2014 October 31 VEGAS testing
Overview
At L band, the baseline of the YY polarization was seen to be non-flat by Adam last week.
We will test whether placing some absorber material on the feed removes this wobble.
Method
Data in
TGBT14A _912_43, using Astrid script
TGBT14A_912/Lband_lbw_modes, frequency switching
- Scan 41 - Mode 12; WITH ABSORBER; noticed very high tsys, so restarted for the next scan
- Scan 42 - Mode 12; WITH ABSORBER; still high Tsys but seems unavoidable, so plow on
- Scan 43 - Mode 13; WITH ABSORBER
- Scan 44 - Mode 11; WITH ABSORBER
All the above scans showed high Tsys, and both XX and YY baselines are not flat
At lunch, the absorber material was removed.
Data in
TGBT14A _912_43, using Astrid script
TGBT14A_912/Lband_lbw_modes, frequency switching
- Scan 69 - Mode 12; WITHOUT ABSORBER; Tsys returned to expected levels
- Scan 70 - Mode 13; WITHOUT ABSORBER
- Scan 71 - Model 11; WITHOUT ABSORBER
In the above scans, Tsys was returned to a normal level, however the YY polarization was seen to
show a non-flat baseline, consistent with Adam's previous observations.
Results
Screen grab of getfs output for plnum=0,1 wtih absorber:
Screen grab of getfs output for plnum=0,1 without absorber:
It seems like the absorbing material is not going to be helpful for this purpose.
Further tests are suggested, instead moving the subreflector in and out of focus
to see if this removes the possible standing wave in the system.