cband cal values measured 28jun12
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 28jun12 and mar04 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 28jun12
(absorber) and 29jun12 (on sky). The previous measurement was
on done on 06jul06.
- The cals had not been measured for 6 years.
- The receiver had been brought down to the lab to be worked on
a few times during these 6 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 28jun12
using the mock
These observations used the mock spectrometer with the
hardware winking cal..
- absorber measurement: morning of 28jun12
- on Sky measurements:
- 29jun12 - 16:00 to 17:30
- Lots of clouds during the sky measurements. This may affect
The temperatures used in the computation were:
||303.7K (87.1F 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 close to this, the sky plots are about
10 times larger.
- Page 2: The Hcorcal
kelvins (.ps) (.pdf).
- 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 hight. This may
be that the Treceiver curve may be a little off.
- 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
29jun12 (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.
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 framse 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:
- The bumps in the cal values for the new data comes from
rfi. This was not as prevalent back in 2006.
- Comparing Tsys
measurements using 28jun12 and dec08 cals (.ps)
- The plots show the tsys measurements jan12 -> 17sep12.
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)
- Currently the new cals have TsysA,B the same value (about
35K). With the old cals they were higher and differed by about
- Bottom frame (TsysPolA - TsysPolB)
- Black is Tsys for the old cals, red is tsys for the
- there was a jump down in the polB tsys value around
18jul12. This was after a receiver warmup,cooldown
- The new cal values do not change the system temperature very
- Stokes Calibration check:
- The stokes calibration processing computes deltaG which is
the error in the the cal Difference (CalPolA -
- Delta G using the old cal values ranged from .5 to 2.3%. The
new cal values did not change this much.
- The new cal values were measured on 28 and 29jun12.
- the new cal values came out very close to the old cal values
(so i guess you can go 6 years without remeasuring the cals!!!).
- The cal values were installed on 17jun12
- the cal values were back dated to be valid from 28jun12 (the
date of the measurement).