B The Navy and Satellite Communications

INTRODUCTION

The U.S. Navy, with its global sea-based operations, has always had to depend on electromagnetic communications. At first, of course, it employed optical frequencies (flags and lights), but early in the 20th century the Navy turned to radio and pioneered its early use. Working closely with industry, the Navy developed the technology for low- and medium-frequency transmission. RCA (then the Radio Corporation of America) was formed at the request of the Navy to provide a commercial radio service with David Sarnoff, a former Marine radio operator, at its helm. After World War I, the infant Naval Research Laboratory (NRL), under the guidance of Thomas Edison, embarked on a highly productive research effort in radio propagation, which developed a quite novel technique for radio detection and ranging, called ''radar."

As the space age dawned in the 1950s, the U.S. Navy was highly experienced in radio technology and operations and prepared to utilize satellite communications. Indeed, the Navy can claim the first operational use of an Earth-orbiting satellite for communications—six years before Sputnik!

EARLY SATELLITE COMMUNICATIONS

Navy Satellite Communications

In 1951, NRL demonstrated the feasibility of bouncing radio signals off Earth's natural satellite, and in July 1954 actually transmitted the first voice



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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare B The Navy and Satellite Communications INTRODUCTION The U.S. Navy, with its global sea-based operations, has always had to depend on electromagnetic communications. At first, of course, it employed optical frequencies (flags and lights), but early in the 20th century the Navy turned to radio and pioneered its early use. Working closely with industry, the Navy developed the technology for low- and medium-frequency transmission. RCA (then the Radio Corporation of America) was formed at the request of the Navy to provide a commercial radio service with David Sarnoff, a former Marine radio operator, at its helm. After World War I, the infant Naval Research Laboratory (NRL), under the guidance of Thomas Edison, embarked on a highly productive research effort in radio propagation, which developed a quite novel technique for radio detection and ranging, called ''radar." As the space age dawned in the 1950s, the U.S. Navy was highly experienced in radio technology and operations and prepared to utilize satellite communications. Indeed, the Navy can claim the first operational use of an Earth-orbiting satellite for communications—six years before Sputnik! EARLY SATELLITE COMMUNICATIONS Navy Satellite Communications In 1951, NRL demonstrated the feasibility of bouncing radio signals off Earth's natural satellite, and in July 1954 actually transmitted the first voice

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare message over the Earth-moon-Earth path. The Navy then established an operational link between Pacific fleet headquarters in Hawaii and the Chief of Naval Operations (CNO) in Washington, D.C., carrying 16 channels of 60 words-per-minute ultrahigh-frequency (UHF) teletype for periods of 4 to 7 hours each day (depending on the moon's declination). As satellite communications systems go, moon relay rated fairly low on capacity and data rate, but extremely high on reliability—with negligible launch cost. In 1962, the U.S. Navy took a significant step forward, building the first satellite communications ship, the USNS Kingsport, mounting a 30-foot stabilized antenna to provide a mobile terminal capability for the National Aeronautics and Space Administration's (NASA's) Syncom satellite. Kingsport, in the harbor of Lagos, Nigeria, relayed the first telephone call ever over a geostationary satellite, from President Kennedy via the Syncom II satellite. Kingsport later provided communications services in the Pacific and Indian Ocean areas for several years in support of tracking and recovery operations for NASA's Gemini program. Early Experimental Programs Within a year after the first Sputnik, the Department of Defense (DOD) and NASA initiated a number of experimental satellite projects that set the stage for operational military and civilian systems. Score and Courier, developed and launched by DOD in 1958 and 1960, respectively, were the first communications satellite experiments. They demonstrated that delicate and complex electronic equipment could survive the trauma of launch and could operate in orbit. NASA's entry was Echo, a 30-meter-diameter metal and plastic balloon, launched in 1960 to demonstrate passive satellite communications. Echo carried the first transoceanic satellite signal from Bell Laboratories in New Jersey to the French Communications Center in Paris. Telstar, a medium-altitude satellite developed by AT&T Bell Laboratories and launched in 1962, was the most famous experimental satellite—its technical contributions so significant and its impact on the public so great that its name for a while became generic for "communications satellite." It was the first satellite to use a traveling wave tube (TWT). Significantly, Telstar received at 6 GHz and transmitted at 4 GHz, bands that later were assigned to commercial service and used by INTELSAT and all other fixed-service systems during the 1960s and 1970s. Telstar carried the first live television from the United States to England and France. NASA's Relay satellite, a medium-altitude system like Telstar, launched a few months later, introduced additional technologies and provided extensive communications links, including the first between the United States and Japan. NASA's Syncom satellite, built by Hughes and launched in 1963, was prob-

