Space Communications Architecture
29 August 1996
The purpose of this document is to present the results of the Department of Defense (DoD) Space Architect's space communications architecture development effort completed on 29 August 1996. The full description of the process to develop architecture alternatives and the analysis leading to the final architecture is provided in the Space Communications Architecture Development Final Report by the Department of Defense Space Architect.
On 27 September 1995, the Under Secretary of Defense for Acquisition and Technology established the DoD Space Architect to integrate space architectures and systems, eliminate unnecessary vertical "stove-piping" of programs, achieve efficiencies in acquisition and future operations through program integration, and thereby improve space support to military operations. The Space Architect first task was to develop a communications architecture that encompassed core DoD capabilities; allied, civil, and commercial augmentation; and global broadcast capability. To accomplish this, a Space Communications Architecture Development Team (ADT) developed a candidate set of architecture alternatives from which the future direction for satellite communications capabilities was derived and presented to the Joint Space Management Board (JSMB) on 29 August 1996.
Space Communications Architecture
The future (2010-2025) space communications architecture is comprised of military and commercial systems providing communication services to DoD users needing mobility, high capacity, protection (anti-jam) of service, and survivability (anti-scintillation) of service. This architecture must provide these services in an environment that can accommodate advances in technology, variations to fiscal resources, and changes in national security policy. As a minimum, the systems comprising the future space communications architecture shall comply with the objectives listed in Table 1.
- Provide the right communications, information services driven, to the right user at the right time.
- Be fully integrated with the Defense Information Systems Network (DISN).
- Reduce the satellite communications "footprint" of terminals, radios, antennas, RF signature, people, etc.
- Be user friendly and interoperable.
Table 1. MILSATCOM Objectives|
Because today's warfighting operations are dependent upon the systems of the existing space communication architecture, the future space communications architecture must also consider how communication services transition from the current architecture to the future. To facilitate this, the future systems of the space communications architecture shall comply with the transition goals listed in Table 2.
- Ensure continuity of service through satellite replenishment, operations management, or risk trade-offs.
- Within limits of low or medium acquisition risk and acceptable funding, take significant steps towards the MILSATCOM Objectives (Table 1), with no barriers to evolution.
- Enable evolution to new warfighting visions (e.g.: Joint Vision 2010) by facilitating demonstrations and operational use.
- Accelerate on-going changes in terminal developments toward flexibility and systems efficiency.
Fully integrate space communication systems into the overall communications architecture.
- Take advantage of international cooperative opportunities.
Table 2. MILSATCOM Transition Goals|
Core DoD capabilities are provided by the military systems of the future space communications architecture; an EHF system, an X/Ka system, an UHF system, and a Polar system. The architectural requirements for the satellite, terminal, and network management components of these systems are described in the sections which follow.
Although they will provide a significant portion of the required capabilities, the commercial systems of the architecture are not described. This is primarily because significant technology and commercial satellite communication systems developments will be demonstrated over the next five to ten years. They include switched, crosslinked, and processed systems; large constellations of varied earth orbits; dynamic communications control; and low cost, low maintenance terminals. Other than complying with the architecture objectives listed in Table 1 and the transition goals listed in Table 2, no further architectural requirements are placed on commercial systems. Rather, it is an architectural requirement for the military systems to exploit as much of this commercial technology as possible, and for the DoD user to meet needs with commercial systems on a cost/benefit basis.
In addition to the structure for military and commercial systems, the architecture provides an environment in which the satellite and terminal systems can operate. This environment includes international cooperation, frequency spectrum allocation, launch, and standardization. Each of these topics is also addressed in the sections which follow.
EHF Satellite System
The capability to provide protected (anti-jam) and survivable (anti-scintillation) communication service is unique to a military system. There is no commercially available equivalent. The architectural goal of the EHF satellite system is to provide adequate protected and survivable communication service to maintain freedom of action during the deployment, maneuver, and engagement phases of military operations. The transition strategy from today's MILSTAR systems to the future EHF systems is to continue to field a processed and crosslinked EHF system, improving capability incrementally.
