[evlatests] 'Missing' panels on ea21

[rperley]

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.

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.

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.

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.

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'.

Rick