Hurricane Maria hit hit the observatory on 20sep2017. The high winds and water damaged the dish. X102 calibration data taken 07dec17 through jun18 were used to compute new gain curves.  Data was taken with the interim correlator. Since the correlator can only measure 4 frequency bands simultaneously, two different frequency groups were used :(1155,1310,1375,1415) and (1415,1550,1610,1666). These frequencies changed a bit since the last gain curve (because of rfi).  Gain curves were then computed fitting for gain as a function of za (fits using azimuth terms were also made, but the za only fits were used for the official gain curves).  The fitting function (with za in degrees) is:

g(za)=c0 +c1*za + c2*(za-14)^2 +c3*(za-14)^3

The plots show the gain fits vs za with the fit residuals (.ps)   (.pdf)

• Fig 1 shows the az,za distribution for the data. The top plot is the az,za positions for the frequency group (1155,1310,1375,1415) while the bottom plot has the positions for the (1415,1550,1610,1666) group.
• Fig 2-3 are the individual fits for each frequency. The data is in red, the black lines are the fits. The fit values are listed on each plot. The rms of the fit is listed at: (sigma(y-yfit)) for each plot.
• Fig 4-5 are the fit residuals in K/Jy for each frequency.

      1415 MHz has twice the measurements for the fits since it was included in both frequency groups. The 1550 band rms is high because there is rfi in the band.

Note: The fits including  za and az terms (,ps)   (.pdf)  are available for comparison. They are not the curves being used.

Comparing the pre/post maria gain curves.

• The gain curves were evauated for za=2..19 deg za (the curves have no azimuth dependence)
• Page 1: Pre and Post maria gain curves vs za
• he solid lines are the pre maria gain curves.
• the dashed lines are the post maria gain curves.
  
• The top plots has the curves for 1155,1310, and 1375 MHz.
• The bottom plot has the curves for 1415,1550,1610, and 1666 mhz
• Page 2: the ration of PreMariaGain/PostMariaGain
• The top frame has 1155,1310, and 1375
• the bottom frame has 1415, 1550,1610, and 1666
• The gain has decreased by 25 to 30%. the 1550 MHz curve is an outlier.. most likely because of the increased rfi in the band.

Notes:

• The pre maria gain curves fit pretty well without any azimuth dependence included.
• Looking at the post maria curves (for all freq) there is more azimuth dependence.
• the preliminary blackmore survey of the dish showed the southern part of the dish with a radius of curvature larger than the standard value
• the southern part of the dish has historically had a problem with sinking (partial fill area when the dish was constructed), but it looks like hurricane maria may have made it worse.
• I ended up using the same fitting function (no az dependence) for the post maria fits .. this allowed a better comparison between pre,post maria gains...
  

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