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Future U.S. Military Satellite Communication Systems

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Glen Elfers and Stephen B. Miller

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The current military satellite communications network represents decad technology. To meet the heightened demands of national security in the years, newer and more powerful systems are being developed.

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Advances in information technology are fundamentally changing the way military conflicts ar 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 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 (because of limited terminal capability, antenna size, environment, etc.).

In 1997, the Senior Warfighters' Forum established a road map cha the course of military satellite communications through 2010. In 200 there will be course corrections as the Department of Defense purs aggressive acceleration in the delivery of improved communications 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 provide the next generation of wideband communications for the Department of Defense. (Boeing Satellite Systems)

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 provided by the Defense Satellite Communicatio and the military Ka-band (about 20–21 gigahert gigahertz up) capability of the Global Broadcast addition, the Wideband Gapfiller Satellite progra a high-capacity two-way Ka-band capability to s 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 megabits-per-second capacity for mobile communications in the next decade.

The Defense Satellite Communications Syst (DSCS) is part of the Interim Wideband Syst along with the Global Broadcast Service and Wideband Gapfiller System. (Lockheed Mar Missiles and Space)

Responsibility for control of the satellites will 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, airtasking 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 1megabyte 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 series of four Ka-band transpond

steerable beams hosted on the Navy's UFO 8, 9, and 10 spacecraft. Ground terminals with a diameters of 0.6 to 1 meter receive data at rates up to 24 megabits per second per transpon of the two 500-nautical-mile diameter spot beams. Rates up to 1.5 megabits per second can through the 2000-nautical-mile diameter spot beam. Data are uplinked to the transponders t Primary Injection Points and transportable Theater Injection Points. The receiving suites and management suites supplied by Raytheon Company support military Ka-band and commerc operations. In the future, the Wideband Gapfiller Satellite will provide the Global Broadcast Service throu transponders. This is the second hosted Global Broadcast Service implementation, and its m still under consideration with regard to the Advanced Wideband System.

Advanced Wideband System The successor to the Defense Satellite Communications System and the Wideband Gapfille program is the Advanced Wideband System. The system's final configuration has not yet so ongoing milsatcom transformational efforts, but the concept is one of applied technology and that will remove capacity as a constraint on warfare communications. Analyses by the Defen Systems Agency and Joint Staff indicate that a global wideband satellite communications ca excess of 15 megabits per second will be needed by the middle of the next decade. The Advanced Wideband System will take advantage of the commercial and government technology advances of the first half of this decade to meet expected needs. Laser crosslinks, spacebased data processing and routing systems, and highly agile multibeam/phasedarray antennas will most likely be included. A constellation of advanced widebandcapable satellites is planned with a first launch at the end of this decade.

The Global Broadcast Service replaces the superhigh-frequency X payload with four 130-watt military Ka-band transponders. Each transponder can be accessed through either of the receive paths, configured by ground command. Data are transmitted through thre spot-beam antennas on each spacecraft. Two of the beams each an area 500 nautical miles in diameter, and the third covers an are 2000 nautical miles in diameter.

Capacity in the right place is the overall requirement, but getting adequate capacity to ever-smaller terminals worldwide is becoming increasingly difficult because of the limits on the amount of internatio bandwidth in the X and Ka bands for DOD use (see related article, "Critical Issues in Spectru Management for Defense Space Systems"). Several options for mitigating the current limitat consideration, including the use of higher frequencies (notably in the 40–75-gigahertz range much higher). Also, increasing the number of wideband-capable satellites over a region wou with directional antennas to use an allocated frequency band on more than one satellite in v approach would increase effective bandwidth by simultaneously reusing allocated frequencie use of small independent beams or cells, achievable through multibeam/phased-array anten Frequency reuse is an important characteristic of terrestrial and space-based cellular system frequency components with more efficiency and power will also be used to get more data to terminals, similar to the way commercial direct broadcast service transponder technology wa the Global Broadcast Service a decade earlier. Synchronization of the various Advanced Wideband System segments is beginning. To supp efforts, new terminals, such as the GMT, will be introduced, and the CCS-C will be employed significant additional capability to address the increased complexity in providing high capacit communications to highly mobile forces.

