sband narrow cal values measured 16nov12
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 Tsys measurements
2012 comparing old and new receivers. (.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 sbn cal values were measured on 16nov12
(absorber) and 19nov12 (on sky). They cals were remeasured
because a new receiver was installed 28oct12.
Measuring the high correlated
cal using sky and absorber: (top)
The high correlated cal value (diode 1
going to polA and polB) for sbn wide was measured on 16nov1`2
using the mock
These observations used the mock spectrometer with the
hardware winking cal..
- absorber measurement: morning of 16nov12
- on Sky measurements:
- 19nov12 9:45 am
- clear sky, no clouds.
The temperatures used in the computation were:
||300.6K (81.3F avg temp sensor)
||7K (from ganesh..hilltop)
The recording and processing steps were:
- A 172 MHz band centered at 2380 was taken. This used a single
- 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
- A robust fit (5th order harmonic, 1st order polynomial)
was done to the calDeflection/Tsys ratio (1024 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. There
is now a large amount of rfi below 2335 and above 2410 MHz. Data
outside of this range was not included in the fit (weighted to
- 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 5
- Page 2: The Hcorcal
- 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.
- Tscattered was adjusted to make the sky and absorber
measurements match close to 2380 MHz.
- Trcvr was taken as a constant value over the entire
band. That's all the info i got from ganesh.
- There is more ripple in the sky measurement than the
- The bottom plot is the cal In kelvins from the Y factor.
- The * are spaced every 5 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
19nov12 around 9:45 am. The setup was the same as the hcorcal (see
above) except that each integration only lasted for 10 seconds
(on sky). Most receivers have hcorcal,hcal,hxcal,h90cal and
well as the low cal versions of this. Sbn only has hcorcal and
lcorcal. I repeated the hcorcal or lcorcal measurement so that we
ended up with the same number of measurements. This let the offline
reduction software run without too many changes. Since we had 4
copies of each ratio, i ended up averaging these.
The following cal sequence was run:
. 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 (for sbn these "other
cals" were just repetions of hcorcal,lcorcal). The hcorcal value
used was interpolated (in time) from the 3 sets of hcorcal
- The hcorCalFit in kelvins from the hcorcal measurements (see
above) was then multiplied into the other cal fit to give each
caltype in Kelvins.
The results of the reduction are:
- Othercals/Hcorcal and the
fits (.ps) (.pdf):
- These plots show the ratio of the other/hcorcal data and the
fits to this ratio.
- Page 1: Since all the high cals are hcorcal, this just gives
- page 2: lcorcal. This measurement was repeated 4 times.
- 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 black line showspolA, the red lines show polB.
- the green line is the average of the multiple measurements.
This was used for the cal values.
- the + on the black plot on the upper frame show the 5 MHz
samples used for the cal lookup table.
- the ripple varies some in the lcorcal. You don't see it as
much in the hcorcal, but that is probably because the vertical
scale of the lowcorcal is blownup.
- Plotting Tsys
measurements 2012 comparing old and new receivers. (.ps) (.pdf):
- The plots show the tsys measurements jan12 -> 21nov12.
This data is measured at 2380 MHZ (with the 260 MHz IF).
- Pol A is black, polB is red.
- the dashed blue line is when the receiver was installed,
- The top frame shows all the data.
- The bottom frame is a blowup of the new receiver.
- It looks like things were bouncing around a little for the
first few days of the new sbn.
- Comparing old, new Tsys values:
- Tsys polA has dropped about 1k
- Tsys polB has dropped about 4 or 5 K.
- Part of the new variation may be that the galaxy is
overhead during some of these measurements.
- The new horn has a cooled omt. this should decrease the
- the new horn has a wider illumination pattern of the
tertiary (to increase the gain). So this should increase the
- The new cal values were measured on 16,19 nov12
- The cal values were installed on 20nov12
- the cal values were back dated to be valid from 28oct12 (the
installation of the receiver)