Dec07 polB Tsys increases

18dec07: checking the sefd dec07:

       After the painting upgrade (dec07) the Tsys lbw polB increased. This could be a real increase in Tsys or the cals values could have changed (since the dewar was worked on).
    On 18dec07 two calibration scans were done using lbw to verify the pointing model for lbw.

    The plots show the polA,polB results for the calibration runs (.ps) (.pdf):

• Page 1 shows the PolA, polB values.
  
• + is polA, * is polB. The frequencies are color coded. Two sources are included in the data.
• Tsys for polB is higher.
  
• The gains for polA,polB are similar.  (looks like one src is a bit off).
• The sefd for polB is higher than sefd for polA
• Page 2: The ratio polA/polB plotted vs za.
• Frequencies are color coded.
• + is B0949+287, * is J0141+138. Neither of the sources are polarized.
• The Tsys,Tsrc Ratios values for J0141+138 differ from those of B0949+287. This could be the cal values are a bit off.
  
• The ratio SefdA/sefdB is consistent for both sources at about 70-80%. This is independent of the cals.
• The sources are not polarized and hopefully there is not a gigantic beam squint so the data says that Tsys for polA is 75% less than Tsys for polB
• Page 3: plot the ratios vs frequency.
• There may be a trend where the sefdRatio decreases with Frequency implying that TsysPolB gets worse as you increase the frequency.
  

07feb08 SefdPolA/SefdPolB after adjusting the dewar biases.

• Page 1: Tsys,Tsrc,Sefd for polA,polB separately
• TsysPolA is the same as TsysPolB
• TsrcPolA is larger then TsrcPolB.
• There are two measurements near the same za. One for source rising and one for source setting. Tsrc shows a difference in these two measurements. This source is 3.7% polarized so the polarized Tsrc will change with azimuth.
• The sefdA is still lower than sefdB
• Page 2 Ratios vs za
• TsysA/TsysB is close to 1.
• TsrcA is greater than TsrcB and it differs with az.
• SefdA/sefdB is now about 85 to 90% after averaging the two azimuths.

• adjusting the dewar biases increased the SefdA/SefdB ratio from .75 to about .85 or .9.
• the source used was 3.7% polarized at 1415Mhz (nvss). This caused the sefdRatio to vary with az.
  

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