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Executive Summary Major changes in recently announced naval missions and strategy emphasize the need for comprehensive command, control, and communications (C3) capabilities to support naval forces that are deployed globally and that are ready to project power ashore as part of a joint U.S. military force. Under this new doctrine, the Naval Force Commander requires these new capabilities either to command a joint task force or to host a joint task force commander, as well as to conduct assigned missions as part of that task force. The Space Panel of the Naval Studies Board was asked by the Chief of Naval Operations to examine two areas relating to this new strategy. The first concerned the use of space and airborne systems in the surveillance, detection, identification, targeting, and battle damage assessment of a generic target set (including critical mobile targets) expected in regional conflicts. The second concerned the definition of a new space-based communications architecture to support a wide variety of naval tactical operations anticipated in a regional conflict environment. This report describes the panel's work to define a space-based naval communications architecture. The effort involved a review of existing naval communications requirements as well as the definition of new requirements based on several postulated tactical situations involving precision strike operations. These requirements were characterized at the global, theater, regional, and tactical levels in terms of coverage, type of service, threat protection level (or robustness), timeliness to initiate the service, and capacity. The results show that global coverage will continue to be needed well into the foreseeable future and that the need is particularly significant in the mid-latitudes. A wide range of communications services are required, depending on the specific level of command. These services are required for both fixed and mobile users and include voice, data, facsimile, video, and image transmission, with data rates extending from less than 10 kilobits per second (kbps) to upward of several hundred megabits per second (Mbps), again depending on the specific user and purpose. The degree of protection afforded these links ranged from "hard core" (high levels of antijam, intercept, and scintillation protection), through "soft core" (moderate levels of antijam and intercept protection), to "general purpose" (minimal protection). The panel concludes that naval communications have to be interoperable with joint service, allied, and selected coalition force systems and observes that this could be achieved most effectively through the use of waveform, frequency assignment, and communications protocol standards in most cases, and with common equipment in selected cases. The panel recommends that these requirements be incorporated into future Navy satellite communications requirements documentation. The study reviewed current and planned military, civil, and commercial satellite communications capabilities, and the panel concludes that selected combinations of these systems (using existing technology) could meet most identified requirements. Current Navy communications is highly structured, with little flexibility to dynamically shift or reconfigure resources. Also, the current systems have limited throughput capacity and are vulnerable to unintentional, as well as intentional, interference, and jamming. The panel observes, however, that the Navy has strong programs in the ultra-high frequency (UHF) and extremely high 1

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frequency (EHF) bands, in terms of on-orbit and planned satellites and terminal development efforts. Also, recent efforts have been made to improve throughput capacity by making greater use of super-high frequency (SHF) systems on its principal command (Tomahawk-capable) ships. The Navy currently makes only limited use of commercial satellite communications service. Large-scale use of this service by the Navy requires careful consideration of several factors, including (1) coverage—commercial systems provide only limited oceanic coverage and are driven more by the market potential over landmasses, (2) frequency assignments and compatibility with existing Navy terminals, (3) shipboard electromagnetic interference from local high-power transmitters, (4) throughput capacity available to military users, (5) cost of service, and (6) treaty restrictions on military use. In defining a "goal" naval communications architecture, the panel concludes that this architecture, designated NAVSATCOM-21, should consist of a multilayered hierarchical structure of interconnecting networks that are geographically dispersed and employ differing topographies (i.e., mesh and hub-spoke) that allow point-to-point and broadcast services to network users. The architecture should include a global, high-capacity backbone network using optical fiber technology to achieve data throughput greater than 1 gigabit per second (Gbps), with both fixed and mobile gateways to selected task force elements and tactical units. High- capacity (several Mbps) tactical networks should provide connectivity among selected platforms and command nodes utilizing satellite communications relay, as appropriate, and these should interface directly to shipboard local area networks. The architecture should permit dynamic network management and control, and rapid configuration. For those connectivities of the architecture requiring high throughput capacity (>2.4 kbps) to some fixed, but predominately mobile, users at over-the-horizon distances, the links should be implemented using integrated UHF, EHF, and SHF military satellite communications capabilities, heavily augmented by commercial systems where practicable. Figure ES. 1 provides an overview of the principal elements of NAVSATCOM-21. The panel recommends that the Navy maintain and reinforce continued investment in EHF as the principal hard-core and soft-core satellite communications resource and utilize UHF and commercial to support general-purpose requirements. Also, the Navy should consider adding a medium-data-rate (MDR) capability to existing low-data-rate (LDR) EHF terminals and investigate the feasibility (in terms of cost, schedule, and technical risk) of an MDR engineering change to the UHF Follow-On satellites. The Navy should continue its efforts at SHF as an interim soft-core capability (particularly the demand assign multiple access (DAMA) program) to increase the use of available SHF channel capacity—especially on the Defense Satellite Communications System (DSCS). Also recommended is Navy investment in development of a low-cost multifrequency (C-, X-, and Ku-bands) shipboard terminal for increased access to services at SHF. Particularly important to this multifrequency terminal is a suitable antenna system. The panel endorses Navy efforts to develop a multimission, multi-user broadband antenna (MMBA) to achieve a more robust SHF capability with minimal space and weight requirements. The panel acknowledges the Navy's expansive use of UHF as a general-purpose service and recommends that the throughput capacity of these systems be increased tenfold through the use of more efficient modems and modern modulation techniques, such as constant envelope, multiphase, trellis-coded approaches.