Protected Communications Protected systems have the ability to avoid, prevent, negate, or mitigate the degradation, dis unauthorized access, or exploitation of communications services by adversaries or the envir

protected systems include the Advanced Extremely High Frequency System and Advanced

Advanced EHF The loss of Milstar Flight 3 in 1999 and the last deployment of a Milstar satellite (Flight 6) in 2003 have increased the need for a successor system with full operational capability by 201 Consequently, in November 2001, the Advanced Extremely High Frequency (AEHF) System awarded to the Lockheed Martin Space Systems and TRW Space and Electronics team for t Development and Demonstration phase of the new program. Under this contract, three sate associated ground command and control segment will be produced. Under DOD transforma initiatives, other protected milsatcom options are being considered to complete the needed p strategic and tactical capability; however, if full operational capability cannot be achieved in t transformational options, then the original program to acquire four AEHF satellites plus one s restored. All new protected satellites will be interoperable with the Milstar satellites. The AEHF System will have up to 12 times the total throughput of Milstar, in some scenarios. Single-user data rates will increase from a maximum of 1.544 megabits per second (medium data rate) to 8 megabits per second (high data rate). Along with capacity, the new system will provide an almost tenfold increase in the number of spot beams for improved user access. These small beams will focus power to improve reliability and data rates to small and large terminals and to minimize interception and interference opportunities for regional adversaries. Overall, the AEHF System network will support twice as many tactical networks as Milstar. Improvements in network capability will also help ensure compatibility with international partners. As in Milstar, the AEHF System crosslinks will enhance routing and reduce vulnerability to terrestrial disruption. The new crosslinks will operate at several times the current Milstar data rate. By 2010, about 2500 terminals are expected in the protected communications inventory for the Air Force, Navy, Army, and Milstar provides protected communications a Marines. Portable, mobile, and fixed offers advanced features such as onboard s terminals with low, medium, and high data processing and satellite-to-satellite crosslink rates will support ground units, aircraft, system will eventually give way to the AEHF surface ships, and submarines. Standard system. (Lockheed Martin Space Systems. P antennas will range in size from a few by Russ Underwood) centimeters to about 3 meters. Applicable milsatcom terminals include the Family of Advanced Beyond line-of-sight Terminals (FAB-T), the Single-Channel Antijam Man-Portable Terminal (SCAMP), Secure Mobile Antija Tactical Terminal (SMART-T), and Submarine High Data Rate (Sub HDR) system. The FAB two previous programs, the Airborne Wideband Terminal and Command Post Terminal Rep establishes a family of terminals with a common open architecture for airborne and ground a For mission control, the system will have a dedicated segment consisting of communications mobile command and control centers, Satellite Ground Link Standard/Unified S-Band (SGLS control, and EHF in-band satellite control. The CCS-C will interface with the AEHF satellite c provide SGLS/USB command capabilities.

Advanced Polar S The demand for pro satellite communica support submarines other platforms and operating in the hig latitudes has steadi over the last twenty the Pentagon's Join

Requirements Over approved the Polar Requirements Docu paved the way for a address the polar c demand. Subseque decision was made series of modified E onto host satellites. package was launc and the remaining t scheduled for launc next three years. Al hosted capability wi critical service to th decade, it only mee fraction of the requi spelled out in that 1 Operational Require The Advanced Extremely High Frequency system will have Document. Conseq as much as 12 times the total throughput of Milstar, in some replacement system scenarios. Single-user data rates will increase to 8 megabits considered for the 2 per second. The system will also provide a large increase in timeframe. The Air the number of spot beams for improved user access. Command and the (Lockheed Martin Missiles and Space Systems) Joint Program Offic completed a polar c that covered 35 wid options for a future polar capability. As a result of this study, two satellites in highly inclined, molniya orbits have been recommended. In addition, transformational initiatives within the D Defense have put forward a proposed National Strategic SATCOM System that would comb and polar coverage for highly survivable communications, all in one system.

Narrowband Communications In the past, the term "narrowband" implied data rates of less than 64 kilobits per second, but boundary could apply in the future as higher data rates to small terminals become possible. other small terminal users depend on high-power, low-data-rate satellite systems to receive broadcast (as in the Navy's Fleet Broadcast) and for two-way communications. Narrowband generally transmitted in the ultrahigh-frequency (UHF) range—are supported by the UFO co which will be replaced by a component of the Advanced Narrowband System.

Advanced Narrowband System The Advanced Narrowband System is DOD's next-generation narrowband tactical satellite c system, and its goal is to provide global narrowband communications services to tactical use typically quite mobile). The Advanced Narrowband System consists of six segments: DOD s commercial space; telemetry, tracking, and command; network control; user entry; and gatew The Mobile User Objective System is the successor to the Navy's current Boeing-built UFO the key transport element in the Advanced Narrowband System. The Mobile User Objective provide beyond-line-of-sight communication to support mission objectives across all branche military. The Communications Satellite Program Office of the Space and Naval Warfare Systems Co completed concept studies resulting in several approaches to addressing narrowband needs has supported the Navy in evaluating these approaches and has collaborated, from an Adva Narrowband System perspective, on possible commercial satellite communications augmen The current UFO constellation has eight satellites, plus one on-orbit spare, each of which provides a mix of 38 UHF communication channels at 5 and 25 kilohertz and one 25-kilohertz fleet broadcast channel. About 7500 UHF terminals are in use today. The capacity of this system will fall far short of anticipated needs by the end of this decade, considering that the estimated 2010 Combined Major Theaters of War requirement is about 42 megabits per second with over 2,300 simultaneous accesses— hence, the urgent need for the Advanced Narrowband and Mobile User Objective Systems.

