xband cal values measured 06jun03
Links to PLOTS:
value versus freq from sky and absorber
of hcorcal on/off-1 on sky
levels during hcorcal measurements
of other cals to hcorcal tracking blank sky.
old and new xband cal values.
Links to SECTIONS:
Measuring the high correlated
cal using blank sky and absorber
Measuring the other cals on blank
sky relative to the high correlated cal.
The high correlated cal value (diode 1 going to
polA and polB) for xband wide was measured 06jun03 on the telescope using
technique. The telescope tracked blank sky and used 3 second
the high correlated cal using sky and absorber: (top)
The cals values had also been measured at the receiver
test shack in dec01. These measurements included the measurement of Treceiver
across the band. The Treceiver measured was used in the 06jun03 reduction.
The temperatures used in the computation were:
||from test shack
Each frequency band was measured 6 separate times on the absorber and
6 separate times on the sky. For each measurement the calon/off-1 spectrum
was computed. A 5th order polynomial was fit to this
data to generate the cal values (throwing out any datapoints greater than
2sigma on the first iteration of the fit). The calValue
versus frequency plots show the results.
of calOn/Caloff-1 for the 6 sky measurements shows the spectra
for the on sky measurements. 100 Mhz junks at a time were taken.
Fig 1 is the measured cal value in deg K versus frequency. The colors are:
Blue is measured using the sky and absorber ratio. Black is using just
the absorber and red is using just the sky. The Top plot is polA and the
bottom plot is polB. The dashed blue line is the cal value measured
at the antenna test range.. The dash green line is the receiver temperature
used (from the antenna test range measurement). The cal value from the
sky agrees pretty well with the values from the absorber and absorber,
sky ratio. This means that the Trcvr, Tsky,Trcvr combination is correct.
Fig 2 is a 5th order polynomial fit to the calAbsorber and calRatio measured
values (it will be used to generate the cal value table). The green crosses
were used for the fit. The dashed blue line is the cal values measured
on the antenna test range.
Fig 3 and 4 show the cal values for each measurement (polA, polB). The
top plot has the 6 measurements on the absorber. The center plot shows
the 6 measurements on the sky. The bottom plot is the absorber, sky ratio.
There are some jumps in the datataking (eg 8750) These jumps repeat in
the sky and absorber measurement (which were separated in time by about
20 minutes) so it is not interference or instabilities in the system.
There are ripples in the spectra. At the high end the
period is about 80 Mhz. This would be a cable length of 150/80. *.6
= 1.1 meters.
Fig 1. This has the entire 2 Ghz. Top is polA, bottom is polB. Each
pass through the frequency range is offset from the previous one for plotting
Fig 2-5 has the same data broken up into 500 Mhz sections.
The final plot
has the power levels during the measurements.
Fig 1 top is the power at the upstairs fiber optic transmitter for all
of the measurements. There were 120*6= 720 records on the sky, and
then 720 records on the absorber. The edges of each 120 records (high at
low freq:8000 and low at 10Ghz) have a higher spectral density since we
are looking at total power and the 1 Ghz IF bandwidth is getting cut off
at the edges of the rf band. So the spectral density for the -37 total
power was probably ok.
Fig 1 center is the power at the downstairs if power meter.
Fig 2 The power counters were not working on the correlator so no data
Fig 3 plots the 25 Mhz 9 level total power measured via the 0 lag of the
correlator. A 25 MHz digital filter sits between the power counter of figure
2 and this measurement.
The high correlated cal was measured above using sky
and absorber as the hot and cold load. On 18jul03 the other cals were measured
relative to the high correlated cal. This went from 8:15 to about
10:30 am. Three passes were done through the frequency range. The
first two passes went from a za of 10 deg rising to 11 degrees setting
tracking blank sky. The 3rd pass started at 10 degree rising tracking the
same declination but a different ra. The sky was clear the entire time.
The cal sequence was:
Measuring the other
cals using sky and the high correlated cal from above. (top)
100 Mhz at a time was measured (4 by 25Mhz) going from
8000 to 10000 Mhz. The cal was cycled on/off for 3 secs at each step.
The entire frequency range was repeated 3 times.
The calOn/calOff -1 spectra was computed for
each measurement (giving cal in units of calOff or Tsys). Each of
these 25 Mhz band passes was cumfiltered. This was done on the 3 loops
of the same freq band (256 channels *2 numbers). The total power was computed
and then the ratio of each cal value relative to the hcorcal was computed
(via interpolation of the 3 hcorcal measurements). These values were used
to generate the cals table (after multiplying by the hcorcal in kelvins).
An 11 order polynomial fit to the data was done for display purposes
(but it was not used to generate the cal values). The figures
show the other cals relative to Tsys and the hcorcal:
The final plot shows how
the measured cal values have changed.
Fig 1. This is the cal value as a fraction of Tsys for each of the cal
types. The top figure has the high cals while the bottom figure shows the
low cals. The lines with * are polB. The cal types where the same diode
feeds the same polarization (polA horcal,hcal.. polB hxcal,hcorcal, etc)
are in agreement. Since they were measured at different times, the weather
was not having large affect on the data.
Fig 2. The calType/hcorcal. The top has the high cals while the lower plot
is the low cals. The vertical dotted lines show the boundaries for each
100 Mhz measurement. There is a bump in the cal values starting at 9300
Mhz. The * are an 11th order fit to the data. The higher frequency
components of the data are not random (they are correlated between different
measurements). Because of this, I used the data rather than the fits to
generate the cal values.
Fig 3. The hcorcal was measured 3 times in each set of 10 measurements.
This graph plots the ratio of tsys for the 2ndHcorcal/1stHcorcal (red)
and 3rdHcorcal/1stHcorcal (blue). The * have the cal on while the + have
the cal off. Each frame is a different pass through the frequency range.
These are the raw tsys values. There has been no cumfiltering done yet.
If the + and * jump together, then it was Tsys that was changing. If the
+ and * jump differently then it could have been the cal value. The ratios
have interpolated between the 3 hcorcal measurements. Most jumps are within
The solid lines are the current measurements. The dashed lines were taken
with the receiver on the hilltop test range. The calval values are
a bit lower (this decreased Tsys and the gain). The largest difference
is polA below 8500 Mhz.