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SHF UHF EHF SATELLITES • EHF: MILSTAR/MILSTAR II UFO PACKAGES AUGMENTATION: POLAR, ETC • UHF: FLTSAT, UFO •SHF: DSCS, ALLIED •COMMERCIAL COMMERCIAL CONNECTIVITY TO AIRBORNE PLATFORMS •HARD/SOFTCORE; EHF • INTERIM SOFT CORE; SHF - POSSIBILITY FOR LONG TERM BACKUP VIA MULTf- BANO TERMINAL • GENERAL PURPOSE UHF COMMERCIAL •LDR: UHF OR EHF •MDR: EHF •HDR/VHDR: MODIFIED EHF OR Ku BAND (TDRSS) ALL LINKS CONFORM TO INTEROPERABILITY STANDARDS ALL NODES WITH FULLY INTEGRATED GPS | MOBILI ERMINAL TYPES _ - MULTI-BAND SHF - COMMERCIAL FIGURE ES.l NAVSATCOM-21 overview. The panel concludes that expanded use of the Global Positioning System (GPS) in all communications nodes is a straightforward way to improve control and operation of all Navy satellite communications in terms of more accurate positional knowledge (especially for mobile users) and timing synchronization, and recommends its full integration into these nodes as soon as possible. Finally, the panel concludes that a robust satellite communications capability, as highlighted by the NAVSATCOM-21 architecture, could have a significant impact on the effectiveness of all expanded Naval Expeditionary Force missions, especially precision strike

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operations. Figure ES.2 summarizes the key features of NAVSATCOM-21 and relates the capabilities to conduct these operations today to those that would be enabled if the architecture were to be fully developed. The panel recommends that NAVSATCOM-21 be implemented in a time-phased manner in conjunction with ongoing Department of Defense (DOD) and commercial satellite communications development efforts, and through existing and planned Navy communications programs, including the Copernicus architecture effort, Communications Support System (CSS) effort, and advanced multifrequency terminal and antenna development efforts. NAVSATCOM-21 GOAL ARCHITECTURE I OPERATIONS \ \ TODAY ) I OPERATIONS \ \ ENABLED ) A) ADAPTABLE GLOBAL COMMUNICATIONS NETWORK B) MDR INTEROPERABLE BACKBONE C) GATEWAYS TO INTERCONNECT BACKBONE TO WANs D) AUTOMATED AND DYNAMIC NETWORK MANAGEMENT OF DISTRIBUTED SYSTEMS E) SMALL TERMINALS FOR AC AND CMS F) INTEGRATION OF GPS INTO ALL PLATFORM SYSTEMS G) TRANSPARENT TO DATA OR OTHER USER TRANSPORT • BATTLE SPACE = 300 MILES • CM RXED TARGET AREA AND FLIGHT PRORLE AT LAUNCH • LOS RECONNAISSANCE FOR CM-BDA • LIMITED JOINT AND ALLIED COMMUNICATIONS • INDEPENDENT DATA BASES • COMMAND VOICE CONFERENCING > SPECIALIZED LPl/AJ CAPABILITY • UNIT LEVEL OPERATIONAL TRAINING • BATTLE SPACE EXPANSION TO 1000+ MILES - FLEXIBLE IN-FLIGHT ATTACK OPTIONS • REALTIME BLOS BDA FOR CM RETARGETING • EXPANDED INTEROPERABILITY • RAPID DATA SHARING FOR BATTLERELD AWARENESS • COMMAND VIDEO CONFERENCING > ENHANCED LPl/AJ • INTEGRATED OPERATIONAL TRAINING AMONG OWN, JOINT AND ALLIED UNITS FIGURE ES.2 NAVSATCOM-21 key features summary and their impact on future naval operations. (The letters in the arrows identify the specific architectural feature(s) that affect the operations capability.)