Re: [Fwd: Re: Ceduna clock maintenance]
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From: <c.reynolds_at_email.protected>
Date: Fri, 16 Mar 2012 13:58:48 +0800
hi Brett,
those data could be very interesting. Just eyeballing the plots, it's
pretty clear that the short term variance on the Ceduna data is much
larger than the short term variance on the Hobart data. You can
clearly see significant point to point fluctuations about the long
term trend in the Ceduna data, but the Hobart data are much smoother.
It would be very interesting to get access to the raw data to zoom in
more precisely on the short time scales. It might also be instructive
to get some data that overlap with VLBI runs (say last November, which
we have mostly correlated already). If those 1-2 ns jumps are due to
the maser, they might be visible in the delays from the pipeline
analysis.
cheers,
Cormac.
On 15 March 2012 12:02, Brett Reid <Brett.Reid_at_utas.<!--nospam-->edu.au> wrote:
>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/~cdadsl
>
Date: Fri, 16 Mar 2012 13:58:48 +0800
hi Brett,
those data could be very interesting. Just eyeballing the plots, it's
pretty clear that the short term variance on the Ceduna data is much
larger than the short term variance on the Hobart data. You can
clearly see significant point to point fluctuations about the long
term trend in the Ceduna data, but the Hobart data are much smoother.
It would be very interesting to get access to the raw data to zoom in
more precisely on the short time scales. It might also be instructive
to get some data that overlap with VLBI runs (say last November, which
we have mostly correlated already). If those 1-2 ns jumps are due to
the maser, they might be visible in the delays from the pipeline
analysis.
cheers,
Cormac.
On 15 March 2012 12:02, Brett Reid <Brett.Reid_at_utas.<!--nospam-->edu.au> wrote:
>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/~cdadsl
>
-- ---------------------------------------------------- Cormac Reynolds Phone: +61 8 9266 3785 Fax: +61 8 9266 9246 email: c.reynolds_at_curtin.<!--nospam-->edu.au ----------------------------------------------------Received on 2012-03-16 16:59:28