cband cal values measured 10jun05


Links to PLOTS:
     Fits to the Average CalDeflection/Tsys (.pdf)
     Hcorcal in kelvins (.pdf)
           CalDeflection/Tsys for the 9 passes (.pdf)
           Fits to the CalDeflection/Tsys for the 9 passes (.pdf)
       The average calValues in kelvins and the fits (.pdf)
        Over plotting all of the cals (in deg K) (.pdf)
           CalDeflectionCalX/calDeflectionHcorcal for the 3 passes (.pdf)
           CalDeflX/calDeflHcorcal.. fit residuals for each pass (.pdf)
           Plotting tsysall  with the new cal values (.pdf)

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.

Why the cals were remeasured.

     The amplifiers for cband were replaced on 25may05. 
Measuring the high correlated cal using sky and absorber: (top)
    The high correlated  cal value (diode 1 going to polA and polB) for cband was measured 10jun05 (on absorber) and (08jul05 on sky)  using  the sky/absorber technique.  The observations used 3 second calon followed by 3 second cal off. For the sky observations, blank sky was tracked.

    The temperatures used in the computation were:
Tabsorber 301.5 K
Tsky 3 K
Treceiver from rcvr test shack
Tscattered 15 K

    The band 4000 to 6000 MHz was covered 9 times on absorber and sky. The ratio (CalOn-CalOff)/CallOff was then computed for the data. Each spectra of 2000 Mhz (20480 points) was then fit to an 23rd order harmonic and 1st order polynomial (the order was chosen to include the ripples in the caldefl/Tsys spectra). The fit was iterated throwing out points whose residuals were greater than 3 sigma . Whenever a point was excluded, 5 points adjacent to the fit were also excluded . Some regions of some passes were completely excluded because of rfi.

    A robust average of the  passes was then computed (iterating and throwing out outliers). The average spectra was then fit with the same function. See reducing the cal data for more info on the reduction.

    The results of the reduction are:

    The first set of plots show the calOn-caloff/caloff for each pass through the data. The second set over plots the fits to each pass to see how stable the system is.
processing: x101/cb/cals/jun05/hcorcal/,,,

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

    The high correlated cal was measured above using sky and absorber as the hot and cold load. The other cals were then measured relative to the high correlated cal. Blank sky was tracked and the following cal sequence was run:     100 Mhz at a time was measured (4 by 25Mhz) going from 4000 to 6000 Mhz. The cal was cycled on/off for 3 secs at each step.  The entire frequency range was repeated 3 times.
    The ratio (calOnX-calOffX)/caloffX was computed (X is the other cals) and then it was divided by (calOnHcor-calOffHcor)/calOffHcor). A spectrum for the entire pass was then constructed of the other cals relative to the hcorcal. The spectra for the 3 passes were averaged. The average spectra was multiplied by the hcorCal value in kelvins (this removed the hcorCal shape). The resulting spectra was fit with an 23th order harmonic and 1st order polynomial. For more info see computing the cal value.

   The results of the reduction are:

processing: x101/cb/cals/jun05/othercals/,,,