<div dir="ltr"><div><div><div>Hi Walter,<br><br></div>Thanks for that answer.<br><br></div>Cheers,<br></div>Sam<br></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, May 18, 2017 at 2:04 PM, Walter Brisken <span dir="ltr"><<a href="mailto:wbrisken@lbo.us" target="_blank">wbrisken@lbo.us</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><br>
See the section on "Conventions" in the DiFX manual: <a href="http://www.atnf.csiro.au/vlbi/dokuwiki/lib/exe/fetch.php/difx/difxuserguide.pdf" rel="noreferrer" target="_blank">http://www.atnf.csiro.au/vlbi/<wbr>dokuwiki/lib/exe/fetch.php/dif<wbr>x/difxuserguide.pdf</a><br>
<br>
Quick answer: everything in DiFX uses the opposite convention as the vex file, so the sign in the .v2d file should be opposite.<br>
<br>
-Walter<div class="HOEnZb"><div class="h5"><br>
<br>
On Thu, 18 May 2017, Mark Kettenis wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
From: Hagatiana Andrianomena <<a href="mailto:handrianomena@ska.ac.za" target="_blank">handrianomena@ska.ac.za</a>><br>
Date: Thu, 18 May 2017 11:46:42 +0200<br>
<br>
Hi Mark,<br>
<br>
I have used the clock values from SFXC for example:<br>
# def BD;<br>
# clock_early= 2017y059d13h00m00s : 216.030 usec : 2017y059d14h30m00s<br>
: -2.20e-07 usec/sec;<br>
# enddef;<br>
<br>
My understanding is that DiFX expect the rates in usec/sec which is the<br>
case here, so I have used<br>
that value in the .v2d file, as for the clockEpoch I used<br>
2017y059d14h30m00s here (converted to mjd).<br>
For sure I am having issues with some values I am using, reason I do not<br>
find fringes at some baselines.<br>
</blockquote>
<br>
It is my understanding that DiFX expects proper dimensionless rates<br>
(i.e. sec/sec) so for the example you give above, you'd have to put<br>
-2.20e-13 as the rate into the v2d file. Also, I'm not sure the<br>
clocks in the .v2d file use the same sign convention as the VEX file.<br>
Hopefully one of the DiFX expert can tune in and confirm/deny this.<br>
<br>
Regarding the clock rates. It usually is "safe" to set the clock<br>
rates simply to 0 if you suspect they might be wrong. For most VLBI<br>
stations the clock rates are small enough that there is no significant<br>
decorrelation within a couple of seconds. That might not apply to NK<br>
though as I understand it uses a Rubidium clock.<br>
<br>
Good luck,<br>
<br>
Mark<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
With regards to EOP, I used the values from NASA.<br>
<br>
Thanks for your reply Richard.<br>
<br>
Regards,<br>
Sam<br>
<br>
<br>
On Thu, May 18, 2017 at 1:08 AM, Richard Dodson <<a href="mailto:richard.dodson@uwa.edu.au" target="_blank">richard.dodson@uwa.edu.au</a>><br>
wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi<br>
<br>
I agree with all the above that the most likely source of a high delay<br>
offset is either incorrect position for the antenna in VEX, or a<br>
mis-translated value for the initial delay offset. If there are no fringes<br>
to any station it is unlikely to be antenna positions (as one being wrong<br>
is possible, but some of the ones you are using are very well established),<br>
so I put my money on Mark's suggestion. But another possible thing to<br>
check, if the above are correct, are the Earth Orientation Parameters. If<br>
these are wrong you essentially have introduced an offset in all the<br>
antenna positions.<br>
<br>
happy hunting!<br>
Richard<br>
<br>
On Thu, May 18, 2017 at 12:33 AM, Hagatiana Andrianomena <<br>
<a href="mailto:handrianomena@ska.ac.za" target="_blank">handrianomena@ska.ac.za</a>> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Mark,<br>
<br>
Many thanks for that very useful information.<br>
I will double-check the $CLOCK values I was<br>
using.<br>
<br>
Cheers,<br>
Sam<br>
<br>
On Wed, May 17, 2017 at 5:02 PM, Mark Kettenis <<a href="mailto:kettenis@jive.eu" target="_blank">kettenis@jive.eu</a>> wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
From: Hagatiana Andrianomena <<a href="mailto:handrianomena@ska.ac.za" target="_blank">handrianomena@ska.ac.za</a>><br>
Date: Mon, 15 May 2017 08:51:59 +0200<br>
</blockquote>
<br>
Sam,<br>
<br>
Note that if you are using $CLOCK parameters from a correlation with<br>
SFXC, the rates may not be specified in a form that DiFX expects. If<br>
the "unit" isn't specified, SFXC will interpret the rate as usec/sec,<br>
whereas DiFX will interpret the rate as sec/sec.<br>
<br>
Cheers,<br>
<br>
Mark<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Cormac,<br>
<br>
Please see attached the vex. I am interested in EF-YS-NK-HH-O8.<br>
<br>
cheers,<br>
Sam<br>
<br>
On Mon, May 15, 2017 at 7:45 AM, Cormac Reynolds<br>
</blockquote>
<cormac.reynolds@csiro.au><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
hi Sam,<br>
<br>
just following up on Adam's point. The most common cause of a very<br>
</blockquote></blockquote>
high<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
residual fringe rate (as yours appears to be) in an otherwise<br>
</blockquote></blockquote>
