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.
Six of the satellite’s flat facets are used for special measuring devices. Two different radiation studies are made: finding out how much damage will be done to solar cells and transistors, and determining how many actual energetic particles—protons and electrons—are present in the part of space that Telstar passes through. These different jobs are done by special devices on various facets. One, for example, consists of seven identical silicon transistors, six having different thicknesses of shielding and one being left unshielded—the amount of damage done to each is recorded and reported back to earth. Devices on another facet measure the radiation damage to solar cells protected by various thicknesses of sapphire. For the second radiation experiment—particle counting—four different types of silicon diodes are used as particle detectors. These measure the energy deposited both by protons of three energy levels and by electrons as the satellite passes through belts of natural and man-produced radiation in space.
The Telstar I satellite—outside
telemetry, command and beacon antenna solar cells for power supply solar cells to measure radiation damage receiving antenna transmitting antenna transistors used to measure radiation damage solar aspect cells mirror
The Telstar I satellite—inside (looking at the electronics canister from the top down)