[daip] Jagged phases after running DELZN on geodetic data

[Michael Rosenthal]

Good morning,

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.

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.

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.

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.

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?

Kind regards,
Michael

-- 
*Michael Rosenthal*

Research Assistant
Center for Astro, Particle, and Planetary Physics
New York University Abu Dhabi
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listmgr.nrao.edu/pipermail/daip/attachments/20200622/b97cb960/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: TVPL_DELZN_4.png
Type: image/png
Size: 106139 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/daip/attachments/20200622/b97cb960/attachment-0005.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: TVPL_DELZN_6.png
Type: image/png
Size: 103732 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/daip/attachments/20200622/b97cb960/attachment-0006.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SNPLT_GEO_MBD_afterSNEDT.png
Type: image/png
Size: 154566 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/daip/attachments/20200622/b97cb960/attachment-0007.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: POSSM_J0433+05_2_CL5.png
Type: image/png
Size: 459047 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/daip/attachments/20200622/b97cb960/attachment-0008.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: POSSM_J0433+05_2_CL6.png
Type: image/png
Size: 457728 bytes
Desc: not available
URL: <http://listmgr.nrao.edu/pipermail/daip/attachments/20200622/b97cb960/attachment-0009.png>