Launches could begin before the end of the decade, paving the way for full operational capability by 2013. The number of narrowband satellite communications terminals of all types is expected to approach 82,000 in 2010. About 50 percent of those will be handheld Combat Survivor Evader Locator units, and the remainder will be predominately legacy and advanced Joint Tactical Radio System terminals. The Mobile User Objective System will employ commercial technology to enable communications with users of large terminals and small or handheld terminals. Commercial systems such as Thuraya in the Middle East and AceS in Southeast Asia have shown that more than 10,000 low-data-rate handheld terminals can be serviced over a region with one satellite. Large multibeam antennas, some more than 12 meters in diameter, enable the use of several hundred spot beams to improve signal-to-noise levels and achieve up to 30 times frequency reuse. Systems with these capabilities currently operate at L-band (1.5 gigahertz downlink) frequencies.

The Ground Multiband Terminal is tactical satellite communications g terminal that will support operation the X, C, Ku, and military Ka band (Harris Corporation)

In addition to the Mobile User Objective System, the Navy is keeping other alternatives open Advanced Narrowband System requirements. One alternative would be to field or lease com systems, if the commercial market proves sufficiently mature. Another option would be to fie evolved UFO satellites to allow the commercial sector to mature and improve government op Navy has dubbed this alternative "UFO-E," indicating that the Navy would consider continuin constellation with gradual improvements.

Accelerating Capability In early fiscal year 2002, DOD initiated a Transformational Communications Study to accele delivery of advanced capabilities with state-of-the art technology to the field. The study is led National Security Space Architect (NSSA) and is springboarding off the NSSA's Mission Info Management Communications Architecture (see sidebar, The Space Architect). The study is increased intersystem connectivity via optical crosslinks, greater reliance on ground fiber wh and the use of commercial assets as appropriate. Potentially, all U.S. government satellite c programs in planning or development could be affected.

The Space Architect's vision of the future closely integrates government satellite communicat of systems. Additionally, it treats communications as an enterprise and balances air, space, a communications capabilities.

A large part of achieving advanced capabilities involves applying the best technology to eme programs. To ensure milsatcom's technological edge in world satellite communications, the Joint Program Office has established a Milsatcom Innovation Center to accelerate the insert

technologies into new systems. Aerospace, MITRE, MIT Lincoln Laboratory, and NASA's Je Laboratory are contributing onsite to the Center's activities. Milsatcom will most definitely ha in the future.

Further Reading 1. 2.

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5. 6.

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"Advanced Military Satellite Communications Capstone Requirements Document," H Command/J6S (April 1998). Vice Admiral A. K. Cebrowski, U.S. Navy, and J. J. Garstka, "Network-Centric Warfa and Future," Jan. 1998, http://www.usni.org/Proceedings/Articles98/PROcebrowski.h Nov. 12, 2001. W. S. Cohen, Secretary of Defense, "Information Superiority and Space," Ch. 8 in An the President and the Congress 2000, http://www.dtic.mil/execsec/adr2000/chap8.ht Nov. 12, 2001. Captain J. Loiselle, USN, R. Tarleton, Deputy Program Manager, and J. Ingerski, "Th Generation Mobile User Objective System (MUOS)," Communications Satellite Prog Space & Naval Warfare Systems Command, San Diego, CA, May 2001, http://enterprise.spawar.navy.mil/spawarpublicsite/docs/next_gen_muos.pdf, access 2001. MILSATCOM Joint Program Office Web site, http://www.losangeles.af.mil/SMC/MC, 12, 2001. H. J. Mitchell, Maj. Gen., USAF, National Security Space Architect, K. A. Johnson, C Mission Information Management Study Lead, S. S. Jenkins, Lt. Col., USAF, P. R. A USAF, MIM Study Architecture Engineers, 2000, "Architecting Information Managem Enabler for Information Superiority," http://www.dodccrp.org/2000CCRTS/cd/html/pdf_papers/Track_7/046.pdf, accessed "MUOS Fact Sheet," Navy Communications Satellite Programs, Office of Congressio Affairs, Space & Naval Warfare Systems Command, September 1999, available in th section of http://enterprise.spawar.navy.mil/spawarpublicsite, accessed Nov. 12, 200 "Report of the Commission to Assess United States National Security Space Manage Organization," January 2001, http://www.defenselink.mil/pubs/space20010111.html, 12, 2001.

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