12meter sband cal values measured 07jun22


Links to PLOTS:

Links to SECTIONS:
Why the cals were remeasured.
The model used to compute the cal values
The parameter values used in the computation
Taking the data
Processing the data
Total power vs time by freq band.
     calRatio (caldif/caloff) vs freq
     Fitting to calRatio vs freq
     Computed Tcal and  tsys vs freq

Why the cals were remeasured.

    The sband cal diode was installed on 220408. On 220606 the diode was moved to the peltier cooler. On 220607 attenuators were installed at the output of the peltier cool (3,2)db in pol(A,B) .. We were supposed to install 7db pads in front of polA,B but the xb,sb pads got reversed.

Parameters used for Tcal computation

    The values i ended up using for the computations (see below for explanations) were:

value Notes
Tabsorber 310K The tabs was 89.5F when we started the xband abs. For the last xb abs measurement, the sun hit the absorber. The 3 sband abs measurements were done and then we measured the abs temp to be 99F.  I ended up used 99F (310K)
Tsky 15K includes any scattered energy. see below
Treceiver 60,65K
 polA,B  see below
omt temperature.. a guess.
reflection coef for horn/omt see below
omt absorption (polA,B)

 Taking the data:

Processing the data:

    For each scan the following is done:

The Results

Total power vs time by freq band

    Plotting the calOn,calOff  total power vs time (.pdf)

Calratio (calDif/calOff) vs frequency

    The 2nd set of plots shows the calRatio vs freq plotted for each scan (.pdf)

Fitting a curve to the calRatios.

   A harmonic fit was  done  to the calRatio vs freq and then the fit was used to compute TCal.

The plots show a fit to the CalRatio measurements (.pdf)

Computed Tcal and Tsys using the cal values.

    The  plots show the computed Tcal and tsys in deg K using the new cal values (.pdf)


processing: x101/220607/measure_cal.pro

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