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare ably the single most important step in the development of satellite communications. It was the first satellite placed in geostationary orbit and became the model for many generations of operational spacecraft to follow. Other early experimental satellites that deserve mention include the six NASA advanced technology satellite (ATS) series and the DOD leading-edge services (LES) and tactical satellites (TacSats), all of which made important technical contributions in developing spacecraft subsystems, Earth stations, and transmission systems and in opening up new frequency bands (specifically UHF, L, C, X, and Ka-bands). All of this experimental satellite work, conducted by the U.S. government throughout the 1960s and into the early 1970s, made military and commercial satellite communications possible and led to a thriving international industry. The Navy participated in many of these programs, developing and testing terminals, multiple access, fleet broadcast, and antijamming technology. Early Commercial SatCom In July 1961, President Kennedy issued a policy statement, declaring that the United States would develop a global satellite communications system, not through the government or the monopoly carrier, AT&T, but through a new commercial entity, and with international cooperation. Following the presidential lead, the U.S. Congress passed the Communications Satellite Act of 1962 to form Comsat Corporation. The United States then joined with 10 other nations to form the international body known as INTELSAT. And in April 1965, less than four years after the concept was suggested, the world's first commercial satellite, INTELSAT I, known as Early Bird, was launched, and operational telecommunications service inaugurated between North America and Europe. This first satellite link carried 240 telephone circuits at $32,000 per circuit-year compared with the single undersea telephone cable then existing, which carried only 150 circuits at about $100,000 each. The satellite also had a unique broadband capability, frequently demonstrated, to carry television across the ocean with the phrase "live via satellite." TECHNOLOGICAL PROGRESS From the start, technological and operational progress in commercial satellite communications was very rapid. By the end of its first decade, INTELSAT was well into the fourth generation of successively larger, more powerful satellites (Table B.1) providing global coverage, connecting hundreds of Earth stations, and carrying thousands of telephone circuits plus television and data. With more powerful satellites came the opportunity to shrink the size of Earth stations that could then be customized to fit users' requirements—located on a rooftop, for example, or on a moving platform such as a ship or submarine.

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare TABLE B.1 INTELSAT Satellites   INTELSAT I INTELSAT IV delta First launch 1965 1971 6 years Weight 38 kg 700 kg 18x Power 40 W 700 W 17x Bandwidth 50 MHz 400 MHz 10x Capacity (circuits) 240 4,000 16x Cost/circuit-year $32,000 $1,200 -96% Microwave technology moved ahead rapidly in the 1970s, bringing improved TWT and solid-state power amplifiers, microwave integrated circuits, and multibeam antennas. These technologies led to the development of domestic satellite systems in several countries—in Canada (1972), the United States (1974), and Indonesia (1976). Mobile and Broadcast Services It was obvious from the start that communications via satellite offered two exceptionally valuable capabilities: Mobility: the capability to provide two-way communications to a moving platform—be it a ship at sea, airplane in flight, or automobile on the highway. Broadcast: the capability to transmit to multiple receivers simultaneously over a wide area (as much as one-third of Earth's surface from a single geostationary orbit satellite). These two capabilities were exploited to a limited extent early on in the INTELSAT system, but starting in the 1970s, separate systems were established to provide mobile and broadcast services. A set of experiments demonstrating reliable ship-to-shore service via INTELSAT IV conducted in 1973 on the ocean liner Queen Elizabeth II stimulated interest in the U.S. Navy in filling the gap before its then delayed and overbudget Fleetsat system would be ready for launch. This led to Marisat, the first mobile satellite communications system, which was established in 1976 to provide UHF service to the Navy and L-band service to the commercial maritime community. The L-band capacity of Marisat was later incorporated into the INMARSAT system. This is an excellent example of a successful combined military-civil system. INTELSAT, in the 1960s, provided the first capability to transmit television across the oceans for what was termed "occasional use," representing about 1 percent of INTELSAT's revenues. In the 1970s, U.S. domestic systems began

