Finally, the satellite had to be able to control its equipment by means of signals from the ground. To keep the solar power plant from being overloaded, there had to be some way of “commanding” the satellite to turn itself on or off. As you will read later, this was the one part of the satellite that caused us the most headaches once Telstar I got into orbit. The Telstar I Satellite—Outside Telstar’s outer appearance is very familiar by now: a 34½-inch sphere with 72 flat facets, a double row of rectangular openings circling its center, and a short, oddly twisted antenna on one end. Of the 72 facets, 60 are used for the solar cells that are the satellite’s main power source. When Telstar is in sunlight, these cells convert solar energy into electrical power; at full capacity the 3600 solar cells will supply about 15 watts. As time goes by, this power slowly diminishes as the cells are gradually damaged by such hazards of space as radiation particles and micrometeorites. To reduce this damage, the satellite’s cells are covered with a thin layer of man-made sapphire. Two bands of rectangular openings go around the center of the satellite. The smaller cavities, of which there are 72, are receiving antennas; the 48 larger ones are transmitting antennas. This arrangement allows the antennas to transmit and receive equally well in all directions—except directly along the satellite’s poles. At one end of the satellite is an entirely separate receiving and transmitting antenna that takes care of all the signals needed for Telstar’s command, tracking and telemetry. The antenna is composed of four metal loops joined in the shape of a helix. It receives the important command signals from the ground that give orders to the satellite’s equipment. It sends reports back to the ground from the special radiation measuring devices and other sensors aboard the satellite, and it also transmits the continuous 136-megacycle radio beacon that can be picked up by ground equipment searching for Telstar.