cband cal values measured 28apr16
Links to PLOTS:
to the Average CalDeflection/Tsys and Hcorcal in Kelvins
(.ps) (.pdf): .
OtherCals/Hcorcal and the fits (.ps)
Over plotting all of the cals (in deg
K) (.ps) (.pdf).
Over plotting the new and old
cal values (.ps) (.pdf).
measurements using 28apr16 and jun12 cals (.ps) (.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 cb cal values were measured on 28apr16 using
absorber and sky. The previous measurement was on done on 28jun12.
- The cals had not been measured for 4 years.
- The receiver had been brought down to the lab to be worked on
a few times during these 4 years..
Measuring the high correlated
cal using sky and absorber: (top)
The high correlated cal value (diode 1
going to polA and polB) for cband wide was measured on 28apr16
using the mock
These observations used the mock spectrometer with the
hardware winking cal..
- absorber and sky measurement: morning of 28apr16
The temperatures used in the computation were:
||303.K (85.8)F avg temp sensor)
||from ant test range jun05.
The recording and processing steps were:
- the band from 3900 to 6150 MHz was covered in 3
- Set 1: 3950 to 4800 MHz
- Set 2: 4800 to 5700
- Set 3: 5600 to 6150 (only 4 mock boxes used).
- The mock boxes used 172 MHz bw. sets 1,2 used 7 boxes, set 3
used 4 boxes.
- 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
- The 3950 to 6150 MHz data was
resampled to a fixed spacing of (172/1024=.168KHz). This was
needed since the spectra were overlapped.
- A robust fit (35th order harmonic, 1st order polynomial) was
done to the calDeflection/Tsys ratio (13000+ points). For
the sky fits, 4 points about each excluded point were also
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.
- 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
- 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:
- The abs plots are 2 times this, the sky plots are about 10
- there is lots of rfi about 5100 Mhz .
- 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.
- The Tsys from the sky alone is a little high.
- This may be that the Treceiver curve may be a little
off or Tsky or Tscattered may be off.
- Comparing Tsys from sky alone 28jun12,
28apr16... polB tsys from sky alone has increased more
- This could be Trcvr of polB changing, or
- data taken at different azimuth angles for the two
- there is extra ground radiation getting through
the panels in the long panel direction (more
- The bottom plot is the cal In kelvins from the Y factor.
- PolB has more ripple than polA
- The * are spaced every 25 MHz. PolA is black and
polB is red.
Measuring the other cals using
sky and the high correlated cal (top)
The high correlated cal was measured (see above)
using sky and absorber as the cold and hot load . The other
cals were then measured relative to the high correlated cal on
28apr16 (the times were right after the hcorcal measurements). The
setup was the same as the hcorcal (see above) except that each
integration only lasted for 10 seconds (on sky). The following cal
sequence was run:
The 3950 to 6150 span was measured in 3 sections
(as above). The 25 hz hardware winking cal was used. 10 scans of 10
seconds each covered all the combinations..
the recording and processing steps
- 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
- For each of the "other cals"
(hcal,hxcal,h90cal,lcal,lcorcal,lxcal,l90cal)" the ratio
(calDifX/calOffX)/(HcorCal) was computed. The hcorcal value used
was interpolated (in time) from the 3 sets of hcorcal measured.
Each cal type measurement was re sampled to a fixed frequency
grid covering 3975 to 6075 Mhz.
- The hcorCalFit in kelvins from the hcorcal measurements (see
above) was then multiplied int the other cal fit to give each
caltype in Kelvins.
- Compared with 2012, there is lots of rfi above 5100 Mhz.
The results of the reduction are:
- OtherCals/Hcorcal and the fits
- These plots show the ratio of the otherCal/hcorcal data and
the fits to this ratio.
- Page 1: high cals
- page 2: low cals
- 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 frames has the
- The solid lines show polA, the dashed lines show polB.
- The colors show the different cal types.l
- the + on the black plot on the upper frame show the 25 MHz
samples used for the cal lookup table.
- Over plotting the
new and old cal values (.ps) (.pdf)..
- The solid lines are the new cals. The dash lines are the old
- Top HiCalsPolA: black Diode1 -> polA, Red
- 2nd HiCalsPolB: black Diode1->polB, Red diode2->polB
- 3rd LoCalsPolA: black Diode1 -> polA, Red
- 4th LoCalsPolB: black Diode1->polB, Red diode2->polB
- The old and new cal values are pretty close to one another:
- There are stretches of freq above 5100 that could not be
used for the fit because of the rfi. this
allowed the fit to deviate in these regions (but i guess
people aren't going to be able to observe there either).
- Comparing Tsys
measurements using 28apr16 and jun12 cals (.ps)
- The plots show the tsys measurements jan16 -> jul16. This
data is measured at 5000 MHz.
- Tsys is plotted using the old cal values (polA, polB) and
then replotted using the new cal values (polA, polB)
- A horizontal dashed lines shows 30K
- Top Frame: hcal (diode1 -> polA, diode2->polB)
- 2nd frame: hcorcal (diode 1->polA, diode1 ->polB)
- the gap with no data.. daynumber 50 -> 110 was during the
- Tsys using the new and old cal values is about the same.
- Bottom frame (TsysPolA - TsysPolB)
- Black is Tsys for the old cals, red is tsys for the
- The new cal values do not change the system temperature very
- The new cal values were measured on 28apr16.
- the new cal values came out very close to the old cal values.
- rfi above 5100 Mhz has increased a lot since jun12. the fits
to the measured cal values are not as accurate as they were
before because of this.
- The cal values were installed on 27jul16
- Tsys from Sky alone is normally higher than tsys from absorber
or sky,absorber ratio (probably wrong values for tscattered?).
- But Tsys sky alone polB has moved higher than it was back in
- the cal values were back dated to be valid from 28apr16 (the
date of the measurement).