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare carrying full-time television across the country for the three networks then in existence. With the explosion of cable television in the mid-1970s and through the 1980s, domestic satellites came into demand to provide service to cable heads. This in turn introduced the possibility of many networks. Also, the opportunity was created for anyone, particularly in a remote area lacking over-the-air or cable service, with the expenditure of only a few thousand dollars, to obtain his own small Earth station. With that, he could receive the same channels carrying television traffic to cable head-ends. By the mid-1980s, there were over a million such terminals on farms, ranches, and even suburbs of major cities—and the broadcast satellite industry was born! Europe and Japan beat the United States in introducing so-called direct broadcast satellites (DBSs). These satellites have enough effective radiated power to broadcast into a small dish (less than 1-meter aperture), easily mounted on a rooftop and costing a few hundred dollars. By 1992, there were an estimated 5 million DBS terminals in Europe and Japan. In the last two years, with the launch of Direc TV by Hughes Communications, each satellite carrying 75 digital television channels, the United States stepped ahead of the rest of the world technologically. There are now some 20 million DBS terminals worldwide, including a rapidly growing population throughout the Far East. The Navy has helped foster defense-wide interest in a global broadcast service through such projects as Radiant Storm, which explored the use of small antennas with high-power Ku-band downlinks for broadcast distribution. The Navy introduced satellite broadcast in defense satellite communications with the creation of fleet satellites in 1972. Digital Satellite Communications Because power and bandwidth are such precious commodities in the geostationary orbit, satellite systems have led the way in one of the most important developments in telecommunications—the shift from analog to digital processing and transmission techniques. Digital techniques (e.g., pulse code modulation [PCM] coding, phase shift keying [PSK] modulation, time division multiple access [TDMA]) were rapidly developed and introduced in satellite communications systems starting in the mid-1970s, and installed in many systems in the 1980s, to provide efficient data compression, demand assignment, and multiple access systems. COMMERCIAL SATELLITE COMMUNICATIONS TODAY Satellite communications today is a big global business—exceeding $20 billion per year, including revenues from satellite-borne traffic and sales of spacecraft, launch vehicles, Earth terminals, and transmission equipment. All of these segments appear to be highly profitable, with various services—telephone, tele-

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare vision, and data; fixed, broadcast, and mobile—growing at annual rates of 10 to 40 percent. As the first and still the only significant commercial payoff from space, satellite communications continue to provide substantial return for every dollar invested in R&D. More than 200 countries and territories are currently involved in satellite communications. INTELSAT alone has 140 member countries. Fifteen countries have significant industrial capacity related to satellite communications. There are some 30 national, regional, and international satellite communications systems in operation employing more than 200 satellites in geostationary orbit. Tens of thousands of large Earth stations ranging from 3 to 30 meters, more than 200,000 very small aperture terminals (VSATs) (1 to 3 meters), 20,000 shipboard terminals, and 20 million direct broadcast receiving terminals (less than 1 meter) are in operation, carrying voice, video, and data traffic to international capitals and remote villages, to ships at sea and aircraft in flight, around the globe and around the clock. Highly portable voice-grade transceivers the size of a laptop, selling for about $5,000, are now in use, with advanced systems planned for the late 1990s, promising hand-held units similar in weight and cost to a cellular phone. Of the three satellite communications services—fixed, mobile, and broadcast—only the first may be considered really mature, growing at rates of 5 to 10 percent per year. Within the fixed service, telephone traffic seems to be flat or decreasing, television distribution is increasing slowly (offset somewhat by gains in transmission efficiency), and VSAT systems are increasing rapidly (but account for relatively little transponder capacity). Broadcast and mobile satellite services are growing rapidly, increasing numbers of terminals, amount of traffic, and revenues from 20 to 40 percent per year. The next move in mobile systems will be to the use of hand-held units for what is being termed "personal service." This service may be provided by either a few large, powerful satellites in geostationary orbit or by a larger number of satellites in lower orbit (as noted in the following section). LEO vs. GEO Systems For three decades all commercial communications satellites have operated in geostationary orbit, which has several advantages, primarily that "one satellite makes a system." A geostationary orbit (GEO) spacecraft can provide greater communications capacity per pound in orbit or per unit of launch cost than can a set of low Earth orbit (LEO) spacecraft. Also, a GEO satellite's power and bandwidth may be configured to match communications requirements through the use of multibeam antennas and spot beams, weighted and shaped beams, and efficient demand assignment and multiple access techniques. The advantages of LEO and medium Earth orbit (MEO) over GEO for communications satellites lie in decreased transmission delay time and full global

