Communications Satellites, Part 2: Telstar and Relay

After initial experiments with passive reflectors (see Part 1), the next step in space-based communications relays were active satellites that received transmissions from Earth and retransmitted them for reception at distant locations. The first such satellites were placed in low Earth orbits (because boosters of the era could not loft a satellite into a geostationary orbit) and had to be tracked by rapidly moving antennas and could only provide coverage for a limited time before they went below the horizon. Still, these satellites provided the first live television transmissions between continents.