From: <Brett.Reid_at_email.protected>
Date: Thu, 15 Mar 2012 21:01:48 +1100

Hi Adam,
Yes I believe it is nanoseconds on the vertical scale and days horizontal.

I don't know of any gear being clocked at 500 Mhz.

It is interesting that the Hobart February plot shows similar steps
although they are probably about 1 nanosecond and Ceduna's March steps
are 2 nanoseconds.

I do not know what it means or if I can afford to be optimistic.

It is good to hear from you Adam.

Regards,
Brett

On 15/03/12 7:07 PM, Adam Deller wrote:
>Hi Brett,
>
>What is the scale on the y axis ("phase"?) of the Ceduna graphs? Is
>it nanoseconds? For the March one, you can see many distinct jumps of
>approximately 2 units, so I'm guessing that is what Jim is referring
>to. Are there any components at the station which are clocked at 500 MHz?
>
>Cheers,
>Adam
>
>On Thu, Mar 15, 2012 at 5:02 AM, Brett Reid <Brett.Reid_at_utas.<!--nospam-->edu.au
><mailto: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/
><http://users.on.net/%7Ecdadsl/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 <mailto:jim.ray_at_noaa.<!--nospam-->gov>>
>Reply-To: Jim.Ray_at_noaa.<!--nospam-->gov <mailto:Jim.Ray_at_noaa.<!--nospam-->gov>
>To: Brett Reid <Brett.Reid_at_utas.<!--nospam-->edu.au
><mailto:Brett.Reid_at_utas.<!--nospam-->edu.au>>
>CC: geodesy_at_ga.<!--nospam-->gov.au <mailto:geodesy_at_ga.<!--nospam-->gov.au>, Warren Hankey
><wjhankey_at_postoffice.<!--nospam-->utas.edu.au
><mailto:wjhankey_at_postoffice.<!--nospam-->utas.edu.au>>, Simon Ellingsen
><Simon.Ellingsen_at_utas.<!--nospam-->edu.au
><mailto:Simon.Ellingsen_at_utas.<!--nospam-->edu.au>>, M & B Bedson
><clouds_at_internode.<!--nospam-->on.net <mailto:clouds_at_internode.<!--nospam-->on.net>>, John
>Dickey <John.Dickey_at_utas.<!--nospam-->edu.au <mailto:John.Dickey_at_utas.<!--nospam-->edu.au>>,
>Jay Blanchard <jayb_at_postoffice.<!--nospam-->utas.edu.au
><mailto:jayb_at_postoffice.<!--nospam-->utas.edu.au>>, Ryan.Ruddick_at_ga.<!--nospam-->gov.au
><mailto:Ryan.Ruddick_at_ga.<!--nospam-->gov.au>
>References: <4F3AEF0C.2050600_at_utas.<!--nospam-->edu.au
><mailto:4F3AEF0C.2050600_at_utas.<!--nospam-->edu.au>>
><4F5EBBCF.7070502_at_utas.<!--nospam-->edu.au <mailto: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
><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 <tel:%2B61%203%206248%205285>
>Mobile 0407 955 283
>email brett.reid_at_utas.<!--nospam-->edu.au <mailto:brett.reid_at_utas.<!--nospam-->edu.au>
>web http://users.on.net/~cdadsl <http://users.on.net/%7Ecdadsl>
>
>
>
>
>--
>!=============================================================!
>Dr. Adam Deller Ph +31 521595766
><tel:%2B31%20521595766>
>Veni Fellow, Astronomy Group Fax +31 521595101
><tel:%2B31%20521595101>
>ASTRON, Oude Hoogeveensedijk 4
>7991 PD Dwingeloo, The Netherlands
>!=============================================================!

-- 
Brett Reid
Observatory Manager, Radio Telescopes
University of Tasmania, School of Mathematics and Physics
Phone 03 6248 5285  or 0407 955 283
Brett.Reid_at_utas.<!--nospam-->edu.au
users.on.net/~cdadsl

Received on 2012-03-15 21:02:25