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare coverage. Also, whereas aperture size is limited for GEO satellites, LEO satellites can provide a greater flux density to a given small area on the ground, allowing use of smaller terminals. This is a very appealing argument for the use of LEO systems intended to communicate with hand-held terminals. In the past, low- and medium-altitude satellites have been employed for remote sensing, for scientific measurements, and for certain military missions in order to get full global coverage (including the poles) and the highest possible resolution (for limited aperture size). These systems have used relatively few satellites and launches. The largest currently operating system is the Global Positioning System (GPS) with 24 satellites. There has been no government or commercial experience with large numbers of satellites in precisely spaced orbits as required in certain proposed systems (see next section). LEO and MEO Systems Four low- or medium-altitude (LEO/MEO) multiple-satellite L-band (and S-band) systems—Iridium, Globalstar, Odyssey, and ICO—are currently under development, each aimed primarily at providing mobile voice-grade service to hand-held sets. All are in direct competition with each other and with existing and proposed GEO mobile systems. The LEO/MEO systems are all going through the tortuous process of applying for licenses, requesting frequency applications, seeking investors, lining up international partners, organizing contract teams, conducting system and marketing studies, doing detailed design work, and letting construction contracts. Iridium is a system funded and under development by Motorola Satellite Communications, Inc., with Lockheed as the spacecraft builder. Its estimated cost is $3.4 billion. Globalstar is under development by Loral Qualcomm Satellite Services, Inc., and is estimated to cost $1.8 billion. Odyssey, proposed by TRW, Inc., is estimated to cost about $2 billion. ICO. INMARSAT conducted a set of system concept and design studies over the last five years under its "Project 21" to determine the optimum nature of a system for its entry into the personal service market. It split off an affiliate company in 1994 called ICO to build a system of 12 medium-altitude satellites in two orbital planes. It conducted a competition and recently awarded a contract to Hughes to build satellites. The ICO system is estimated to cost $2.6 billion. Some major characteristics of the three systems mentioned above are shown in Table B.2. All four of the LEO/MEO systems (Iridium, Globalstar, Odyssey, and ICO) are being proposed by competent and experienced organizations—three U.S. aerospace companies (Motorola-Lockheed, Loral, and TRW) and the interna-

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare TABLE B.2 Major Characteristics of Iridium, Globalstar, and Odyssey   Iridium Globalstar Odyssey Altitude 785 km 1,401 km 10,335 km Constellation 6 × 11 = 66 8 × 6 = 48 3 × 4 = 12 Weight 680 kg 400 kg 1267 kg Crosslinks 4 × 23 GHz None None Data rate 4.8 kb/s 1.2-9.6 kb/s 1.2-9.6 kb/s Multiple access TDM CDMA CDMA Processing Switch & routing None None Capacity 3,840 circuits >2,800 circuits 2,300 circuits Terminal price $2,000 to $3,000 $750 <$500 tional INMARSAT consortium. All four systems appear to be technically feasible. However, all face technical problems, coupled with some level of financial, organizational, and/or political difficulties. It is not at all clear how many of the four will survive the development process, and if so, how well the survivor(s) can compete with each other. These systems are potentially significant to naval operations because, while basically directed at land-based users, they inherently cover the broad ocean areas and the polar regions that may generate little commercial traffic. But the Navy can benefit from the low-cost access available through these systems for logistic and administrative traffic, including sailor access to direct-dial calls to home for quality of life improvement. In addition, these systems are built around very small, low-cost terminals, thereby making their adoption by the Navy cost-effective. Competitive Services It is important to note that all three services—fixed, broadcast, and mobile—have competitive terrestrial systems (Table B.3). The claim for a role of satellites in the global information infrastructure currently being voiced by the satellite communications community generally emphasizes the wide-area coverage, the mobility, and the distance-insensitivity TABLE B.3 Competitive Services Service Competitor Satellite Advantage Fixed Optical fibers Multinode networks Broadcast Cable networks Wide-area coverage Mobile Cellular Wide-area coverage

