[ANSS-netops] Altus/K2 timing issue

[Jon Rusho]

We've done some testing with an impacted K2 using software-based time 
correction and a Nanometrics Centaur.   Both were fed the same 
square-wave input signal and compared.
Attached are two tracings from Swarm.   The left one is from the K2 with 
software correction, the right from the Nanometrics.   The red vertical 
line shows the same time in both windows.

For Earthworm users, I'm working with ISTI to get the code change put 
into the svn repository.

Note: the reason this rollover glitch hit early is based on the last 
firmware revision from Kinemetrics.   The firmware fix for the 1999 
rollover was put out 40 weeks before the actual rollover.   That fix 
expired 40 weeks before the upcoming actual rollover in 2019.    Also, 
this doesn't seem to impact all K2 and Etnas.   20 of our K2's were hit, 
but another 20+ are fine.


--jon

On 7/2/18 9:44 AM, Jon Rusho wrote:
> UUSS experienced an early roll-over of the GPS 1024-week counter in 
> many of our Kinemetrics K2 instruments this weekend.   Looking at 
> IRIS, this appears to have also impacted other networks.   The problem 
> manifested itself as waveform data being timestamped in 1998 instead 
> of 2018.
>
> I'm testing a software fix in the k2ew Earthworm modules.   For data 
> that comes in timestamped between 1998 and 01-July-2018, I shifted the 
> time by 1024 weeks (619315200 seconds).
>
> My question to all of you, is this the correct shift or am I missing 
> something?
>
>
> More info on the GPS rollover: 
> https://spectracom.com/resources/blog/lisa-perdue/2018/gps-2019-week-rollover-what-you-need-know
>
>
>
> Thanks
> --jon
>
>
>
>


-- 
===================================
Jon Rusho
Seismic Network Engineer
University of Utah Seismograph Stations

jon at seis.utah.edu
801-585-5523

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