An acceptable approach to achieving this architectural goal and transition strategy is to "fly-out" the MILSTAR constellation through DFS-6, but plan military operations assuming a less than fully populated MILSTAR constellation of 4 satellites. There are several reason for this. The Space Architect estimates that 2005 is the earliest that a follow-on system will be developed and launched in the current fiscal environment. It is probable that the MILSTAR constellation will fall below its planned 4 satellite capability prior to 2005 due to launch or on-orbit failures. Therefore, it may be advantageous to evaluate the launch strategy and operating concepts for the remaining MILSTAR satellites in terms of the national security environment, even if the impact is a less capable MILSTAR constellation.
The initial capability increment in the future EHF systems should be to increase the single channel protected data rate to 6-8 megabits-per-second (Mbps) using the existing MILSTAR medium data rate (MDR) waveform. This capability should be designed to allow backward compatibility with MILSTAR II, while making an incremental step toward a single channel protected service capacity of 10's of Mbps using a waveform that is inoperable with the space communications capability provided by the other systems of the architecture, especially those system operating in the Ka spectrum.
There are many EHF system configurations that can meet the functional requirements for protected and survivability, and achieve the architectural goals and transition strategy approved by the JSMB. When approved, these alternatives shall be incorporated into the architecture.
X/Ka Satellite System
The future architecture shall provide high capacity communication service using military and commercial systems. The architecture supports providing core DoD high capacity service, with assured control and access, using a military owned system operating in the military Ka- and X-band. The architectural goal of the X/Ka system is to provide adequate high capacity communication service to all echelons required to support precision engagement. The transition strategy from today's Defense Space Communications System (DSCS) and the Global Broadcast System (GBS) capability on UFO to the future X/Ka system is to field a transponded "commercial-like" system to meet significant demand for high capacity communications and global broadcast. "Commercial-like" indicates that the system can be built from commercially available products, using commercial practices. Although some "protection" may be supported by terminal processing and the use of beam steering for the Ka frequency, there is no intent to depart from a "commercial-like" satellite to provide this capability.
An acceptable approach to achieving this architectural goal and transition strategy is to "fly-out" the DSCS system incorporating the service life enhancement program (SLEP) currently planned. Then an interim "commercial-like" X/Ka system is deployed to replenish DSCS or deployed earlier to expand the DoD's high capacity and global broadcast capability.
The DoD should consider operational management in a less than fully capable DSCS configuration of 5 satellites on-orbit. As with the MILSTAR/EHF capability, there are alternative strategies to consider when determining the launch dates of the 5 remaining DSCS satellites. First, it is probable that the DSCS constellation will fall below full performance prior to the time that constellation can be replaced with an interim X/Ka system, although a launch as early as 2003 is technically feasible. The current DSCS resources available to the DoD consists of 5 satellites yet to be launched. It may be advantageous to evaluate the timing of the launch and operating concepts of these satellites and other residual capabilities in terms of the national security environment.
The capacity of the future X/Ka system, including the capability of a single satellite, as well as the number of satellites, is dependent on the needs indicated by the national security environment, and the capabilities and cost of commercially available systems providing comparable service. The initial implementation of this system is anticipated to be transponded. While a satellite processed and switched capability offers significant capability and benefit to terminal users, the linking of this system to the commercial space communications evolution makes it prudent to observe the development of commercial systems and exploit commercial technologies when defining the future evolution of the X/Ka system. A highly desirable goal for this system is future interoperability with the other military space communications systems, including commonality of waveform with the EHF system as a minimum.
There are many X/Ka system configurations that can meet the functional requirements, and achieve the architectural goals and transition strategy approved by the JSMB. When approved, these alternatives shall be incorporated into the architecture.
UHF Satellite System
The capability to provide mobile netted communication service may be unique to a military system. There is currently no commercial equivalent; however, the planned commercial systems that are designed to provide global cellular telephone systems may, in the future, provide service equivalent to mobile netted MILSATCOM. The healthy status of the current UHF space communications systems and the anticipated near-term introduction of commercial satellite cellular hand-held telephone service creates an environment for the DoD to experiment with differing approaches to providing mobile communications service.
