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<font face="Helvetica, Arial, sans-serif">The setup scans use the
same source as the first ref ptg scan, so this scan would be
affected. No?<br>
<br>
Heidi<br>
</font><br>
<div class="moz-cite-prefix">On 09/12/2018 11:07 AM, Bryan Butler
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:14411f7e-a4d3-7b52-7353-97c888842590@nrao.edu">
<br>
Please note that not every observation utilizing referenced
pointing is affected by this bug. As I understand it, it only
affects observations where a reference pointing scan immediately
follows a scan on the same source. Most observers do not set up
their SBs in that way, aside from the possibility of the very
first source, so should be immune from this.
<br>
<br>
-Bryan
<br>
<br>
<br>
Rick Perley wrote on 9/12/18 10:01:
<br>
<blockquote type="cite"> As part of the antenna optics
alignment project, my summer student (Lucas Wilkins) and I
discovered an important failure mode in referenced pointing.
The details of this are contained in various emails posts
distributed last May, and will not be repeated here. Due to
the site power issues, it was not possible to diagnose/correct
this problem over the summer.
<br>
<br>
with power now restored, and the array now functional,
Barry suggested, and Ken implemented, a 'quick fix' to this
problem, which was tested yesterday. Ken re-ran a Ku-band
script used last May, both in the original mode, and with the
'fix' put in.
<br>
<br>
The results are very clear:
<br>
<br>
a) The original script showed the failure mode on every
antenna, for every solution. Resulting solutions (in azimuth)
are erratic, and in error.
<br>
<br>
b) The 'fixed' script showed no failures, and the solutions
are consistent throughout the six referenced pointing solutions
made.
<br>
<br>
Barry tells me that the next step is to devise and test a
more elegant solution to the problem, as the current fix is
something of a kludge. I note that the 'quick fix' solution
adds ten seconds to every referenced pointing operation. (The
added 10 seconds is a separate scan, with the antennas on
source).
<br>
<br>
Until this is done, and the final solution tested and
implemented, I strongly urge no observing be done utilizing
referenced pointing.
<br>
<br>
Rick
<br>
<br>
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