Communications satellites have changed the way we live. What exactly are they? How do they work? What does the future hold for them?
Communication satellites are the way that radio, telephone, and television have overcome limits and linked the world through instant communication. They way they work and how they carry messages from one place to another all over the world is a miracle of the modern age. It is the use of these satellites that have changed and will continue to change the way so much of today’s communication is done.
The first successful communications satellite was Telestar, which was launched in the early 1960’s. Telestar was little more than a reflective metal surface. The satellite worked by using a radio signal, which was sent into space and bounced off the satellite’s surface and picked up by stations on the ground. Telestar was an experiment that proved the worthiness of the idea.
By the 1970’s the manned space program had pushed the development of technology to the point where relatively small (10 feet or so in diameter) but powerful earth receiving antennas became practical for getting signals from space. This along with advancements in circuit miniaturization made the concept of communication satellites practical and cost effective in many applications. By the end of the decade commercial television and telephone signals were being sent by satellite relay from earth to earth. The birth of the television super station; nationwide/worldwide live broadcast; and international facsimile all came about by the end of this decade.
In the 1980’s and 1990’s there was a growth in the number and sophistication of communication satellites. Satellite use for telephone and television paralleled the development of the geosynchronous orbiting satellites. These satellites orbit earth at an altitude of 22,300 miles (35,900 Km) in a band above the equator and they remain fixed directly above a stationary point on earth. Solar panels or onboard nuclear reactors and relay signals from earth using low power microwaves power these communication satellites. While a majority of communication satellites are in these geosynchronous or geostationary orbits, new technologies driven by the need to overcome the limited number of spaces available to these satellites has developed.
As we begin the new century a number of new types of communication satellites are being developed for use in space, including Low-Earth orbit, or LEO satellites. The need for these low orbiting satellites is based on a number of problems made by the very nature of geostationary satellites. There are limited positions available for placement of satellites along the geosynchronous belt, and the size and power of the rockets needed to propel these satellites into position make these platforms very expensive to place and maintain. There is also the problem of time delay on these geosynchronous satellites. Because the round trip time for signals traveling from the ground through the satellites to the ground is approximately ¼ of a second, it tends to cause difficulties with voice communication by telephone. The LEO would work to overcome these problems by using numbers and lower orbits.
The LEOs orbiting at between 400 and 1,000 miles could be put up in groups of up to several thousand, linked to each other and the ground they would be much less expensive to place and maintain and would need less attention paid to precision in their orbit. These satellites would be ideal for telephone communication and one company already has over 300 of them in place world wide for long-distance telephone communication. LEOs are but one type of alternative solution to geostationary communication satellite. There are also plans for satellites in deep space orbit over 100,000 miles above the earth, which would have the ability to relay messages and would not have the difficulty of maintenance of either of the other two types of communication satellites
Deep space orbiting satellites are ideal for relays that are not time critical. While telephone, live television and radio might not be ideal, for most entertainment and other programs and communications these high orbit satellites would be ideal. There is also an aspect of these satellites being used as orbiting, manned manufacturing plants and communications relays. One suggestion for the placement of these platforms is in the location where the earth’s and the moon’s gravitational pull exactly match and neutralize each other. This location is called L5 space. There are groups today that actively lobby for this use of space technology.
Communications in space was almost an unbelievable proposition in the first half of the 20th century, in less than 40 years it has moved form a dream to practical reality. Today satellite antennas for television are found on homes and are only 18 inches in radius! PCS satellite mobile phones are common and inexpensive. As the communication satellite and its technology continue to evolve and grow it will continue to change the way we keep in touch around the world.