D. A. FriTZ et al. military satellite communications: space-based communications for the global information grid David A. Fritz, Bharat T. Doshi, Andrew C. Oak, Steven D. Jones, Jack L. Burbank, Harry L. Miller, John D. Oetting, Ryan M. Collins, Lino A. Gonzalez, and Robert A. Nichols Military satellite communications (miLsATcom) systems are critical elements in DoD’s vision for a global information grid (gig). modeled after the commercial internet, the GIG will provide global connectivity to support a broad range of military user applications. commercial networking technologies, coupled with military-unique radio communications equipment, enable the GIG to support the demands of the highly mobile warfighter operating in complex radio environments. MILsATcom is divided into three categories—narrowband, wideband, and protected—matching user require- ments to suitable frequency bands. ApL is active in the development of MILsATcom systems, leveraging more than 20 years of expertise in satellite communications to ensure the global reach of the gig. THE GLOBAL INFORMATION GRID over the last decade, the Internet has enabled tre- commercial solutions to address information assurance mendous gains in business productivity via rapid global issues such as communications security, transmission information sharing, effective collaboration, and com- security, and the integration of priority and precedence munications across organizational boundaries. moti- with commercial quality of service. vated by the immense success of the Internet in the com- even with a common ip layer for networking, the mercial world, the DoD, the intelligence community, physical and link-layer technologies will vary signifi- and NAsA have collectively embarked on an ambitious cantly across the network segments that will compose effort to migrate their information systems and networks the GIG. Depending on geographical location, commu- to a common IP backbone, providing infrastructure and nications environment, user density, and other factors, application platforms for network-centric operations and each segment of the GIG will apply novel solutions to warfare. it is worth noting that, despite the intent to meet the warfighter’s requirements. The MILsATCOM leverage commercial technology, the development of the systems are excellent examples of diverse physical and global Information Grid (GIG) will inevitably require link layers, designed to address unique user require- the incorporation of military-unique features into the ments. The frequencies at which MILsATCOM systems 32 Johns hopkins ApL TechnicAL DigesT, VoLume 27, number 1 (2006) spAce-bAseD communicATions For The gig #URRENTSYSTEMS 2OADMAP 4RANSFORMATION 2OADMAP -ILSTAR !DVANCED%(& 0ARTIAL (IGHSECURITY (IGHSECURITY !%(& -ODERATEDATARATES -ODERATEDATARATES UPTO-BPS UPTO-BPS 4RANSFORMATIONAL3ATELLITES 7IDERANGEOFUSERTERMINALS 7IDERANGEOFUSERTERMINALS (IGHSECURITY $EFENSE3ATELLITE 'APFILLER (IGHDATARATES #OMMUNICATIONS3YSTEM !DVANCED7IDEBAND3YSTEM UPTOSOF-BPS 7IDERANGEOFUSERTERMINALS -EDIUMSECURITY -EDIUMSECURITY (IGHDATARATES (IGHDATARATES 'APFILLER UPTOSOF-BPS UPTOSOF-BPS -OSTLYLARGETERMINALS -OSTLYLARGETERMINALS 5(&&OLLOW ON3YSTEM -OBILE5SER/BJECTIVE3YSTEM -OBILE5SER/BJECTIVE3YSTEM ,OWSECURITY ,OWSECURITY ,OWSECURITY ,OWUSERRATES ,OWUSERRATES ,OWUSERRATES UPTOLOWSOF+BPS UPTOMID SOF+BPS UPTOMID SOF+BPS -AINLYSMALLTERMINALS -AINLYSMALLTERMINALS -AINLYSMALLTERMINALS Figure 1. Transformational Communications Study impact on the DoD MILSATCOM Roadmap. operate were chosen to best address a range of user a MILsATCOM architecture that would remove com- requirements: narrowband communications at uhF, munications as a constraint to the warfighter. wideband communications at SHF, and protected com- While the TCS Roadmap has remained unchanged munications at ehF. each of these frequency bands since 2002, the timelines and programmatics to bring provides distinctive capabilities and presents new chal- the vision to reality continue to be refined. The inte- lenges in terms of integrating with the network-centric grated system-of-systems miLsATCOM architecture vision for the GIG. for the transformation is better illustrated in Fig. 2, before 2002, the MILsATCOM Roadmap was focused which highlights the satellite systems to be deployed on a continued presence in the three primary frequency over the next 5 to 15 years. The Mobile User Objective domains (uhF, shF, ehF), representing three classes system (MUOS), Wideband gapfiller system (WGS), of users and technology. The Roadmap depicted in Fig. and Advanced ehF (AEHF) will be deployed earlier, 1 shows that, before 2002, modifications to systems in while the Transformational satellites (TsATs) and many cases were evolutionary, not revolutionary. In each the