Measurement of Cross-Polarization Gains of VGOS Antennas

VGOS antennas observe in dual linear polarization mode. To obtain the maximum signal-to-noise ratio, the correlator visibilities have to be combined to Stokes I for fringe-fitting. For this processing step it is essential to calibrate the complex gain differences between the two linear feeds of each antenna. With the aim of better understanding the cross-polarization gains of VGOS antennas, we carried out an R&D session with a network of six antennas. The data allow us to measure the cross-bandpasses with high quality and to explore their temporal evolution over the six hours of the session. Here we present our results and discuss possible implications for future calibration strategies.