The architectural goal of the UHF system is to provide adequate communication service to enable dominant maneuver and information superiority. The transition strategy from today's UHF system to the future is to sustain the current UHF capability through a transition period, nominally until 2010, and decide in the 2003 to 2005 timeframe on the preferred approach to provide netted mobile and hand-held voice, paging, and low-data-rate broadcast service.
An acceptable approach to achieving this architectural goal and transition strategy is to "fly-out" the UHF Follow-on (UFO) system currently planned. If full UHF constellation capability is required to support the mobile netted communications which are an integral part of military operations, then it is necessary to launch a gap-filler UHF system to extend the UHF constellation capability until 2010. As with the EHF and X/Ka systems, operational management with a less than fully capable constellation should be planned, since the constellation may degrade below full capability prior to 2010.
There are at least four approaches that should be considered for the future mobile system. Three military systems examined by the ADT were: a cellular system at medium earth orbit (MEO); a cellular system at geosynchronous orbit (GEO); and extending a UHF capability indefinitely, but augment the wide-area mobile netted service of UHF SATCOM with non-space systems such as unmanned aerial vehicles (UAV). The ADT also considered a totally commercial configuration, since commercial space-based cellular systems will be used by DoD to meet other communication service needs.
There are other UHF system configurations that can meet the functional requirements, and achieve the architectural goals and transition strategy approved by the JSMB. When approved, these alternatives shall be incorporated into the architecture.
Polar Satellite System
In order to fulfill the military need for protected communication service, especially low probability of intercept/detection (LPI/LPD), to units operating north of 650 northern latitude, the space communications architecture includes this capability. An acceptable approach to achieving this goal is to fly a low capacity EHF system in a highly elliptical orbit (HEO), either as a hosted payload or as a "free-flyer," to provide service during a transition period, nominally 1997-2010. A single, hosted EHF payload is already planned. Providing this service 24 hrs/day requires a two satellite constellation at HEO. Beyond 2010, the LPI/LPD polar service could continue to be provided by a HEO EHF payload, or by the future UHF system - if that system is in an orbit providing polar coverage/access, or a commercial system with polar coverage/access.
There are other system configurations that can provide protected polar service. When approved, these alternatives shall be incorporated into the architecture.
The capability for warfighting forces and weapon systems to access space communication services is a critical component of the services' warfighting doctrine. The procurement plans for terminal systems reflect SATCOM capabilities at nearly all echelons. Since integration into the weapons platform is a significant portion of terminal engineering costs, the services tend to procure terminal systems by weapon platform which has led to multiple terminal types for any single satellite system. For example, a each service procures multiple UHF terminal types. The result of managing terminal procurement in this manner is a potential for higher operation and maintenance costs than if the SATCOM terminals were designed with commonality and interoperability across the space communications architecture. The ADT estimated that approximately 50% of the terminal costs, or 25% of the total space communication architecture costs, are for operation and maintenance of the terminal systems.
The architectural goal for the terminals is to provide superior information services at all command levels with reduced infrastructure. The terminal systems are the dominant factor controlling achievement of the architecture objectives (Table 1) to reduce the communications "footprint," and to fully integrate with the DISN. The transition strategy recommend by the Space Architect is to assess terminal acquisitions and designs to facilitate transition to the architecture objectives as well as the future C4ISR architecture objectives.
An acceptable approach to achieving this architectural goal and transition strategy is to provide higher data rate, protected services on mobile platforms; move toward more multi-band terminals (especially among military X, Ka, and EHF frequencies) and make every attempt to leverage commercial technology such as common printed circuit boards/components, processor controlled radios, and remotely reprogrammable systems. In addition, future terminal designs should target ease of operation and maintenance; reduce inventory of service unique, limited purpose terminals; and establish measurable goals to reduce operations and maintenance costs.
There are other approaches for terminal systems to achieve the architectural goal and transition strategy approved by the JSMB. When approved, these alternative approaches shall be incorporated into the architecture.
Network Management and Satellite Control Systems
The systems of the space communications architecture providing management of the satellite communication payloads and the dynamic control of the services provided by the space communications "network," are key to making the satellite and terminal systems inoperable and responsive to the warfighter, and making the space communications architecture integral to the overall communications architecture and the C4ISR architecture.
