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: http://www.naic.edu/~phil/xband/gainMar03/gainCurvesMar03.html
Дата изменения: Sat Mar 27 21:56:05 2004 Дата индексирования: Sat Dec 22 20:04:17 2007 Кодировка: Поисковые слова: m 63 |
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.
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each Freq |
fitrms (K/Jy) |
fitrms(K/Jy) |
fitrms(K/Jy) |
fitrms(K/Jy) |
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NOTE:
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.prohome_~phil