Applying JVLA switched power or ALMA Tsys using gencal

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4.3.6 Applying JVLA switched power or ALMA Tsys using gencal

Noise diodes in the JVLA antennas can be used to pre-calibrate the data. The diodes follow an ON-OFF cycle and the power for both states is measured and recorded. This is called the ’JVLA switched power’ calibration. To apply the calibration, the switched power data first needs to be filled into the measurement set via importevla and switchedpower=True (see Sect. 2.2.2). The second setp is to create a calibration table vis gencal and caltype=’evlagain’, like

gencal(vis=’test.ms’,caltable=’JVLAswitchedpower.cal’,caltype=’evlagain’)

For ALMA the calibration of system temperature is done via hot loads and the data recorded similar to the JVLA in the measurement set (ALMA will provide measurement sets where these data are available. To derive the calibration table from it, use caltype=’tsys’:

gencal(vis=’test.ms’,caltable=’ALMAtsys.cal’,caltype=’tsys’)

This calibration tables created for ALMA or JVLA are then carried along all further calibration steps in the gaintable parameter.

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