[Fwd: Re: Ceduna clock maintenance]
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From: <Brett.Reid_at_email.protected>
Date: Thu, 15 Mar 2012 15:02:00 +1100
Simon suggested I forward this response to the wider VLBI group.
It is the GPS guy's response to my questions about whether improvements
are observable from the GPS data to their maser synchronised clock,
since the work Warren and I did in the week prior to the last LBA run at
Ceduna.
The reason it is being forwarded to this group is that there may be some
of you who can help us interpret the plots/comments and determine if
this type of data can give us a check for future on the Ceduna phase
stability problem as an alternative to waiting for VLBI data
correlation. After all, this GPS data is already being continuously
monitored. Simon and I were unsure of what "phase slips in units of
(1cycle/2ns)" comment means, after taking a quick look.
Please let me know if you have ideas on using this data as a check for
Ceduna phase stability or if you have questions also that I can pass on
to Jim Ray.
Regards,
Brett
Please note that Jim Ray's message below refers to attachments. Because
of the size restriction of posts to this mail list, I have stripped of
the .pdf attachments and placed them in the following folder available
on the web:
http://users.on.net/~cdadsl/CdMaser/gpsPlots/
-------- Original Message --------
Subject: Re: Ceduna clock maintenance
Date: Tue, 13 Mar 2012 08:26:04 -0400
From: Jim.Ray <jim.ray_at_noaa.<!--nospam-->gov>
Reply-To: Jim.Ray_at_noaa.<!--nospam-->gov
To: Brett Reid <Brett.Reid_at_utas.<!--nospam-->edu.au>
CC: geodesy_at_ga.<!--nospam-->gov.au, Warren Hankey <wjhankey_at_postoffice.<!--nospam-->utas.edu.au>,
Simon Ellingsen <Simon.Ellingsen_at_utas.<!--nospam-->edu.au>, M & B Bedson
<clouds_at_internode.<!--nospam-->on.net>, John Dickey <John.Dickey_at_utas.<!--nospam-->edu.au>, Jay
Blanchard <jayb_at_postoffice.<!--nospam-->utas.edu.au>, Ryan.Ruddick_at_ga.<!--nospam-->gov.au
References: <4F3AEF0C.2050600_at_utas.<!--nospam-->edu.au> <4F5EBBCF.7070502_at_utas.<!--nospam-->edu.au>
Hi Brett,
Attached are monthly clock plots for CEDU and fyi HOB2 also, in both
cases for February and for March so far. These come from the site:
https://goby.nrl.navy.mil/IGStime/igrt_plots_monthly.php
for the monthly IGS Rapid (IGRT) plots, or the general NRL site:
https://goby.nrl.navy.mil/IGStime/index.php
I converted from the original ps plot format to pdf for your convenience.
During Feb., there were a couple of very major clock offset resets at
CEDU (several x 10^5 ns) so it is not possible to see any details of
the clock stability during Feb without going back to the raw clock data
and making zoom plots. But it's clear that the reset you report below
is visible.
The Mar. plot for CEDU shows the detailed time variability for the 1st
11 days of this month. (The plot will update at about 17:00 UTC today
to add results for 12 March.) I leave it to you to decide if this is
the expected stability. It would normally be considered rather poor
for an H-maser itself (daily changes at the 1 ns level) but I have no
idea of the total timing chain at the station. This level is definitely
sufficient for VLBI or GPS though.
The rather odd, sharp steps in the time domain of about 2 ns each time
are not normal. It would make me wonder about a possible component in
the timing chain that suffers phase slips in units of (1cycle/2ns),
possibly a freq multiplier for instance. I forget the nature of the
problems we discussed a while back.
The Hobart plots are included just FYI.
Hope this helps. Best regards,
--Jim
On 3/12/2012 11:15 PM, Brett Reid wrote:
>Dear Jim and Ryan,
>We disturbed the clock signals during maintenance at Ceduna that would have
>affected your GPS data mostly during the following period:
>
>28/2/12 8.30am till 28/2/12 8.30 pm local time
>058/2200 UT till 059/1000 UT.
>
>This was when we replaced power supplies that might affect the clock
>distribution system.
>
>We left the site on 1/3/12
>
>We have done VLBI since and do not yet have results from the correlator.
>
>I am wondering if you see an improvement of Ceduna's clock stability looking at
>the GPS data since 059/1000 UT.
>
>I tried looking at a link you have given me previously but the files do not
>seem to be where they used to be.
>The link you gave me previously was:
>https://goby.nrl.navy.mil/IGStime/filelisting_monthlyplots.php?D1=IGRT&D2=plots_monthly
>
>
>And anyway, I am not sure I would know how to interpret the plots that used to
>be there, so I would appreciate your comment on whether there has been a recent
>improvement in the GPS data due to clock.
>
>Also Ryan, I shall be visiting Katherine for the last week of March. Let me
>know if anything needs doing there.
>
>Regards,
>Brett.
>
>
>
>Brett Reid wrote:
>>Dear Ryan and GA Geodesy people,
>>Warren and I shall be at Ceduna performing work on the VLBI antenna and the
>>clock distribution system. We are there from 20/2/12 1000 UT through till
>>1/3/12 0000 UT.
>>
>>I shall take notes of when we are doing work that could affect your GPS
>>receiver clock and give you a summary so you can know in more detail what
>>periods of GPS data might have been affected.
>>
>>We want to solve a clock problem still affecting VLBI data (and possibly your
>>GPS data).
>>
>>Regards,
>>Brett
>>
>
>
Date: Thu, 15 Mar 2012 15:02:00 +1100
Simon suggested I forward this response to the wider VLBI group.
