[evlatests] K-band OSRO1 observing, Saturday/Sunday

[Rick Perley]

    A ten-hour run on Cyg A, in OSRO1 mode, was run Saturday 
night/Sunday morning.  As at the low frequencies, I cycled around three 
frequency pairs, in this case, these are in K, Ka, and Q bands. 

    At K-band, three positions were selected, corresponding to the two 
lobes and the center of the source.  The frequencies chosen were 19.0 
and 24.0 GHz (BD and AC, respectively).  Calibration was done on the 
nearby source J2007+4029, and 3C286. 

    In general, the K-band data are very good.  In no case was more than 
15 seconds of flagging required at the beginning of each observation -- 
it seems there are no significant 'setup' issues. 

    FITLD found 3.3% of the data were integer zero -- most of these are 
associated with antenna 6B (see below). 

    The notable issues found are:

    1) Antenna 20 has a period oscillation in its gain -- this is known 
to be a pointing effect, and work is believed underway to correct this.
    2) Antenna 15, IF 'A' had a rather large delay error -- 16 nsec.  
All others were less than 5 nsec.
    3) The Cross-Hand delays are 2.2 nsec in IFpairs AC, and 8.0 nsec in 
IFpairs BD. 
    4) Antenna 13, IF 'B', and antenna 22, IF 'D', gave no fringes 
throughout. 
    5) Antenna 6, IF 'B' also provided no fringes -- in this case, the 
data were all integer zero. 
    6) Antenna 27 was extremely weak in IF 'B; (amplitudes low by factor 
~100), and very weak in IF 'D'. 
    7) Antenna 5, IF 'B' gave integer zero data for the first 1.7 hours, 
then 'sprang to life', and was fine the rest of the way. 
   
    Initial imaging shows fine results, except that, as at the lower 
frequencies, the noise in the Cyg A images is at least 50 times too 
high!  This is likely to be due to errors in calibration, the specifics 
of which elude me.  Images of the nearby point-source calibrator provide 
50,000:1 DR images which appear perfectly noise dominated (noise is 
about 90 microJy, using 120 MHz bandwidth and 1000 seconds of on-source 
integration).  This is high than theoretical, but probably not too far 
off, given the time of year.