lbw gain curves after Hurricane Maria

June 2018

Links to the plots:
The jun18 gain curve fits vs za (new curve) (.ps)  (.pdf)
The jun18 gain curve fit to az and za (just for comparison) (.ps)    (.pdf)
The ratio of postMariaGain/PreMariaGain (.ps)     (.pdf)
 

    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
where the ^2 and ^3 terms are only applied for za ge 14 degrees.
There were a total of 1791 measurements over all frequencies. 7 of these were rejected do to bad measurements.

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

Summary of gain fits
freq # of points fit rms
K/Jy
1155
242
.3
1310
244
.5
1375
225
.3
1415
469
.4
1550
169
1.0
1610
215
.5
1665
210
.5

      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 plots show the pre maria and pos maria gain curves  (.ps) (.pdf):


Notes:



  The idl routines gainget() or corhgainget() will now return the lbw gain for data after 01mar03 using these fits. The coefficients can be found in the ascii file  data/gain.datR5 (this is provided in the AO idl distribution for correlator routines). You can also find a copy of it at http://www.naic.edu/~phil/gaincurves/gain.datR5
processing: x101/lb/jun18/dogainfit.pro
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