Polarized Tsys using the sbh receiver

may 2003

     Polarized components of Tsys have been previously measured with the lbw and cband receivers.  On 16may03 measurements of tsys were done using sbh (3 to 4 Ghz linear feed) to see how the component changed with frequency.
    The setup and processing was:
  • 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.
  •     The plots show the difference  TsysA-TsysB vs az and za for this dataset:


    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).
    processing: x101/030516/sbhswing/poldif.pro