An artificial device that circumnavigates the Earth, receiving and retransmitting radio-frequency signals to multiple points on Earth. The communications hardware includes antennas, receivers, signal processing, and power amplifiers. The performance is predicted by calculating the power received by the satellite and by the receiving ground station. The satellite has solar arrays and batteries to provide electrical power, thrusters to keep the satellite in the desired position and orientation, and radiators to dissipate heat. The equipment is designed to operate unattended for many years. Many communications satellites are put in a special circular orbit high above the equator.