Why were communications lost on the far side of the moon ?
The far side of the moon, also referred to as the "dark side," experiences a communication blackout due to the Moon's synchronous rotation. The Moon takes approximately the same time to complete one rotation on its axis as it does to orbit the Earth. This means that the same side of the Moon always faces towards the Earth, while the opposite side is always facing away.
In order to establish direct communication with the far side of the moon, dedicated communication satellites or relay stations are required. These satellites are placed in orbits known as Lagrange points, which are locations where the gravitational forces of the Earth and the Moon balance each other out. By positioning the satellite in a Lagrange point, it can maintain a stable position relative to the Moon and the Earth.
However, even with these communication relay stations, there are still times when direct communication is lost. This occurs when the Moon passes in between the Earth and the satellite, blocking the line of sight between them. During this time, known as lunar occultation, the satellite cannot communicate with either the Earth or the moon landers/rovers situated on the far side. Therefore, communications effectively get lost until the Moon moves out of the way of the line of sight, and the relay communication is reestablished.