[evlatests] One mystery resolved ...

[Rick Perley]

    The mystery of why data from antennas 6 and 16 gave pointing 
solutions, but were absent from the filled data, is now explained.   
It's shadowing!  The observations were taken at an elevation of 12 
degrees, at an azimuth of 58 degrees.  The entire west arm shadowed 
itself. 
    Ken explains that the Modcomps, when solving for pointing, don't 
care about shadowing.  Antennas 6 and 16 are near the end of the West 
arm -- the shadowing was small enough to permit good solutions, but 
large enough (more than zero!) to prevent the data being filled. 
    Antennas 4, 24, and 8, all of which gave no pointing solutions (or 
filled data) are in the inner part of the West arm -- the shadowing was 
apparently sufficient to prevent a solution. 
    I refilled, with the shadowing restrictions removed, and all 
antennas are present .

    It's not obvious to me that the low elevation should cause the low 
sensitivity at K and Q bands, however (by the unshadowed antennas).