Intro:

Setup:

• 7 172 bands covering  4200 to 5200 MHz were used. 172/1024 = 172 kHz resolution was used.
  
• 900 second scans  at .9 second integrations were taken. There were 9 complete scans.
• The mock spectrometer took full stokes data with 32 bit dumps.

Processing:

•  The first N samples were taken as the On position while the next N  samples were the off position.  The offset between the on and the off tracks on the dish where then N*source motion in .9 seconds.
  
• The offsets used (N) were:
• 1,5,10,20,25,50,100 samples corresponding to great circle angular offsets of .004,.02,.04,.07,.09,.18, and .35 degrees.
• Each  trial had 450 seconds on and 450 seconds off.
• Since the same source was tracked, the main beam power should not have changed.
• For each scan:
• compute the on/off for the 7 different offsets.
  
• Do this for each of the 7 frequency bands.
• Compute the baseline rms for each on/off spectra (throwing out outliers).
• Record the   measured/expected rms (from the radiometer equation).
• Record the   acf of on/off to get the power vs delay to see if the 1 usec standing wave is present.

• Page 1: rms vs great circle offset.
  
• Each frame is a different frequency band
• black is polA, green is polB.
• The rms starts to increase at .2 degrees. Part of the spread is from rfi.
• Page 2: rms vs little circle offset.
• These are the same plots as page 1 except they are versus little circle offsets (azdif is not multiplied by  sin(za).)
• The offsets do not group as well as the great circle offsets. This is a little strange since ground based radiation might be more sensitive to little circle offsets than great circle.

•  The 7 different on,off offsets are separated by dashed lines (the bottom has the smallest offsets).
• Within each set, the acfs for the  5 frequencies (4275 and 4405 had rfi), and 9 scans are shown.
• You start to see a vertical line around 1.03 usecs start in the 4th section (.07 degree offsets). It is  strongest at the top section (.35 degrees).
• A second  reflection is seen at .9 usecs in the top section.
• The lower delays (0-.2) start to have power i the 3rd section.

Summary:

• 450 sec on,offs which track different parts of the dish were  constructed from a 900 sec track of a source.
• great circle offsets of .004,.02,.04,.07,.09,.18,.35 degrees were tested.
• The rms of the on/off starts to increase around .2 degrees.
• The rms increase correlates better with great rather than little circle offsets.
• the 1 usec standing wave starts to be seen in the .07 degree offsets.
• a .9 usec standing wave is seen at .35 degrees offset.
• The rms increase is probably also a function of az,za and not just the offset distance. It probably correlates with the telescope symmetry.
• standing wave at cband have the same period as lband. The phase moves 4 times faster as the distance changes. It would be a good idea to repeat this at lband.
  

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