[evlatests] Pointing, and Q-band sensitivities

[Rick Perley]

    It was noted previously that 4 EVLA antennas showed poor sensitivity 
at Q-band, while one (13) was normal.  It was speculated this result 
reflected a failure in referenced pointing. 

    I have obtained the pointing solutions, and the speculation is 
correct.  Four EVLA antennas failed their referenced solutions, and one 
was successful -- antenna 13. 

    All antennas found solutions at K-band.  It thus appears that 
secondary referenced pointing is required at Q-band only, while for 
K-band, observers can use primary referenced pointing with a high 
probability of success.

    It is interesting to note that the failure of Q-band primary 
pointing is not due to errors in collimation, or in the primary pointing 
parameters.  The solutions found at K-band show that ALL antennas had an 
elevation error typically 0.4 arcminutes -- all of the same sign -- 
reflecting a poor refraction model.  (Is this error expected?)  The 
source elevation at the time was 41 degrees, and the data were taken 
about midnight in calm, dry weather.