Xband gain curves elevation rail shimming to new horn.

Mar 2003

Links to the plots:
The cal jump around jul03
The mar03-jul03 gain curve fits vs az,za
The jul03-sept03 gain curve fits vs za

    The elevation rails were shimmed and the dome position was changed in feb 03. Calibration runs from mar03 thru sep03 were used to compute  new gain curves (the new xband horn was installed in oct03). The cal box was taken down to the lab sometime in jul03. When it was reinstalled, the system temperatures jumped (probably because the cal values changed). Because of this, the gain curves were split into two sections: Mar03 to 19jul03 and 20jul03 thru sep04.
    The data was taken at 8500, 8800, 9000, and 9200 Mhz.  For the period mar03 to jul03 the gain curves were fit as a function of azimuth and zenith angle.  For jul03 thru sep03 the fit  only included the za dependence (since there were not enough tracks to constrain the azimuth terms). The fitting function (with az,za in degrees) is:

g(az,za)=c0 +c1*(za-10) + c2*(za-10)^2 +c3*(za-10)^3 +
                  c4*cos(az) + c5*sin(az) + c6*cos(2az) + c7*sin(2az) + c8*cos(3az)+c9*sin(3az)

The  plots:
Mar03-jul03 gain fits vs az, za with the fit residuals.
20jul03-sept03 gain fits vs za with the fit residuals.

Summary of gain fits
each Freq
fitrms (K/Jy)

       The data is fit to (polA+polB)/2. The cal values for the two polarization's  give system temperatures that differ by up to 10 Kelvins (45K vs 55K). If you apply the gain curve to a single polarization using its cal value, then the gain may be off . If you compute the gain on both polarization's and then average the values, you will have duplicated what the fitting routines have done. This method will give a better "transfer" of flux from the calibrators used in the fitting to the sources that you are measuring.

     The idl routines gainget() or corhgainget() will now return the xband gain for data taken mar03 thru sep03 using these fits. The coefficients can be found in the ascii file  data/gain.datR11 (this is provided in the AO idl distribution for correlator routines). You can also find a copy of it at AO in /home/phil/idl/data/gain.datR11.

processing: x101/xb/gain/mar03/dogainfit.pro