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare to cost that satellites provide. These capabilities give satellite communications an enormous and unchallenged advantage in the broadcast and mobile services. The networking advantages of satellites over cable as applied to the fixed service are somewhat more subtle (as treated in the following sections). Fixed Service Future Within the fixed service, sparkling new opportunities appear to lie in high-data-rate networks—the market created by the introduction of optical fiber cables into local and regional telecommunications systems. The question seems to be whether satellites will have a significant role in interconnecting these local and regional networks into national and international ones, or whether fiber will overwhelm the global information infrastructure. The rapid growth in telecommunications around the globe is causing a demand for ever higher data rates. Many businesses today are subscribing to integrated services digital network (ISDN) service (64 kb/s), and corporate networks are going to T-1 (1.5 Mb/s). Research centers are requesting T-3 (45 Mb/s). National and international carriers (including the Internet backbone) are now employing OC-3 (155 Mb/s). "Gigabit testbeds" (such as those in the U.S. High Performance Computing and Communications program) are operating at OC-12 (622 Mb/s) and OC-48 (2.4 Gb/s), and advanced technology experiments are pushing to rates as high as 100 Gb/s. Military requirements in almost all respects mirror commercial requirements. In some but not all cases military requirements lead civil applications. There is little doubt that the first decade of the next century will see military operational requirements emerge for all of these high data rates. In the case of the Navy, high data rates will be needed for imagery and other sensor data that may be associated with cooperative engagement capability, cruise missile retargeting, video conferencing, medical services, and training using "virtual reality." Networks Satellites are bound to play an important role in future high-data-rate networks, as they have in networks at lower data rates. If several widely separated sites are to be interconnected, satellites can provide significant performance and cost advantages over cables. If many sites are to be connected, satellites win handily. Because of satellites' wide-area coverage, and their valuable demand-assignment and multiple-access capabilities, these advantages increase with: The number of nodes in the network, The distance between the nodes, The variation in traffic loading on network paths, and

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare The existence of geographic or political boundaries between nodes in the network. These four factors all contribute to the preference for satellite-based networks in transcontinental, transoceanic, and international service. In addition to multinode networks, a traditional niche for satellites has been in "thin route" service, and they will undoubtedly be so employed in the future. Although it seems strange now to think of an OC-3 link as thin, when the world is girdled with multigigabit fiber-optic networks, links to remote areas carrying only 155 Mb/s will be considered thin—and will just as surely be carried by satellites then as they are today. Satellites, with their multiple-access demand-assignment capabilities can provide great flexibility as well economy to networks. One satellite transponder, for example, may be used as a transmission channel between Italy and Canada at one instant of time, and then a millisecond later, between England and Mexico, adjusting rapidly to traffic loading. This network advantage for satellite service is very clear in VSAT systems in which the national switched telephone system is bypassed. Examples are as follows: The General Motors Corporation has a 9,000-node VSAT network connecting its offices, factories, suppliers, and dealers. Many stores and hotel chains, even gas stations (e.g., Wal-Mart, Kmart, Sears, Holiday Inn, and Chevron) employ VSAT networks for administrative service, reservations, and credit card verification. Current VSAT systems operate at low data rates (fractional T-1) but will inevitably move up the data rate scale. This same advantage will also exist at higher data rates; i.e., what is true at T-1 today will be equally true at 30 times the rate (T-3) tomorrow, and at 100 times the rate (OC-3) the day after. Indeed, calculations (by AT&T) show that for satellite service to be more cost-effective than terrestrial service between two sites in the United States, they need to be separated by 5,000 kilometers; for three sites, 3,500 km; four sites, 1,300 km; and five sites, only 800 km. Of course, for many sites, say 100 or more, the satellite's advantage is overwhelming. Satellite-based networks have additional advantages in terms of mobility and transportability—factors that are important for video news coverage, emergency service, and military use. Satellite ground terminals may be installed much more quickly than cables can be laid. Incidentally, satellites can be, and often have been, used for restoral of cable services. The use of satellites in providing emergency communications after the Kobe earthquake was a striking example of this. It is most likely, then, that satellite-based networks for high-data-rate digital transmissions will have their maximum use in multinodal, transcontinental or

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare international linkages, particularly when subject to dynamic loading and where cost, flexibility, or mobility are important considerations. The High-Data-Rate Market What will the future requirements for national and international high-data-rate service be? First, we can assume that some of the same services now being provided at medium rates, such as T-1 and T-3, will be provided at higher rates in the next decade, increasing by factors of 10 every few years. Also, we might note that since computer and communications technologies are merging and that computers are running faster and faster, data links will go to higher rates. A driving force in high-performance networking today is the need for distributed processing in computationally intensive science, engineering, and military applications such as climate modeling, computational fluid dynamics, aircraft design, or battlefield information collection and analysis. These applications will require interconnectivity among supercomputers, high-performance servers, large databases, and remote input/output. Many require distribution of interactive video (at tens of megabits per second). Some require multichannel video coupled with fast access to large remote databases and visualization—and these mean even higher rates, in the range of hundreds of megabits per second. Once the computing and communications capabilities have been combined and the networking technologies developed to serve science and engineering applications, their use in industrial and commercial applications will surely follow—and on a worldwide basis. ACTS NASA's Advanced Communications Technology Satellite (ACTS) represents a $700 million investment by U.S. taxpayers, and a return after two decades to government-sponsored satellite communications R&D. ACTS was launched in September 1993 after a 10-year development period and is operating successfully in orbit with 3 to 4 years of expected useful service life remaining. ACTS was originally intended to accomplish two objectives: Develop advanced technologies, and Demonstrate new applications. ACTS has accomplished its first objective with flying colors. It has shown that its advanced technologies (Ka-band, microwave matrix switch, multiple hopping-beam antenna, baseband processor) work in orbit. ACTS is making excellent progress toward its second objective. It has already demonstrated its prowess at modest data rates, enabling experiments to be conducted in many fields—in banking, distance learning, telemedicine, and military and mobile service. But

