xband 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).
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 xb cal values were measured on 28jun12
(absorber) and 01jul12 (on sky). The previous measurement was
on done at the receiver test range on mar04. Some reasons why the
cals were remeasured were:
- The cals had not been measured for 8 years.
- Tsys was higher than expected (38-40 K).
Measuring the high correlated
cal using sky and absorber: (top)
The high correlated cal value (diode 1
going to polA and polB) for xband 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:
- 01jul12 - 11:00 am light clouds.
The temperatures used in the computation were:
||303.7K (87.1F avg temp sensor)
||from test shack mar04
The recording and processing steps were:
- the band from 7900 to 10100 MHz was covered in 3 sections:
- Set 1: 7900 to 8760 MHz
- Note: the last band of the first set was mispositioned in
freq so it was not recorded.
- Set 2: 8715 to 9605
- Set 3: 9555 to 1084 (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 7900 to 10100 MHz data was resampled to
a fixed spacing of (172/1024=.168KHz). This was needed since
the spectra were overlapped.
- A robust fit (28th 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 dropout is the last band of set 1 that was not
- 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.
- The ripple is probably coming from the cal
- 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.
- All 3 of the measurements agree with one another.
- The bottom plot is the cal In kelvins from the Y factor.
- The ripple period is about 180 MHz. It could be a
reflection in air of about .83Meters or .6 meters in
a median with n=1/.7.
- The * are spaced every 25 MHz. PolA is black and
polB is red.The old cal table was spaced by 100 MHz. This
did not sample the cal ripple often enough.
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
01jul12 (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 7900 to 10100 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 7900 to 10100MHz.
- 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 frams 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 10 MHz
samples used for the cal lookup table.
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 cal values measured on the antenna test range did
not see the large ripple in the cals (probably because of
- PolB seems to have changed more than polA.
- Comparing Tsys
measurements using 28jun12 and dec08 cals (.ps)
- The plots show the tsys measurements jan12 -> 09aug12.
This data is measured at 8800 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
- Stokes Calibration check:
- The stokes calibration processing computes deltaG which is
the error in the the cal Difference (CalPolA -
- Calibration data was taken on 04may12 on B0518+165. It was
processed with the old cal values, and then reprocessed with
the new cal values.
- Below shows the change in delta g:
- The new cal values have improved the error in CalA-CalB.
- Ripple across the band.
- There is a large ripple in the CalDeflection/Tsys bandpass.
It as a period of about 180 MHz. This could be a reflection of
about .6 meters if the velocity in the medium is .7 c.