The architectural goal for these systems is to significantly reduce the communications "footprint." The transition strategy is to design the network management and satellite control systems to enable integration of the satellite and terminal systems with the DISN at all levels, and to ensure the systems can be adapted to provide the "right communications to the right user at the right time."
An acceptable approach to achieving this architectural goal and transition strategy is to consider the network management and satellite control systems as the integrating component of the architecture, designing it from an architectural perspective rather than as a component unique to each system. Near term steps should be taken to integrate the DISN, SATCOM and GBS nodes of the communications infrastructure. Integration of the SATCOM ground nodes would also enable better connectivity across the satellite systems (cross-banding). As the GBS design evolves, the department should implement standardized broadcast channelization so that broadcast data could be distributed on a variety of media such as protected EHF at 6 Mbps, or Ka at greater than 24Mbps, or fiber at even higher data rates, etc. The design of the network management and satellite control system must also support assessment of communication architecture, warfighting visions, and weapons system communications needs by providing the interfaces and structure to support rapid prototyping and advanced technology demonstrations. Finally, the network management and satellite control systems must be user-focused, designed to meet the C4ISR-dominance needs of the warfighter who is engaged in a dynamic and threatening battle-space.
There are many approaches for network management and satellite control systems strategy approved by the JSMB. When approved, these alternative approaches shall be incorporated into the architecture.
All of the military systems of the space communications architecture can be cooperatively developed. Cooperative development efforts offer the benefit of reducing the cost to the DoD, facilitating interoperability among coalition weapon systems, and improving global coverage and capacity of the communication services provided in the architecture. Cooperative efforts on terminals may prove to be more useful to the warfighter and economically advantageous than major programs focused on the space segments. Cooperation on international frequency spectrum allocations has significant potential impact on this latter benefit. Nearly all commercial space systems involve international cooperation through investment/ownership consortiums and international corporate partnerships. International cooperation on development of the military systems in this architecture should parallel the strategies used by commercial firms to leverage international cooperation while protecting national industry competitive interests.
International radio frequency (RF) spectrum management and allocation has significant impact on the space communication architecture. Frequency spectrum is allocated by type of communication service and physical location where RF energy can be transmitted or received. Since the frequencies allocated for space communication services today have attributes not available in other military or commercial frequency bands, and since new frequency spectrum allocations for military systems are very unlikely, it is important that the architecture efficiently and effectively use the small amount of frequency spectrum allocated. Use of the Ka-band for both commercial and military space communications services provides the greatest potential for commercial synergy through the use of COTS, for enhancement of capabilities through establishment of "CRAF-like" agreements, and for enrichment of information distribution through multi-band terminals.
Use of the Ka-band for both commercial and military space communications services provides the greatest potential for commercial synergy through the use of COTS, for enhancement of capabilities through establishment of "CRAF-like" agreements, and for enrichment of information distribution through multi-band terminals. The technical feasibility of building terminals and satellites to operate at both the military and commercial Ka-band makes it possible to plan on significant surge high-capacity capability without requiring major changes in the user's SATCOM equipment.
Because of commercial demands and EELV, launch will not be a constraint nor cost driver to the space communications architecture. Limited orbital slots and continued growth in the commercial communication market is increasing demand for heavier, higher power satellites. This demand will raise the capability well beyond that available with today's medium launch vehicles.
It is essential that the DoD remain engaged in the development of communication standards. The capability of military systems to be inoperable, nationally and internationally, is driven by standards, since common hardware and software across military and/or commercial systems is not possible. Commercial market impacts, which may create multiple proprietary standards, may warrant the need for "standardizing the standards" intended for military use. In order to achieve a seamless C4ISR environment, architecture standards addressing data management, handling, and routing; interface to fiber and terrestrial systems and weapon systems; interfaces between satellite and terminal systems; interfaces between/among satellite systems; and network management and satellite control are required as a minimum. User equipment in the architecture shall comply with the Global Command and Control System (GCCS) common operating environment (COE).