Advanced Polar System (APS) will come onboard frequency band, the Roadmap called for a new system to mostly after 2012. The low data rates of the MUOS make replace current satellites, incrementally improving per- it suitable primarily for tactical applications. The other formance through state-of-the-art technology insertion. systems can be used for tactical, strategic, and backbone in January 2002, the DoD initiated the Transforma- applications. Together, these systems represent a major tional Communications Study (TCS) to consider ways commitment to miLsATCOM and to realizing the to revolutionize MILsATCOM systems. One TCS goal GIG vision. was to create a high-capacity IP backbone in space. As An additional challenge in achieving this vision is to a result, the post-2002 TCS Roadmap sought to consoli- interconnect these satellite systems to ground- and air- date functionality across the previously separate wide- based tactical networks and to high-capacity wireline band and protected satellite systems and, through the backbones like the gig bandwidth expansion (GIG- application of advanced optical technology, to achieve BE) fiber-optic network. A large part of this challenge AEHF APS IC backbone WGS (3 GEO) MUOS TSATs (5 GEO; X- and . (4 GEO) . Ka-band) (5 GEO) . RF Laser GIG-BE/teleport connectivity Joint Tactical Radio System/ wireless connectivity Figure 2. MILSATCOM system of systems (GEO = geosynchronous Earth-orbit satellites). Johns hopkins ApL TechnicAL DigesT, VoLume 27, number 1 (2006) 33 D. A. FriTZ et al. is being addressed by the DoD Teleport Program. This satellite was launched in 1993, and the constellation was program is aimed at allowing true multiband capabil- completed with the launch of UFo Flight 11 in Decem- ity so that different satellite systems as well as different ber 2003. ground-based systems can interoperate by connecting at because narrowband SATCOM can support a wide one of the global Teleport sites. Although initial deploy- variety of applications, the UFo system and its predeces- ment of Teleport provides only circuit connectivity, a sors have been consistently oversubscribed. To mitigate future generation will have ip capabilities consistent this problem, DoD has developed multiple access pro- with the vision for the GIG. tocols to allow a single UHF SATCOM channel to be The following sections briefly describe the MILsAT- shared by many applications. These protocols use time- COM systems, the Teleport Program, and ApL’s involve- division multiple-access schemes, with access granted ment in the integration of these network segments to either on demand or according to a predetermined create the GIG. plan. While these protocols do allow wider access to uhF SATCOM resources, the consistent and sustained NARROWBAND SATCOM growth in demand for such access since the first Gulf War continues to leave the system oversubscribed. DoD’s narrowband SATCOM systems yield low-data- The ongoing development and evolution of the rate (less than 64 kbps), beyond-line-of-sight (bLOS) DoD Teleport program (discussed later in this article) communications. These systems have been designed will give the uFo user access to the gig and some with the mobile, tactical warfighter in mind. This is Defense Information Services Network (DISN) services. apparent in the satellite constellation design and fre- Although access will be somewhat limited in terms of quencies of operation as well as the system’s support of dynamic accesses and the number of DISN services pro- relatively simple, low-cost, mobile terminals. vided, this is an important first step in bringing the GIG These narrowband systems are designed to operate to the mobile tactical user. in the UHF band (290–320 MHz uplink and 240–270 MHz downlink). systems operating in this band are The Mobile User Objective System better able to penetrate foliage and atmospheric condi- MUOS is currently under development as an even- tions such as clouds, rain, or fog. UHF SATCOM termi- tual replacement for the uFo system. To meet future nal antennas have relatively broad beamwidths, which MILsATCOM requirements, it has become apparent allows the mobile user to communicate even if terminal that dramatic improvement is needed in some areas, antenna pointing is imprecise. UHF SATCOM is pro- such as capacity and support of communications on the vided by geosynchronous satellites, enabling worldwide move (COTm). While DoD’s narrowband sATCOM coverage up to approximately ±70º latitude. Therefore, systems have always supported mobile platforms, the it can be seen that the UHF SATCOM systems were military’s conception of coTm has evolved signifi- designed to enable bLOS communications anywhere, cantly over time. For example, over the past 30 years, anytime. the concept