[evlatests] P-band Tcals

[Rick Perley]

I've extended my tests of sky-calibrating Tcal values to P-band, using 3C147 as the 'known' source.  The results, using the A-configuration flux density data taken in January 2025, are very good, in the sense that applying the derived Tcal values gives excellent visibility estimates after TYAPL.

But there are two notable issues:


  1.
Only seven VLA antennas have default Tcal values not equal to 1.0.  (These are currently ea12, 18, 20, 23, 24, 25, and 26, whose receivers are:  4P-06, -29, -18, -25, -05, -08 and -24, respectively).  So either the Tcals on the other receivers were never measured, or the values measured were never implemented.
  2.
The 'sky-calibrated' Tcal values are typically about a factor of two higher than what I think they should be.  Typically, I find values from 30 to 50K, while the seven antennas with lab-measured Tcals are all around 15 — 20 K.  This strongly suggests the default efficiencies used in generating the calibrated visibilities are about a factor of two too high — it looks like we're using 1.0 instead of the measured 0.45 (or so).

Rick



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