The Aerospace Corporation Homepage Search Our Site About Us News Programs Capabilities Careers Education Publications PUBLICATIONS Crosslink Future U.S. Military Satellite Communication Systems Current Issue Glen Elfers and Stephen B. Miller The current military satellite communications network represents decad Previous Issues technology. To meet the heightened demands of national security in the years, newer and more powerful systems are being developed. Headlines Advances in information technology are fundamentally changing the way military conflicts ar Search Crosslink ability to transmit detailed information quickly and reliably to and from all parts of the globe w streamline military command and control and ensure information superiority, enabling faster Contact Us highly mobile forces capable of adapting quickly to changing conditions in the field. Satellite communications play a pivotal role in providing the interoperable, robust, "network-centric" c needed for future operations. Military satellite communications (or milsatcom) systems are typically categorized as wideband, protected, or narrowband. Wideband systems emphasize high capacity. Protected systems stress antijam features, covertness, and nuclear survivability. Narrowband systems emphasize support to users who need voice or low-data-rate communications and who also may be mobile or otherwise disadvantaged In 1997, the Senior Warfighters' Forum established a road map cha (because of limited the course of military satellite communications through 2010. In 200 terminal capability, there will be course corrections as the Department of Defense purs antenna size, aggressive acceleration in the delivery of improved communications environment, etc.). capability. Milsatcom is a system of systems that provides balanced wideband, narrowband, and protected communications ca broad range of users across diverse mission areas. The anticipated implementation of advan architectures, supported by heightened connectivity in space as well as on the ground, will e security space communications to take advantage of commercially developed Internet-like communications, but with greater assurance and security. For wideband communication needs, the Wideband Gapfiller Satellite program and the Adva Wideband System will augment and eventually replace the Defense Satellite Communication (DSCS). These satellites will transmit several gigabits of data per second—up to ten times th the satellites being replaced. Protected communications will be addressed by a global extrem frequency (EHF) system, composed of the Advanced Extremely High Frequency System an Polar System. These systems are expected to provide about ten times the capacity of curren satellites (the Milstar satellites). Narrowband needs are supported by the UFO (Ultrahigh-fre On) constellation, which will be replaced by a component of the Advanced Narrowband Syst Milsatcom Timeline). Capacity gains in these systems will also be matched by improved features, such as multiple beams that are particularly important for small terminal and mobile users. Satellite, terminal, planning segments will utilize emerging technology to ensure the best capability for the cost among ground, air, and space segments and between government and commercial assets w deployment of the most efficient, effective, and affordable communications systems. Wideband Communications Assured capacity is the primary goal of the milit communications sector. Wideband data rates a those greater than 64 kilobits per second, althou between wideband and narrowband is blurring a data rates to disadvantaged users move higher wideband requirements are currently supported the Global Broadcast Service, as well as comm These military systems, together with the plann Gapfiller satellites, will form the Interim Wideban which will eventually give way to the Advanced System. Wideband Gapfiller Satellites The Wideband Gapfiller Satellite program will p generation of wideband communications for the Defense (DOD). The constellation will suppleme X-band (roughly 7–8 gigahertz) communications The Wideband Gapfiller provided by the Defense Satellite Communicatio Satellite program will provide and the military Ka-band (about 20–21 gigahert the next generation of gigahertz up) capability of the Global Broadcast wideband communications for addition, the Wideband Gapfiller Satellite progra the Department of Defense. a high-capacity two-way Ka-band capability to s (Boeing Satellite Systems) and tactical personnel. The name "Gapfiller" is somewhat misleading b very capable wideband communication payload will include state-of-the-art technology and p leap in capability. Preliminary estimates indicate that one Wideband Gapfiller spacecraft will transmission capacity up to 2.4 gigabits per second. This capability alone exceeds the capac existing DSCS and Global Broadcast Service constellations. Throughput capacity is divided among nine X-band beams and ten Ka-band beams. Eight of beams are formed by separate transmitting and receiving phased-array antennas, which pro to shape and scale coverage areas. The ninth X-band beam provides Earth coverage. The t beams are formed by gimbaled dish antennas and include three beams with reversible polar (Polarization—the direction of the electric field of an antenna—plays an important part in opt reception or reducing the effects of jamming). The military satellite communications framework is a system of systems that provides connec range of users across diverse mission areas. In the future the framework will support "networ through an architecture that promotes the interconnection of satellites and constellations in sp through ground nodes. The key to the very flexible payload is the digital channelizer (or digital signal processor). Th divides the communications capacity into 1872 subchannels of 2.6 megahertz each and swit routes these subchannels. The signals can be cross-banded from one frequency band to an uplink coverage can be connected to any downlink coverage. Also, any uplink signal within o area can be connected to any or all downlink coverages. The implementation plan calls for a minimum of three geosynchronous spacecraft and assoc control software, with an option for up to three additional spacecraft. The payload will be inte commercial spacecraft bus. Each satellite will weigh approximately 5900 kilograms at launch than 10,000 watts of power. This design uses bipropellant chemical propulsion for orbit raisin ion propulsion to remove orbit eccentricity and for station keeping. The mean mission duratio spacecraft is 11.8 years. Synchronization of the various Wideband Gapfiller Satellite segments is under way, and 1700 operational wideband terminals are expected by 2010. Terminals capable of operating within several frequency bands are a fundamental piece of the wideband architecture, and a recent contract awarded to Harris Corporation for up to 200 lightweight, high-capacity quad-band Ground Multiband Terminals (GMTs) will help ensure the delivery of communications services through the Wideband Gapfiller satellites, as well as through the current DSCS, future Advanced Wideband System, and commercial satellite systems. Also, the Army's Multiband/multimode Integrated Satellite Terminal (MIST) will provide up to The Defense Satellite Communications Syst megabits-per-second capacity for mobile (DSCS) is part of the Interim Wideband Syst communications in the next decade. along with the Global Broadcast Service and Wideband Gapfiller System. (Lockheed Mar Responsibility for control of the satellites will Missiles and Space) be shared among various branches of the armed services. Network control will rely on existing worldwide ground facilities operated by the Army. Spacecraft control will be conducted by Air Force operators using the Comman System—Consolidated (CCS-C). The CCS-C is the integrated command and control system developed to support all milsatcom satellite constellations, legacy and future. It will replace t command and control functions of the Air Force Satellite Control Network. The Wideband Gapfiller Satellite contract was awarded to Boeing Satellite Systems in Janua the first satellite launch is planned for the second quarter of fiscal year 2004—just three yea contract award. Global Broadcast Service Operation Desert Storm clearly demonstrated the need for the rapid delivery of large volumes of information to users on the front lines. During Desert Storm, air- tasking orders and intelligence reports were sometimes delivered by hand due to the lack of available communications bandwidth. This concern drove the Through the Global Broadcast Service, information suc creation of the Global Broadcast video, maps, charts, weather patterns, and digital data Service in the mid-1990s. With the be transmitted to mobile users equipped with small tac advent of this service, most critical terminals. information could be transmitted in seconds. For example, a 1- megabyte air tasking order that might take up to an hour to transmit over Milstar or UFO (at 2.4 kilobits per second) could no less than a second. The ability to push megabits of data to a small terminal was made possi commercial advancements in high-power satellite transponders and direct broadcast service The first, and very successful, use of the Global Broadcast Service was in support of operati in 1996, where commercial satellites were used to broadcast military data to modified comm broadcast set-top receivers and decoders. Today, the Global Broadcast Service is provided through a