[time-nuts] GPS jump

Neil Schroeder gigneil at gmail.com
Sat Oct 11 01:00:11 EDT 2014


I'm trying to determine semantics and I was likely mistaken.

They regularly update them both a variety of technologies - TWTCC and
others. Then DC of course sends to COS.

 Is it actually possible to phase lock two oscillators together cross the
distance from DC  to  Colorado Springs? (2400 kilometers or so). ?


On Friday, October 10, 2014, Brian Inglis <Brian.Inglis at systematicsw.ab.ca>
wrote:

> On Oct 9, 2014, at 7:43 PM, Jim Palfreyman <jim77742 at gmail.com> wrote:
>>>
>>
>  We look after 5 separate hydrogen masers spread all over Australia and we
>>>> collect tic phases between the masers and the GPS.
>>>>
>>>> On around ~Oct 7 we have noticed that the normal steady straight line
>>>> (with
>>>> standard daily noise) took a noticeable downward turn - on all 5 masers.
>>>>
>>>
>  On 2013-10-03 05:33, Jim Palfreyman wrote:
>>>>
>>>
>  Noticed an above average bump in our H-Maser vs GPS graphs - from sites
>>>>> all over Australia.
>>>>>
>>>>> Recent coronal mass ejection or US government shutdown not updating
>>>>> GPS?
>>>>> Anyone else seen it?
>>>>>
>>>>
>  drop out gap between about 04.21-04.26 UTC?
>>>> clockstats.20131003:
>>>> 56568 15684.876 127.127.20.4 $GPRMC 042124 A ...
>>>> 56568 16004.862 127.127.20.4 $GPRMC 042644 A ...
>>>> peerstats.20131003:
>>>> 56568 15684.876 127.127.20.4 961a -0.000002270 ... 0.000005344
>>>> 56568 16004.862 127.127.20.4 961a -0.000013150 ... 0.000015721
>>>> loopstats.20131003:
>>>> 56568 15684.876 -0.000002270 0.899 0.000007071 0.000070 4
>>>> 56568 16004.862 -0.000013150 0.898 0.000008830 0.000114 4
>>>>
>>>
>
>>>> Did anyone else who tracks H-masers notice this as well?
>>>>
>>>> Is it JPL making corrections?
>>>>
>>>
>  Le 10 oct. 2014 à 03:09, Bob Camp a écrit :
>>
>
>  GPS is steered by the Air Force last time I checked.
>>> A really good place to check is the NIST Time and Frequency pages that
>>> show both real time and historical data for each GPS sat compared to NIST
>>> time:
>>> http://www.nist.gov/pml/div688/grp40/gpsarchive.cfm
>>> Hopefully it’s accessible via that link from a variety of locations.
>>> Since the NIST data is independent of the steering (two different
>>> outfits involved) it should not be vulnerable to a “our ground segment
>>> broke and we steered everything to match” sort of error.
>>>
>>
> On 2014-10-09 23:06, mike cook wrote:
>
>>    I remember Jim reported a similar issue back in october last year:
>>
>
>     That dates are close enough to make you wonder if it is not part of
>> some cycle.
>>
>
> From: http://www.usno.navy.mil/USNO/time/gps/gps-info
> GPS SYSTEM TIME
> GPS system time is given by its Composite Clock (CC).
> The CC or "paper" clock consists of all operational Monitor Station and
> satellite
> frequency standards. GPS system time, in turn, is referenced to the Master
> Clock
> (MC) at the USNO and steered to UTC(USNO) from which system time will not
> deviate
> by more than one microsecond. The exact difference is contained in the
> navigation
> message in the form of two constants, A0 and A1, giving the time
> difference and
> rate of system time against UTC(USNO,MC).
>
> Page also gives links to GPS time data ftp://tycho.usno.navy.mil/pub/
> gps/utcgps30.dat
> which shows a 2ns jump in UTC(USNO)-GPS smoothed over 2 days from Oct 7-8,
> but that
> appears normal; the <1ns differences from Oct 2-7 appear anomalous.
>
> Looking at the NIST 10 min data, from Oct 3-8 the gap between GPS samples
> and NIST
> closed about 1.5ns/day, dropping now to about .5ns/day: the graph shows
> the values
> sliding down to the right, and now levelling off about zero.
>
> So are NIST and USNO steering each other?
>
> --
> Take care. Thanks, Brian Inglis
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