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Satellite Failure Behind GPS Timing Anomaly (itnews.com.au)
Bismillah writes: The recent 13-microsecond timing anomaly was caused by a satellite failure triggering a "software issue", the USAF 50th Space Wing has confirmed. Such an error is large enough to cause navigation errors of up to 4 km. Luckily, no issues with GPS guided munition were reported.
Reader donaggie03 adds a link to the official explanation from Rick Hamilton, Executive Secretariat of the Civil Global Positioning System Service Interface Committee. From Hamilton's email:
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.
In classic Slashdot style, the headline says a hardware failure and TFA says a software bug temporarily mitigated by an operational procedures change.
Just dreaming, but it might be nice if the poster read TFA so the rest of us don't have to?
You are funny, in a deranged sort of way...
You do realize that the current crop of missile based nuclear weapons are pretty much independent of the GPS system, having been developed BEFORE GPS was built by about a decade.
GPS launches started back in 1978 and it was a couple of years before we had enough satellites in orbit to be useful. So GPS came on line sometime after 1980.
The LGM-30 Block 3 is our current land based ICBM and it went into service a decade before in about 1970, but really is a refinement of a 1962 missile. It is guided by an inertial navigation system and is totally independent of outside input while in flight, so it doesn't need to use GPS.
The current Navy missile is the Trident 3 (USM-96) which uses a guidance system that is both inertial and refines its guidance using astronomical observations in flight. It was developed in the late 70s, but does NOT use GPS during flight for guidance. It too predates a working GPS constellation by at least a decade.
If the Russians are messing with GPS in hopes of disrupting our nuclear capability, they are a lot more stupid than I ever imagined... The reality is that GPS is not used for positioning information for any kind of nuclear weapon delivery system and it's not used as an exclusive positioning source for any critical military application. This is mainly because the system is already known to be vulnerable to upset and jamming, so alternatives have been considered, alternate equipment obtained, personnel trained in how NOT to depend on GPS.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Nope, because if you were using a GPS approach, you'd have checked your destination for sufficient GPS satellite coverage. RAIM (Receiver autonomous integrity monitoring) is something a safety-critical GPS receiver provides. If there are less than 24 satellites in the constellation, it MUST be consulted.
Basically when you have more satellites than needed to acquire a GPS fix, the additional satellites give you two things - one, an oversolution (Finding GPS location is solving a system of equations - if you have three satellites, you can do an X, Y and Time and get a 2D fix. To get a 3D fix, you need four satellites. If you have more satellites, they can be used to hone your position further.
The second use is to detect bad satellites - by comparing the results with one satellite out of the calculations at the time, you can detect the bad satellite because your calculations with the satellite in will be vastly different than if it is out. This is what RAIM does, and for GPS approaches, you must have sufficient satellite coverage for RAIM to operate and work. At a minimum, it's +1 more satellite