Polarized Tsys using the sbh receiver

run the correlator with 25 Mhz bandwidth, at 3200,3400,3600, and 3800 Mhz, sampling at 1 second intervals.

drive the telescope in az at .2 deg/sec (half slew) from az 270 to 630. Do this at za=2,4.5,7,9.5, and 12 deg (reversing direction on each swing).

Fire the cal 3 times during the measurements to convert to kelvins.

For each az swing compute TsysPola- TsysPolB.

For each az swing fit yfit(az)=c0 +c1*az + c2*cos(az)+c3*sin(az) + c4*cos(2az)+c5*sin(2az). Use the routine corblauto() for the fitting. This routine iterates the fit throwing out points greater than 3 sigma.

The data was taken 11:45 to 14:20 hours so there is interference from the sun as well as continuum sources.

• Fig 1. (TsysA-TsysB) - median(TsysA-TsysB) is plotted vs azimuth for each swing. Each za strip is coded by color. The four boxes correspond to the frequencies 3200,3400,3600, and 3800 Mhz. The large drop at az of 200 degrees is caused by the sun.
• Fig 2-5  show the 2az fit to the data for frequencies 3200,3400,3600, and 3800 Mhz. The black lines are: (data(az)-(c0+c1*az+c2*cos(az)+c3*sin(az))/ The red lines are the 2az fit. The green * are the points that were not used in the fit.   Each figure shows the five az swings at za 2,4.5,7,9.5, and 12 degrees.
• Fig 6. This plots the amplitude and phase of the 2az fit versus za for each frequency. The phase phi (lower plot) is defined as : y=Amp*sin(2*az-phi). When az=phi/2 then the amplitude of the sine wave is 0.

Conclusions:

1. sbh has a .2  Kelvin polarized component to Tsys. This compares to a .5 Kelvin value at 5 Ghz and .2 to .3 K at lbw. These values depend on the accuracy of the cals.
2. The phase is decreasing with za. The phase angle can not be compared directly with the cband and lband measurements since the angles of probes relative to the ground/sky is different for each receiver (although out polarization calibration should measure this using a well known polarized source).

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