[evlatests] Solar Tests -- round 1

[Rick Perley]

    Ken convinced the system to permit solar observing last week (he can 
supply details on this), so some test data were taken at L, S, and C 
bands.  In this test the 20 dB solar attenuators in the LSC converter 
were not turned on.  We observed a pair of basic calibrators, Cyg A, and 
the sun.  The goal was a simple one -- does the T304 have enough 
attenuation to get the power when observing on the sun down to 
acceptable levels without saturating the system, and are stable fringes 
seen? 

    The answers are 'yes', and 'yes'. 

    1) For all three bands, the T304 had enough attenuation to 'dial 
down' the sun to acceptable levels. 
    2) Strong stable fringes are seen on short baselines at all three bands.

    However, as expected, there is no measureable switched power -- the 
'heat' from the sun is so high that the regular cals are simply buried.  
So no calibration of the fringes is possible.  For this we'll need the 
solar cals to be applied. 

    I note that on some antennas, the apparent Tsys has a negative 
offset -- caused by a small negative offset in the switched power when 
we are observing on the sun.  Might this be due to some non-linearity?