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare ACTS' most significant set of demonstrations—those at a high data rate—are just getting under way. ACTS has a unique capability, the value of which could not have been appreciated when ACTS was designed more than 15 years ago. By virtue of the bandwidth available to it at Ka-band, ACTS can transmit digital signals at rates of up to 1 Gb/s. With five newly developed high-data-rate terminals, ACTS is demonstrating its ability to transmit at SONET rates of 155 and 622 Mb/s (OC-3 and OC-12). One of ACTS' most demanding experiments is in supercomputer networking, in which a Cray supercomputer at the NASA Goddard Space Flight Center in Maryland is being connected with another Cray at the Jet Propulsion Laboratory in California through the satellite at OC-3 (155 Mb/s). In another experiment, now in progress, the Keck telescope in Hawaii is being connected to the astronomical data processing facility at the California Institute of Technology to perform a set of experiments in remote facility control and data visualization and analysis. ACTS has also been used for mobile communications experiments in aircraft and land vehicles. In one demonstration, called Aries, ACTS carried seismic data used for oil exploration from a ship in the Gulf of Mexico to a petroleum research center using asynchronous transfer mode (ATM) at data rates of 2 Mb/s. Commercial Ventures The Navy encountered several problems during the Gulf War in disseminating large volumes of information to commands and ships at sea. In many instances, military communications had to be supplemented with commercial satellite communications units. Navy ships found commercial INMARSAT terminals to be more reliable and user friendly than military terminals. As a result of this experience the Navy embarked on several ventures to test and evaluate the use of commercial satellite communications technology and systems. Starting in 1992, under a project known as Challenge Athena, a number of demonstrations have been conducted at T-1 (1.5 Mb/s) using INTELSAT C band services that have shown a considerable advantage over DSCS. The USS George Washington (CVN-73) and eight other capital ships have conducted demonstrations via commercial satellite communications in subjects such as the following: National primary imagery dissemination, Intelligence data and tactical imagery transfer, DSCS emergency communications restoral, Video teleconferencing, Telemedicine, and Dial-up telephone service (''sailor telephone").

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Technology for the United States Navy and Marine Corps, 2000-2035: Becoming a 21st-Century Force, Volume 3 Information in Warfare Challenge Athena has provided a convincing demonstration to the Navy that: High-data-rate satellite communications links to ships at sea are extremely valuable; and Use of commercial satellite communications technology and systems is a cost-effective way to obtain reliable, high-quality, high-data-rate services. In late 1996, an ACTS mobile terminal was installed aboard the USS Princeton (CG-59), an Aegis guided-missile cruiser, to demonstrate naval applications at 1.5 Mb/s. A primary purpose of this installation is to demonstrate the capability of loading the large Aegis missile database while the ship is at sea. Future plans as part of Project Aries are to use the NASA ACTS and tracking and data relay satellites (TDRS) to provide data links to ships at sea at 6 to 10 Mb/s at both Ku- and Ka-bands. Over the years, the Navy has been the primary proponent of satellite broadcast services, stemming from the widespread use of HF fleet broadcast in earlier days. Because of this interest, a wide-band 20-GHz broadcast capability is being added to a future UHF follow-on (UFO) satellite for DOD use. SUMMARY Satellite communications is a dynamic, high-technology, international, commercially successful enterprise, capable of providing a wide variety of services, in a reliable, cost-effective manner, to users of many types. Commercial satellite communications systems offer a wider array of services, some with higher performance, and most at lower cost than the Defense Satellite Communication System (DSCS) or other military satellite communications systems. Commercially available mobile and broadcast satellite communications services offer extremely valuable cost-effective capabilities to the Navy. Commercially available medium-data-rate satellite communications services (1.5 to 45 Mb/s) and high-data-rate services (>155 Mb/s) now being demonstrated offer the potential of new and innovative capabilities to the Navy.