Pages 1-2: total power vs time. No polynomial removed.
black is polA, red is polB.
Each frame is a separate frequency band.
The vertical lines mark every 600 seconds (to help align things
in adjacent bands).
total total power varies 0 to 2% of tsys
Pages 3-4: total power vs time with 2nd order polynomial removed.
Same as pages 1-2 but the 2nd order polynomial was removed.
This allows us to blow up the vertical scale.
Page 5: Spectra of the total power.
the spectra of the total power was computed for the first 3600
seconds.
Top frame: polA, bottom frame polB. Each colored plot is a
totalPower spectra from a different frequency band.
The black (4325 band) has a set of harmonics with .13 Hz
(7.69sec period). This may be coming from rfi leaking in.
DISCUSSION:
The total power varies by up to 2% of Tsys over the 6478 seconds.
Tsys is probably 300 Kelvins with the shutter closed.
The variation includes the receiver and the iflo.
Some of the spikes in the total power spectrum may come from rfi
leaking through the shutter. There is occasional strong rfi in the 4325
band.
Comparing this variation with that seen on the sky.
Tsys on the sky is about 30K. Tsys on the shutter is probably
around 300K.
If there is a gain variation, then having Tsysshould not make
any difference.
If variations are "extra noise power" added near the frontend,
then the Tsys difference may make a difference.
The dome did not move during the test.
If there is a loose connection in the dome, then
tracking a source may cause the gain through this connection to
vary more than when the dome sits still.