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Dear Michael,<br>
<br>
Hmmm, the multiband delays (MBD) don't look great. Generally they
should be large are lower elevations and smaller at higher with some
scatter (OV in the SNPLT you sent is about right). So I am worried
about the MBD, I would start by re-running FRING with a higher SNR
cutoff (APARM(7) in FRING) or use MBDLY. To use MBDLY you have to
compute the phases in FRING of CALIB first. <br>
<br>
I had another thought is there one solution scan? You have a lot of
failed solutions and my guess that is because you are observing at
high freq so a large fraction of geodetic targets are not good at
high freq. Also do you see a slope in the POSSM plot before you
apply the DELZN solutions?<br>
<br>
Amy<br>
<br>
<div class="moz-cite-prefix">On 6/22/20 10:24 AM, Michael Rosenthal
via Daip wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAPQDu6TBBCR9k6QWNWEVkuMYKoFegQ+gXc5-4vVLS3wVMOV0+w@mail.gmail.com">
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<div>Good morning,</div>
<div><br>
</div>
<div>We are using AIPS to reduce K-band geodetic data for a
spectral line dataset. We proceeded through most of the
geodetic data reduction steps specified in the CASA guide for
spectral lines and astrometry without issue, but identified a
problem when plotting the output of DELZN.</div>
<div><br>
</div>
<div>For context, we used the source 'J2038+51' as the cal
source for VLBAMPCL with no failed solutions. Solving for
multi-band delay with FRING yielded 3464 good and 1064 failed
solutions, which we thought acceptable. After running the MBD
through SNEDT we had flagged out points such that we were left
with all points having absolute values <~ 1-2 ns. A
screenshot of the SNPLT TV output after running SNEDT is
attached here.</div>
<div>
<div><br>
</div>
<div>The plots of the MBD solutions from TVPL looked
reasonable (I've attached two here as an example). We then
ran DELZN, when we re-ran POSSM with gainu=6, with CL #6
being the table generated by running DELZN, the phase vs.
channel for sources other than J2038+51 are not as flat as
the example in the CASA guide. I've attached two versions of
the POSSM output for the source J0433+05: one using CL #5,
from before we ran SNEDT and DELZN, and one using CL #6.</div>
<div><br>
</div>
<div>This problem persists if we apply CL #6 to other sources
in the geodetic data, and the rest of the sources in the
geodetic data have weaker fringes than J2038+51.</div>
<div><br>
</div>
<div>Are the solutions we have from DELZN appropriate to
proceed with the rest of our data reduction? If not, is
there a way we can resolve this issue? </div>
<div><br>
</div>
<div>Kind regards,</div>
<div>Michael<br>
<div><br>
</div>
-- <br>
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<div dir="ltr"><b>Michael Rosenthal</b>
<div><b><br>
</b></div>
<div>Research Assistant</div>
<div>Center for Astro, Particle, and
Planetary Physics</div>
<div>New York University Abu Dhabi</div>
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<br>
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