What causes "spin fading" when referring to satellite signals?

Spin fading occurs as a result of the rotation of the satellite and its antennas. When a satellite is in orbit, it often spins on its axis, which can cause variations in the signal received by an Earth station. As the antenna rotates, the orientation of the transmitted signal changes, leading to fluctuations in signal strength. This is particularly significant for signals that are circularly polarized because the changes in orientation can result in varying degrees of polarization matching between the transmitted and received signals.

In this context, the rotation alters how the waves propagate and the alignment of the receiver's polarization. Hence, the impact of this rotation on the antennas significantly contributes to the phenomenon known as spin fading. Understanding this effect is crucial for optimizing reception conditions and ensuring reliable communication with satellites.