Hi,
Any comments on this email exchange between our Deputy Director and an
observatory engineer? (I would presume the issue is not directly
pertinent to leap seconds.)
Systems at the observatory also rely on NTP, of course, but certainly
GPS is widely deployed throughout our infrastructure at remote
locations.
Thanks!
Rob Seaman
National Optical Astronomy Observatory
--
Begin forwarded message:
Subject: RE: Problems with GPS
Bob,
We are an institution that heavily relies on accurate time, and GPS
is the preferred if not the only way of synchronizing our clocks. In
our facilities we use a large number of GPS time receivers for a
“mission critical” function. Those units are made by different
manufacturers over different periods of time. As the article states,
the GPS team does not control what manufacturers do, and on this
opportunity an ICD was issued for manufacturers to provide updates
for their equipment.
Given that there are incompatibility issues with the new GPS
standards I would recommend for the person in charge of each GPS
time receiver to contact the manufacturer and inquire about the
status of the particular model in use and update the firmware if
necessary. Case the manufacturer no longer exists or the unit is not
upgradable it would be prudent to check the unit against a certified
unit. At this time also seems appropriate conducting a deeper
investigation regarding the future of the GPS standards and
compatibility issues so nobody gets hit without advice.
I hope this helps,
Oliver
Subject: Re: Problems with GPS
Thanks for the heads up Oliver. Can you tell us what it means?
-Bob
Problems with GPS Ground Control Software Update: AEP 5.5C
February 8, 2010
The GPS Wing and 2SOPS (2nd Space Operations Squadron) initiated a
software update of the ground command and control (C2) system for
GPS on January 11, 2010. The update has not gone as smoothly as
planned.
There appear to be two core problems with the software update, one
affecting military selective availability anti-spoofing module
(SAASM) receivers, and the other affecting timing receivers. The
problems have reached such an extent that the GPS Wing has issued a
unique Notice Advisory to NAVSTAR User (NANU) for civilian and
commercial GPS users and for military users, asking for user comments.
See here for the first NANU, issued January 24.
The Air Force has now issued a second NANU through the GPS
Operations Center (GPSOC), for military users, again asking for user
comments: "Attention military users with SAASM receivers. For
information about an anomaly on a limited number of these receivers,
please go to . . . " and so on. "Also reference previous NANUs
2010002, 2010011, 2010016, 2010018."
History of Problems. The Architecture Evolution Plan (AEP) software
provided to the Air Force by Boeing (designated single prime
integrator for AEP in 2001, with Lockheed Martin subcontracted to
continue the development) has generated at least two previous major
SNAFUs, one involving the inability to upload nav data to seven
satellites, and one involving non-compliant international receivers.
In September 2007, when the phased transition of the 22-year-old
Legacy GPS Master Control Station (MCS) to the AEP control segment
became operational, the Air Force described its implementation "like
changing the engine on a car while it's speeding down the freeway
going 65 miles per hour." Apparently either some dropped parts now
litter that freeway, or some gears, somewhere, are not meshing
properly.
The following comments are drawn from Don Jewell’s Defense
newsletter, to appear later this week. For a free subscription,
visit GPS World’s newsletter subscriber page,
“The GPS is so ubiquitous and there are so many global receiver
manufacturers, with so many different receivers on the market today
that, not surprisingly, the GPS Wing has been unable to keep track.
"This is such a Herculean task, and therefore instead of checking
and certifying every GPS receiver manufactured, prior to activating
the software update, the GPS Wing issued an updateable ICD or
Interface Control Document that all receiver manufacturers use as a
voluntary guide to determine compliance.
"However, even the ICD leaves room for interpretation and is more
ambiguous than the GPS Wing intended, so it should come as no
surprise that there were and are still receiver issues following the
latest AEP update. The GPS Wing is currently receiving more help
than they think they need, but this too shall pass; it will just
take time. The GPS Wing did not revert to AEP 5.4 (the previous
version) because of the upcoming IIF-SV1 launch. The scheduled
sequential AEP 5.5C and AEP 5.5D updates are required before the
ground control segment can adequately control the more advanced
capabilities of the IIF satellites.
"The actionable aspect of this update and NANU is that if you are
experiencing any problems or glitches with your GPS receiver that
occurred after the 11 January update, then you should notify the
2SOPS if it is a military receiver and the NAVCEN if it is a
civilian or commercial receiver. The original deadline as 29 January
2010, but I have it on good authority that reports are still being
received. So, if you have a GPS receiver issue, please report it.
"Military users can find additional information on the GPSOC SIPRNet
(classified) website at http://gpsoc.afspc.af.smil.mil. If you don’t
have access to this classified military site, then access the
unclassified and unsecured military website at http://gps.afspc.af.mil/gpsoc
or the secure but unclassified military website at https://gps.afspc.af.mil
. You may also call the GPSOC at (military switch) DSN 560-2541, or
commercial 719-567-2541. You can also communicate using their email
address:gps_supp...@schriever.af.mil. As an alternate contact the
Joint Space Operations Center at (military switch) DSN 276-3514 or
commercial 805-606-3514. Email the JSpOC at jspoccombat...@vandenberg.af.mil
.
"For civil and commercial users the U.S. Coast Guard Navigation
Center’s address is NAVCEN MS7310, 7323 Telegraph Road, Alexandria,
VA 20598-7310 and you can contact them by telephone at (703)
313-5900 or go to their comprehensive website at http://www.navcen.uscg.gov/
.”
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