Profile: Communication Systems Engineer, Donald H. Martin
Chronicling the Broad Spectrum of Satellite Communications
by Donna J. Born
Systems engineer, communications generalist, historian, and author, Donald H. Martin records the remarkable evolution of communication satellites since their beginnings in 1958.
Satellite communications is the most significant application of space technology, and the definitive reference for this technology is Communication Satellites by Donald H. Martin. The book has been widely praised and recommended. E. W. Ashford, head of the Communications Satellites Department of the European Space Agency, described the third edition of Communication Satellites as "the most comprehensive such reference in the field." In his review in the international journal Space Communications, Ashford recommended the book as "an excellent source book for anyone doing research in satellite communications."
Martin, senior engineering specialist in The Aerospace Corporation's Architectures and Spectrum Management Office, has been collecting information on satellite communications since 1972, when his manager offered him a choice of assignments: of the three options, he chose to write a description of communication satellites then in orbit. The assignment grew the next year to include a report describing satellites being built, and gradually expanded to the first edition of Communication Satellites in 1986. The fourth edition, published in 2000, is more than twice the length of the first edition and is the first to use and cite Internet references.
"I had no thought at the beginning of this task that it would last 29 years, and no thought of publishing a book," Martin recalled. "The book has gradually evolved, and it's been a lot of fun." Martin wrote Communication Satellites primarily to support the needs of Aerospace customers. One of the earliest customers for the book was the Defense Department's Net Technical Assessment Office, which used the information to support its work in comparing technical capabilities and technologies. The third edition was a response to a specific request by U.S. Space Command.
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Communication systems engineer, Donald H. Martin
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Martin said the book has also become a resource for professional growth, enlarging his knowledge in the field. "On the one hand, I was gathering communication satellite information for the sake of writing or revising the book; on the other hand, I found that same information kept me up to date on satellite system design, communication technology, and related business issues. This helped me support projects I was working on," he said. "Reading about communication satellite systems developed by U.S. commercial companies and by foreign governments and companies gives a broader context that has been very useful in supporting U.S. government customers." Much of the information for his article in this issue of Crosslink on the history of military satellite communication comes from his book.
Martin joined the Communications Department in the Engineering Group at Aerospace in 1968 after receiving B.S. and M.S. degrees in engineering from the University of California, Los Angeles. He has stayed at Aerospace these 34 years because he likes the people, the opportunity to work directly with government customers, the variety of work, the environment, and the chance to interact with and to learn from specialists in many engineering disciplines. He especially likes working on requirements assessment and concept development early in the life of a program, where Aerospace has a great deal of impact on the evolution of the architecture.
He also likes the diversity of his assignments, having worked with all aspects of communications and communication satellites, both in engineering and in the program offices, providing expertise directly to government programs. "Although I am a communications engineer by training and by focus, I've found that I really enjoy the breadth of the work that I have done," he said.
Martin describes himself as a generalist who knows about communications—a systems engineer interested in the broad-scale look of space systems—rather than a technical specialist who looks at specific technology and design details. He wrote Communication Satellites in that context: "The history was done to gather information on systems, to have that broad information available when we need it to do work for customers and to answer customers' questions."
A recent Aerospace effort in which he was involved, for example, relied on such information to estimate the amount of interference between proposed government and commercial satellite systems sharing a frequency band: "We looked historically at communication satellite systems in other frequency bands or for other applications—how many were proposed, how many were licensed, how many eventually got into operation, and how long the first systems took from the initial proposal, to licensing, to operation. By looking at the historical pattern, we were able to make projections of what the environment will be in 2010 to guide us in our analyses in support of the government system."
In another effort, information gathered for the book helped to accomplish a short-term commercial project in 1999, in contrast to the long-term support to the government that is the usual Aerospace business. Martin was part of an Aerospace team that did a technical and spectrum-use risk assessment for a group of European banks that were considering a loan of several hundred million dollars to a commercial satellite company.
Many factors are involved in formulating the best system design to meet government requirements, Martin explained. Development of a satellite system has to respond to government needs, obey the laws of physics, be economically reasonable, and be compatible with available technology. "New satellites have to communicate with a large inventory of Earth terminals, ranging from units that can be carried by one soldier to terminals with 60-foot-diameter antennas anchored in concrete. With each satellite system, we're trying to do more. But we also have to be compatible with what the government already owns—what the military services have already deployed in the field."
In communication satellite technology, bandwidth and power are the primary measures of capacity. "And we always find that the users want more capacity," he said. "As the frequency at which the satellite system operates goes up, the available bandwidth goes up, but our technological ability to generate the downlink power decreases. Also, as the frequency goes up, the atmo-spheric attenuation goes up."
Current Aerospace programs to develop communication technology include wider-bandwidth equipment and higher-power, more linear amplifiers. Another is bandwidth-efficient modulation—the ability either to transmit the same amount of information in a narrower bandwidth or to use the existing bandwidth to transmit more information. "Forty years ago, civilians were happy with simple telephone service, and soldiers in the field were satisfied with poor to moderate-quality voice communications," he said. "Now the civilian world is accustomed to mobile communications, Internet access, hundreds of TV channels, and the military needs the same technologies that provide these services to give them the information superiority they need to do their jobs."
Most recently Martin has been working in the area of spectrum management—how multiple systems and diverse users share the frequencies that are practically available for use. The communications and general electronics explosion in recent years has placed increasing demand on the electromagnetic spectrum. Competition for frequencies and the greater need to share them makes frequency use a significant constraint on space-systems architectures.
 Communication Satellites, Fourth Edition, is co-published by The Aerospace Press and the American Institute of Aeronautics and Astronautics (2000, 602 pages, ISBN 1-8849899-09-8). |
"Twenty or 30 years ago, we knew certain frequencies would be available, and we designed to make use of them. Now availability of the spectrum must be looked at in the earliest stages of designing a satellite system," Martin said. "There is no easy solution. Over the decades we have used higher and higher frequencies, and we're getting to the point where atmospheric physics limits us, technology limits us."
Satellite communications has not, however, reached a limit in its evolution, Martin said, and will certainly grow over the next several decades and be applied even more widely. Eventually, if optical fiber goes to every home and every business on Earth, satellites will be used only for mobile communications to aircraft, ships, hikers in the mountains. Bringing fiber to every site, however, is not necessarily economically worthwhile. A satellite is by no means inexpensive to launch, and a satellite launched today has a design life of 10 to 15 years. But once in orbit, it can serve everybody in a large area, whether a country, a continent, or a hemisphere.
Martin has received many awards for his work, including Aerospace Team and Individual Achievement Awards and The Aerospace Corporation's President's Award, one of the company's highest honors. He has also been part of two teams that have received National Foreign Intelligence Community Meritorious Unit Citations.
Work he has done in the past has contributed to space systems now in orbit that are being used to help coordinate actions in the air and on the ground in the nation's struggle against terrorists. "Space systems take a long time to develop," he said. "Typically the government will take more than five years to prepare for a new system or a new generation for an existing system, then take five more years to develop the actual satellites and begin launching them. System architecture and space technology work that I'm doing now will see fruition in space systems launched in the 2010 to 2020 decade."
Although a fifth edition of Communication Satellites is not currently being planned, Martin expects there will be one and is looking for a coauthor. He continues to collect new information, both for the book and for use in support of Aerospace customers. "The book is one of the variety of assignments I've enjoyed during my career at Aerospace. It's been a very interesting time."
To Winter 2001/2002 Table of Contents
