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<font face="monospace">Hi Rick-<br>
<br>
Your query reminds me of the panel that detached from *ea20* (not
ea21) back on a windy Oct 28, 2019, during the move into
D-array. One wonders if you see a similar drop-out in the
holography before (or even after) the repair, which was within a
week or so, I think. </font><font face="monospace"><font
face="monospace">(See photo below; I'm not quite sure how to
associate your holography coords with that pic, though that gap
is on the left side looking into the dish from above, if the
antenna is tilted down.)</font><br>
<br>
Ultimately, the diagnosis was some rusty bolts, and one wonders if
there are loose edge panels more generally..... Maybe wind has
dislodged (but not yet detached) a few panels on ea21.... And
maybe a good thing that this isn't more common in your holography
results? (Folks walking on antenna surfaces should maybe be
careful....)<br>
<br>
(NB: Lest there be any confusion, when I initially reported the
detached panel, I mistakenly identified it as ea21 (the one you
are describing today!) on pad N01, which I thought was the first
north arm pad visible from the webcam; rather, N01 is behind the
whole line of west arm pads from that perspective. The detached
panel was ea20 on N02, in fact. I think we have speculated
previously, but inconclusively(?), on whether or not the possibly
tenuous state of that panel would have been evident in holography
around that time....)<br>
<br>
Cheers,<br>
George<br>
<br>
<br>
<img src="cid:part1.BFE0B05E.9F926431@nrao.edu" alt="" width="960"
height="539"><br>
<br>
<br>
</font><br>
<div class="moz-cite-prefix">On 5/19/21 3:01 PM, rperley via
evlatests wrote:<br>
</div>
<blockquote type="cite"
cite="mid:96aad03b24c80a0b7fa812de6945a980@nrao.edu">I'm reviewing
all the surface holography taken over the past three years. The
good news is that there is ample evidence that the panels don't
change over this period of time, so that once we've made our
'best' adjustments, no more adjustments will be needed for a long
time.
<br>
<br>
The 'bad' news is that something is quite amiss with ea21. We're
getting no signals from two panels - this is seen in both the Jan
2019 and May 2020 data.
<br>
<br>
Of course, these panels cannot be 'gone' (one hopes that somebody
would have noticed this, were that the case ...). What has
happened is that the two panels are tilted so much that we don't
get a coherent signal over the resolution of the measurements.
<br>
<br>
The two panels are in the outermost right, and, as seen from the
front, looking into the dish, are the top two panels on the right
side of the quad leg.
<br>
<br>
It would be useful for somebody to look at these -- the effect
will be very slight, so don't expect an obvious tilt. It takes
only a couple of millimeters of slope, over the extent of the
panel, to make it 'disappear'.
<br>
<br>
Rick
<br>
<br>
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</blockquote>
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