It is the GPS guy's response to my questions about whether improvements
are observable from the GPS data to their maser synchronised clock,
since the work Warren and I did in the week prior to the last LBA run at
Ceduna.
The reason it is being forwarded to this group is that there may be some
of you who can help us interpret the plots/comments and determine if
this type of data can give us a check for future on the Ceduna phase
stability problem as an alternative to waiting for VLBI data
correlation. After all, this GPS data is already being continuously
monitored. Simon and I were unsure of what "phase slips in units of
(1cycle/2ns)" comment means, after taking a quick look.
Please let me know if you have ideas on using this data as a check for
Ceduna phase stability or if you have questions also that I can pass on
to Jim Ray.
Regards,
Brett
Please note that Jim Ray's message below refers to attachments. Because
of the size restriction of posts to this mail list, I have stripped of
the .pdf attachments and placed them in the following folder available
on the web:
http://users.on.net/~cdadsl/CdMaser/gpsPlots/
-------- Original Message --------
Subject: Re: Ceduna clock maintenance
Date: Tue, 13 Mar 2012 08:26:04 -0400
From: Jim.Ray <jim.ray_at_noaa.<!--nospam-->gov>
Reply-To: Jim.Ray_at_noaa.<!--nospam-->gov
To: Brett Reid <Brett.Reid_at_utas.<!--nospam-->edu.au>
CC: geodesy_at_ga.<!--nospam-->gov.au, Warren Hankey <wjhankey_at_postoffice.<!--nospam-->utas.edu.au>,
Simon Ellingsen <Simon.Ellingsen_at_utas.<!--nospam-->edu.au>, M & B Bedson
<clouds_at_internode.<!--nospam-->on.net>, John Dickey <John.Dickey_at_utas.<!--nospam-->edu.au>, Jay
Blanchard <jayb_at_postoffice.<!--nospam-->utas.edu.au>, Ryan.Ruddick_at_ga.<!--nospam-->gov.au
References: <4F3AEF0C.2050600_at_utas.<!--nospam-->edu.au> <4F5EBBCF.7070502_at_utas.<!--nospam-->edu.au>
Hi Brett,
Attached are monthly clock plots for CEDU and fyi HOB2 also, in both
cases for February and for March so far. These come from the site:
https://goby.nrl.navy.mil/IGStime/igrt_plots_monthly.php
for the monthly IGS Rapid (IGRT) plots, or the general NRL site:
https://goby.nrl.navy.mil/IGStime/index.php
I converted from the original ps plot format to pdf for your convenience.
During Feb., there were a couple of very major clock offset resets at
CEDU (several x 10^5 ns) so it is not possible to see any details of
the clock stability during Feb without going back to the raw clock data
and making zoom plots. But it's clear that the reset you report below
is visible.
The Mar. plot for CEDU shows the detailed time variability for the 1st
11 days of this month. (The plot will update at about 17:00 UTC today
to add results for 12 March.) I leave it to you to decide if this is
the expected stability. It would normally be considered rather poor
for an H-maser itself (daily changes at the 1 ns level) but I have no
idea of the total timing chain at the station. This level is definitely
sufficient for VLBI or GPS though.
The rather odd, sharp steps in the time domain of about 2 ns each time
are not normal. It would make me wonder about a possible component in
the timing chain that suffers phase slips in units of (1cycle/2ns),
possibly a freq multiplier for instance. I forget the nature of the
problems we discussed a while back.
The Hobart plots are included just FYI.
Hope this helps. Best regards,
--Jim
On 3/12/2012 11:15 PM, Brett Reid wrote:
>Dear Jim and Ryan,
>We disturbed the clock signals during maintenance at Ceduna that would have
>affected your GPS data mostly during the following period:
>
>28/2/12 8.30am till 28/2/12 8.30 pm local time
>058/2200 UT till 059/1000 UT.
>
>This was when we replaced power supplies that might affect the clock
>distribution system.
>
>We left the site on 1/3/12
>
>We have done VLBI since and do not yet have results from the correlator.
>
>I am wondering if you see an improvement of Ceduna's clock stability looking at
>the GPS data since 059/1000 UT.
>
>I tried looking at a link you have given me previously but the files do not
>seem to be where they used to be.
>The link you gave me previously was:
>https://goby.nrl.navy.mil/IGStime/filelisting_monthlyplots.php?D1=IGRT&D2=plots_monthly
>
>
>And anyway, I am not sure I would know how to interpret the plots that used to
>be there, so I would appreciate your comment on whether there has been a recent
>improvement in the GPS data due to clock.
>
>Also Ryan, I shall be visiting Katherine for the last week of March. Let me
>know if anything needs doing there.
>
>Regards,
>Brett.
>
>
>
>Brett Reid wrote:
>>Dear Ryan and GA Geodesy people,
>>Warren and I shall be at Ceduna performing work on the VLBI antenna and the
>>clock distribution system. We are there from 20/2/12 1000 UT through till
>>1/3/12 0000 UT.
>>
>>I shall take notes of when we are doing work that could affect your GPS
>>receiver clock and give you a summary so you can know in more detail what
>>periods of GPS data might have been affected.
>>
>>We want to solve a clock problem still affecting VLBI data (and possibly your
>>GPS data).
>>
>>Regards,
>>Brett
>>
>
>
-- Brett Reid Observatory Manager, Radio Astronomy Group University of Tasmania, School of Mathematics and Physics Phone +61 3 6248 5285 Mobile 0407 955 283 email brett.reid_at_utas.<!--nospam-->edu.au web http://users.on.net/~cdadslReceived on 2012-03-15 15:02:32