Gain-Elevation and Atmospheric Optical Depth Corrections

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8.3.4.3 Gain-Elevation and Atmospheric Optical Depth Corrections

At higher frequencies, it is important to make corrections for atmospheric opacity and gain-elevation effects. NOTE: Currently, the MS to scantable conversion does not adequately populate the azimuth and elevation in the scantable. As a result, one must calculate these via:

  scans.recalc_azel()
  Computed azimuth/elevation using
  Position: [882590, -4.92487e+06, 3.94373e+06]
   Time: 01:48:38 Direction: 05:35:13.5 -05.24.08.2
     => azel: 154.696 43.1847 (deg)
   Time: 01:48:38 Direction: 05:35:13.5 -05.24.08.2
     => azel: 154.696 43.1847 (deg)
   Time: 01:48:38 Direction: 05:35:13.5 -05.24.08.2
     => azel: 154.696 43.1847 (deg)
   Time: 01:48:38 Direction: 05:35:13.5 -05.24.08.2
     => azel: 154.696 43.1847 (deg)
   Time: 01:48:38 Direction: 05:35:13.5 -05.24.08.2
     => azel: 154.696 43.1847 (deg)
   ...

With the correct Az/El, it can be corrected for a known opacity by:

scans.opacity(tau=0.09) # Opacity from which the correction factor:
# exp(tau*zenith-distance)

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