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.
[Illustration: _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
[Illustration: _The Telstar I satellite—inside (looking at the
electronics canister from the top down)_]
beacon transmitter
traveling-wave tube amplifier
radiation measurement equipment
nickel-cadmium cells (foamed)