Telstar-I Results
November 1962 Radio-Electronics

November 1962 Radio-Electronics [Table of Contents] Wax nostalgic about and learn from the history of early electronics. See articles from Radio-Electronics, published 1930-1988. All copyrights hereby acknowledged.

Telstar 1 was a ball-shaped satellite about 33 inches in diameter with a launch weight of 170 pounds. Its outer surface had 72 flat facets, 60 of which had a total of 3600 solar cells to recharge 19 Ni-Cad cells. On three facets were mirrors to reflect the sunlight to earth for optical tracking. That was the state of the art in 1962, when Radio-Electronics magazine editor Hugo Gernsback reported on its unqualified success. The September issue contained technical details on the Telstar 1. It sported 93 dB of receiver gain. In 1960, Mr. Gernsback wrote about "Future Space Traffic" in November 1960, where he predicted "tens of thousands of spacecraft will soon be aloft." He didn't know how right he was. In the last decade alone, thousands of satellites have been launched, many being parts of the massive satellite constellations in low earth orbit (LEO) for providing Internet service. As someone who frequently observes the night sky with binoculars and telescopes, I can attest to how you cannot look at an area of the sky even the size a couple moon diameters (d_moon~0.5°) without seeing a satellite pass by within a couple minutes. Decades ago, it was kind of cool to spot one soaring by, but now it is annoying. When astrophotography was done using photosensitive film, a passing satellite or aircraft produced a streak across the field. Nowadays, using digital photography and image processing software, removing the streaks is relatively simple. Long-exposure images now are typically made by combining multiple images of shorter exposure images of the same region of the sky, using a "stacking" technique.

Telstar-I Results

... One of the Most Complex Electronic Space Devices Scores ...

By Hugo Gernsback, Editor

Since its successful launching on July 10, 1962, Telstar I has surpassed the fondest hopes of its designers. At the moment its telemetry indicates perfect working of all its electronic-mechanical instrumentation. Although Telstar could probably stay in orbit for 200 years, its electronic equipment will be automatically shut off after about two years, to clear the frequencies for other Telstars.

As described in Radio-Electronics in September, 1962, its ball-shaped dimensions are about 37 inches diameter (axial), 34 inches equatorial. Its total space weight is 170 (earth) pounds: Its outer surface carries 72 flat facets, 60 of which have a total of 3600 solar cells which continuously recharge 19 nickel-cadmium cells when in direct sunlight. On three facets are mirrors to reflect the sunlight to earth for optical tracking.

Telstar obtains all its power from the sun via its solar cells, at the rate of 13.5 watts output. This may decrease, according to its builders, to 11.5 watts because of the effects and the impact of various charged particles.

Telstar's orbit is quite elliptical - purposely so. At its highest, it soars to 3501.8 statute miles (apogee); at its lowest it is 593.4 miles (perigee). Its period of revolution around the earth is 157.8 minutes.

Around the satellite's equator it carries one receiving and one transmitting antenna for communications and transmission of a precision tracking signal. Above its axis there is a wire-helix antenna for telemetry, command and continuous beacon circuits.

Telstar I was designed chiefly as an orbiting experimental broadband microwave space relay station. It receives earth radio signals at a frequency of 6390 megacycles, amplifies these and retransmits them back to earth on 4170 mc. It can do so only in straight lines, however, because of the curvature of the earth, which limits its total range. It must be "visible" to both sending and receiving stations simultaneously. The very weak signals received by Telstar are first transformed to a 90 mc intermediate frequency, then amplified about a million times, then transformed to 4170 mc. A traveling wave tube provides final amplification, an additional 5000 times. Total amplification is about 2 billion times. When retransmitted to earth, the signal has a power of 2 1/4 watts.

Telstar is pressurized internally with an atmosphere of carbon dioxide (CO₂), Its special instruments for that purpose, after many weeks, show that meteorites have not pierced Telstar's skin so far. The internal temperature averages 75° F. This drops 40° more or less when Telstar dips into the Earth's shadow, down to about 35° F. The outside skin temperature of the station varies from 18° F. in the shadow to 48° F. in the sun.

The greatest enemy of Telstar thus far is not micro-meteorites, or even small meteorites, but radiation. This may be of solar origin, such as solar X-rays, ultraviolet rays, etc., or Van Allen belt charged particle radiation, as well as possible damage from the artificial new belt caused by last summer's US nuclear explosions in space. Not protected by the Earth's vast blanket of atmosphere, Telstar gravitates in space, a naked target for the all-powerful cosmic rays as well.

Fully aware of this, its designers planned a number of experiments to measure the effects of radiation on electronic gear. Telstar's outer skin carries six differentially shielded silicon transistors, all radiation-sensitive. It appears that space radiation has progressively weakened these transistors. Thus the current gain of the least heavily shielded transistor decreased by a factor of 8.

Furthermore, solar cells deteriorate steadily by radiation bombardment. It appears that the least shielded solar cells, protected only by 20 mils of synthetic sapphire, decreased by about 10% current output after two weeks in space. For those protected by 25- and 30-mil shields of sapphire, the current decrease was only about 5%.

Electronic people will not be too surprised that inside Telstar's small body, aside from its voluminous electronic and other gear, there are 1064 transistors and 1464 diodes! Surprisingly enough, there is only one lone vacuum tube on board! This is the foot-long traveling wave tube already mentioned. Its inventors were Drs. John R. Pierce and Jack A. Morton of Bell Telephone Laboratories, Inc.

Bell Telephone Laboratories was responsible for the design and construction of Telstar I. The American Telegraph and Telephone Co. paid the entire cost of the Telstar project, including a fee of $3 million paid to National Aeronautics and Space Administration for launching it into orbit.

Inasmuch as a single satellite cannot give continuous worldwide service, it will be necessary to put up a multiplicity of Telstars, so there will always be several above the horizon. This makes for a minimum of 30 to 50 communication satellites within 10 years.

However, once we have sufficiently powerful rockets to launch them, future, more sophisticated Telstars can be elevated to a height of 22,238 miles above the equator. At this height they will revolve with the speed of the earth and will hover, apparently stationary, over the circumference of the earth.* At this height, we require only 3 Telstars. However, at such an elevation we meet with a disagreeable time lag because it takes a signal 0.3 second to travel both ways. In a 2-way telephone conversation there would be a 0.6 second lag between speaking and hearing the reply. This might be annoying in telephone conversations. The time lag however would not affect TV transmission and reception.

A compromise of 4 or 5 Telstars lifted to a height of about 10,000 miles, as pointed out in our March, 1958 editorial, might be a solution. This would make it possible to carry a traffic of over 10,000 simultaneous telephone conversations plus other traffic, such as world-wide television and various other requirements. It probably can be accomplished before 1975, in the writer's estimation.

* See also editorial "Satellite Electronics," March 1958, Radio-Electronics, page 33. Also "Future Space Traffic," November 1960, page 33.