sband narrow cal values measured 16nov12

Links to SECTIONS:
Why the cals were remeasured.
Measuring the high correlated cal using blank sky and absorber
Measuring the other cals on blank sky relative to the high correlated cal.
Diagnostics

Why the cals were remeasured.

Measuring the high correlated cal using sky and absorber: (top)

• absorber measurement: morning of 16nov12
  
• on Sky measurements:
  
• 19nov12 9:45 am 
  
• clear sky, no clouds.
  

    The temperatures used in the computation were:
 

Tabsorber	300.6K (81.3F avg temp sensor)
Tsky	5.2K
Treceiver	7K (from ganesh..hilltop)
Tscattered	11 K

    The recording and processing steps were:

• A 172 MHz band centered at 2380 was taken. This used a single mock box.
  
• The 25 Hz hardware winking cal was used.
  
• Spectra were sampled at 2 milliseconds
• Each 20 millisecond calOn,Caloff block was averaged (throwing out spectra before after each cal transition)
• The median in each channel (over the 120 seconds) was used as the average value for calDeflection/Tsys
  
• A robust fit (5th  order harmonic, 1st order polynomial) was done to the calDeflection/Tsys  ratio (1024 points). For the sky fits, 4 points about each excluded point were also removed.

    The results of the reduction are:

• Fits to the Average CalDeflection/Tsys  and HcorCal in Kelvins(.ps)  (.pdf):  This shows the average Tcal/Tsys data with the fits over plotted in red. There is now a large amount of rfi below 2335 and above 2410 MHz. Data outside of this range was not included in the fit (weighted to 0).
  
• Page 1: Tcal/Tsys plots
  
• The top two plots are on the absorber (polA,polB)
• The bottom two plots are on the sky.
• The units are Tsys (about 30K for sky and 300 K for absorber).
  
• The fitRms is computed for the fraction of the spectra used in fitting. The rms and fraction of spectrum used are printed on each plot.
  
• The radiometer equation should give: rms=sqrt(2ratio)./sqrt(172bw/1024chan*120secs)=.0003
• The abs plots are close to this, the sky plots are about 5 times larger.
• Page 2: The Hcorcal in kelvins
  
• The first two plots show the cal fits in kelvins measured from the Sky, absorber, and the sky, absorber ratio (Y factor). The top plot is polA, the middle plot is polB. The dashed line is the receiver temperature used for calSky.
• Tscattered was adjusted to make the sky and absorber measurements match close to 2380 MHz.
• Trcvr was taken as a constant value over the entire band. That's all the info i got from ganesh.
• There is more ripple in the sky measurement than the absorber measurement.
  
• The bottom plot is the cal In kelvins from the Y factor.
•  The * are spaced every 5 MHz. PolA is black and polB is red.
  

Measuring the other cals using sky and the high correlated cal (top)

• hcorcal(on,off)
• hcorcal(on,off),hcorcal(on,off),hcorcal(on,off)
• hcorcal(on,off)
• lcorcal(on,off),lcorcal(on,off),lcorcal(on,off),lcorcal(on,off)
• hcorcal(on,off)

• Each 10 second set was processed similar to the hcorcal above.
• The ratio (calDifX/caloffX was computed (X is each cal type) for each 10 second set and then a robust fit was done (same as hcorcal above).
  
• For each of the "other cals" (hcal,hxcal,h90cal,lcal,lcorcal,lxcal,l90cal)" the ratio (calDifX/calOffX)/(HcorCal) was computed (for sbn these "other cals" were just repetions of hcorcal,lcorcal). The hcorcal value used was interpolated (in time) from the 3 sets of hcorcal measured
  
• The hcorCalFit in kelvins from the hcorcal measurements (see above) was then multiplied into the other cal fit to give each caltype  in Kelvins.
  

    The results of the reduction are:

• Othercals/Hcorcal and the fits (.ps)  (.pdf):
• These plots show the ratio of the other/hcorcal data and the fits to this ratio.
  
• Page 1: Since all the high cals are hcorcal, this just gives unity
  
• page 2: lcorcal. This measurement was repeated 4 times.
  
• top frame polA,bottom from polB
  
• Over plotting all of the cals (in deg K) (.ps) (.pdf). 
  
• Top frame has the high  cals, the bottom framse has the low cals
• The black line showspolA, the red lines show polB.
• the green line is the average of the multiple measurements. This was used for the cal values.
  
• the + on the black plot on the upper frame show the 5 MHz samples used for the cal lookup table.
• the ripple varies some in the lcorcal. You don't see it as much in the hcorcal, but that is probably because the vertical scale of the lowcorcal is blownup.
  

Diagnostics:

• Plotting Tsys measurements 2012 comparing old and new receivers. (.ps) (.pdf):
• The plots show the tsys measurements jan12 -> 21nov12. This data is measured at 2380 MHZ (with the 260 MHz IF).
  
• Pol A is black, polB is red.
• the dashed blue line is when the receiver was installed,
  
• The top frame shows all the data.
• The bottom frame is a blowup of the new receiver.
• It looks like things were bouncing around a little for the first few days of the new sbn.
• Comparing old, new Tsys values:
• Tsys polA has dropped about 1k
• Tsys polB has dropped about 4 or 5 K.
• Part of the new variation may be that the galaxy is overhead during some of these measurements.
• The new horn has a cooled omt. this should decrease the temperature
• the new horn has a wider illumination pattern of the tertiary (to increase the gain). So this should increase the temp.

Summary

• The new cal values were measured on 16,19 nov12
  
• The cal values were installed on 20nov12
  
• the cal values were back dated to be valid from 28oct12 (the installation of the receiver)
  

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