A2488: dps with 800 Mhz rcvr
may08
Intro:
A2488 is using double position switching on sources
using the 800 Mhz receiver. The mock spectrometer is used to record the
data. The setup is:
- 5Mhz, 8Mhz, and 172 Mhz bands taken. Each with 8192 channels.
- 1 second dumps
- 240 seconds on and off source and calibrator.
Compare polA with polB (10aug09)
The observers reported that the rms for polB is
about 70% larger than the rms for polB. This is measured across the dps
spectra result.
The dps processing is:
- Compute onoffSrc=OnSrc-offSrc
- compute onoffBpc = onBpc - offBpc (bpc = bandpass
calibrator)
- dpsSpectra= onoffSrc/onoffBpc
The processing leaves the dps spectra in units of the bandpass
calibrator source strength.
Plots were made of the average spectral
density and rms value for 35 dps spectra (.ps) (.pdf):
- Page 1 vs dps scan number
- top: mean spectra value vs dps scan number. black is pola, red
is polB.
- Two separate sources/calibrators were looked at.
- there is an oscillation in the dps mean value.
- bottom: Rms value across each spectra vs dps scan number
- Rfi has been removed before computing the rms
- polB rms is greater than polA rms except for the 2nd source.
- Page 2: dps mean spectral value vs az,za
- Top: mean dps spectra value vs azimuth:
- there is a clear 180 deg period implying polarized power
coming in from somewhere.
- bottom: Mean dps spectral value vs za.
SUMMARY:
- The rms for polB is larger than the rms for polA
- There is polarized power in the average dps spectra. The
amplitude is about 10%. the source is around 1631+11. This is in the
top part of the north polar spur which has polarized power (although
you might expect the calibration to remove this).
processing: usrproj/a2488/10aug09.pro
home_~phil