functioning<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
array is an error in the station position(s). If you send the vex<br>
</blockquote></blockquote>
file you<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
used, and the stations you are interested in, it should be<br>
</blockquote></blockquote>
straightforward<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
to say if that is a likely cause or not.<br>
<br>
cheers,<br>
Cormac.<br>
<br>
On 13/05/17 19:57, Hagatiana Andrianomena wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi Adam,<br>
<br>
Many thanks for your explanations.<br>
<br>
Cheers,<br>
Sam<br>
<br>
On Sat, May 13, 2017 at 1:37 PM, Adam Deller <<br>
</blockquote></blockquote></blockquote>
<a href="mailto:adeller@astro.swin.edu.au" target="_blank">adeller@astro.swin.edu.au</a><br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<mailto:<a href="mailto:adeller@astro.swin.edu.au" target="_blank">adeller@astro.swin.edu<wbr>.au</a>>> wrote:<br>
<br>
Hi Sam,<br>
<br>
Integration time will affect the maximum fringe rate you are<br>
sensitive to. Shorter integrations = higher fringe rate before<br>
</blockquote></blockquote></blockquote>
you<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
lose signal due to decorrelation. But normally this is not a<br>
limitation. I would be fairly surprised if a 1 second<br>
</blockquote></blockquote></blockquote>
integration<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
time was a problem (unless there is an issue with the observing<br>
setup).<br>
<br>
Spectral resolution will affect the maximum residual delay you<br>
</blockquote></blockquote></blockquote>
are<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
sensitive too. Finer spectral resolution = larger delay before<br>
</blockquote></blockquote></blockquote>
you<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
lose signal due to decorrelation.<br>
<br>
These are not DiFX-specific things, but general to radio<br>
interferometers / correlators. To know what values are<br>
</blockquote></blockquote></blockquote>
reasonable,<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
you need to know your instrument and what the expected residual<br>
fringe rate and delay are.<br>
<br>
Cheers,<br>
Adam<br>
<br>
On 12 May 2017 at 23:59, Hagatiana Andrianomena<br>
<<a href="mailto:handrianomena@ska.ac.za" target="_blank">handrianomena@ska.ac.za</a> <mailto:<a href="mailto:handrianomena@ska.ac.za" target="_blank">handrianomena@ska.ac.z<wbr>a</a>>><br>
</blockquote></blockquote></blockquote>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<br>
Hi DiFX users,<br>
<br>
I got a question regarding the integration time in the<br>
</blockquote></blockquote></blockquote>
setup:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
SETUP default<br>
{<br>
tInt = 1.000000<br>
fftSpecRes = 0.12500000<br>
specRes = 0.12500000<br>
doPolar = True<br>
maxNSBetweenACAvg = 2000000<br>
}<br>
<br>
I got this default setup by running oms2v2d using the .oms<br>
</blockquote></blockquote></blockquote>
file<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
from the experiment. When running the difx I got no fringe<br>
</blockquote></blockquote></blockquote>
but<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
from changing the tInt to<br>
0.08 and both fftSpecRes and specRes the result seems to<br>
</blockquote></blockquote></blockquote>
suggest<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
I got fringe (see plot attached).<br>
<br>
I am not quite sure whether it is a naive question but I<br>
</blockquote></blockquote></blockquote>
wonder<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
if there is a simple rule of thumb to get the right values<br>
</blockquote></blockquote></blockquote>
of<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
those parameters in order to get fringe. I do not have much<br>
experience with DiFX I must say though.<br>
<br>
Regards,<br>
Sam<br>
<br>
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--<br>
!=============================<wbr>==============================<wbr>==!<br>
Dr. Adam Deller<br>
ARC Future Fellow, Senior Lecturer<br>
Centre for Astrophysics & Supercomputing<br>
Swinburne University of Technology<br>
John St, Hawthorn VIC 3122 Australia<br>
phone: <a href="tel:%2B61%203%209214%205307" value="+61392145307" target="_blank">+61 3 9214 5307</a> <tel:+61%203%209214%205307><br>
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-------------------------<br>
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International Centre for Radio Astronomy Research<br>
University of Western Australia<br>
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-------------------------<br></div></div><span class="HOEnZb"><font color="#888888">
Walter Brisken<br>
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Long Baseline Observatory<br>
<a href="tel:%28505%29-234-5912" value="+15052345912" target="_blank">(505)-234-5912</a><br>
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