In a circularly polarized wave, the polarization rotates one full turn for every cycle of the RF carrier used for VSAT service. The propagating RF wave therefore has no fixed orientation for its electric and magnetic fields as the wave propagates, so the orientation of the antenna's transmit and receive feed have no effect on the signal level received over the link. A Circular Tube is used in the Feed for circular polarization requirements, as seen below:

You can also view the alignment of the Circular Cross-Polarization below in the VSAT Installation Manual Components Chapter: