CACAL uses a 16 cycle in-memory history of the visibilities and can
average up to 8 cycles to improve the accuracy (it actually takes
medians). It checks whether the antennas are on-source to determine if
the data is valid. For the gain calibration to function properly the
Tsys correction has to be enabled in CAOBS (this is the default
state). If two frequencies are used they are calibrated
simultaneously. Calibration of delays and phases is done relative to
the reference antenna. The XY phase (when available) is used to
calibrate the relative phase of the XX and YY polarization. Amplitude
calibration is relative to the specified flux of the calibrator (or
the average flux). All calibration corrections are stored in a 16-slot
buffer in memory, new frequency/bandwidth combinations are assigned
new slots, replacing the least frequently used slots. The default
settings are derived from the slot closest in frequency, and with the
same or larger bandwidth. There is a separate buffer for global
delays and early-normal calibration, these are determined at
reconfiguration. CACAL can also determine the polarization leakage
terms: This option is only offered in interactive mode and when on
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638.