:

Air Force Official Press Release - GPS Ground System Anomaly

    On 26 January at 12:49 a.m. MST, the 2nd Space Operations Squadron
at the
50th Space Wing, Schriever Air Force Base, Colo., verified users were
experiencing GPS timing issues.  Further investigation revealed an
issue in
the Global Positioning System ground software which only affected the
time
on legacy L-band signals. This change occurred when the oldest
vehicle, SVN
23, was removed from the constellation. While the core navigation systems
were working normally, the coordinated universal time timing signal
was off
by 13 microseconds which exceeded the design specifications. The issue
was
resolved at 6:10 a.m. MST, however global users may have experienced GPS
timing issues for several hours.  U.S. Strategic Command's Commercial
Integration Cell, operating out of the Joint Space Operations Center,
effectively served as the portal to determine the scope of commercial
user
impacts.  Additionally, the Joint Space Operations Center at
Vandenberg AFB
has not received any reports of issues with GPS-aided munitions, and has
determined that the timing error is not attributable to any type of
outside
interference such as jamming or spoofing.  Operator procedures were
modified
to preclude a repeat of this issue until the ground system software is
corrected, and the 50th Space Wing will conduct an Operational Review
Board
to review procedures and impacts on users. Commercial and Civil users who
experienced impacts can contact the U.S. Coast Guard Navigation Center at
(703) 313-5900.
V/R
Rick Hamilton
CGSIC Executive Secretariat
GPS Information Analysis Team Lead
U.S. Coast Guard Navigation Center
703-313-5930





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