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Navy’s Needs in Space for Providing Future Capabilities 4 Implementation: Navy Support to Space Mission Areas Naval forces have continued to be major users of information derived from space-based systems of all types. In order to help identify the Navy’s needs in space for providing future capabilities, the committee reviewed the Navy’s participation and needs with respect to current, planned, and proposed space-based capabilities that may have an impact on the successful implementation of Sea Power 21 warfighting concepts. Specifically, the committee’s review is structured around these space-based capabilities and the six National Security Space (NSS) mission areas: intelligence, surveillance, and reconnaissance (ISR); meteorology and oceanography (METOC); theater and ballistic missile defense (TBMD); communications; position, navigation, and timing (PNT); and space control. Table 4.1 provides a status of several current, planned, and proposed space-based capabilities, from which one can conclude that the Navy needs to collaborate with a significant variety of agencies outside the Navy in order to ensure that its Navy-unique needs are satisfied. Thus, the Navy’s participation in the development of space systems needs to be flexible in order to meet the needs of a variety of partner agencies as well as to enable effective leadership of the Navy’s own programs and initiatives. The sections below detail the Navy’s current participation across each of the space mission areas and also provide an assessment of how the Navy can improve its use of these systems and better influence the development of new systems, thus ensuring that its needs in space will be met in the future.
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Navy’s Needs in Space for Providing Future Capabilities INTELLIGENCE, SURVEILLANCE, AND RECONNAISSANCE The Navy has recently been moving toward the adoption of Sea Power 21 as a global instead of a regional strategy, but a strategy that still addresses regional and transnational threats. These threats are unlikely to be concentrated in a few regions that can be simultaneously addressed using concentrated forces. Instead, the National Security Strategy states that it will be necessary to address threats anywhere on the globe, and at a tempo that will permit dealing with many, widely dispersed threats quickly, decisively, and nearly simultaneously.1 This calls for forces to operate using the most exact information possible about the enemy, to analyze that information to determine critical nodes to attack, and to direct weapons systems, launched from widely dispersed platforms, to strike those nodes. The role of the Navy in such a strategy is especially important, given its traditional forward presence, sea dominance, and strategic sealift. In this role, the Navy capitalizes on and builds from NSS and organic Navy ISR capabilities to support broad coverage and over-the-horizon (OTH) targeting, followed by precision strike using precision-guided munitions (PGMs). The capabilities of the individual Sea Power 21 pillars—Sea Strike, Sea Shield, and Sea Basing—are all, to varying degrees, dependent on ISR involving data from space-based, airborne, ground-based, and sea-based sensors. These capabilities are also central to the realization of the FORCEnet foundation that enables the operational implementation of Sea Power 21. NSS systems have proven invaluable for both complementing and expanding the ISR capabilities provided from other sources. ISR information from NSS sensors is merged with ground-, sea-, and air-based sensor data to develop fused products to assist in the positioning and repositioning of platforms and forces; to identify and assault critical vulnerabilities and centers of gravity of enemy forces; to assess damage; and to permit the efficient use of resources to conduct concurrent and follow-on missions. Furthermore, NSS support is used to deter enemies from employing an effective threat to U.S. strike operations by maintaining surveillance capability against potential conventional as well as unconventional strikes. NSS ISR capabilities could become significantly more important to the Navy if, in the future, near-real-time persistence from NSS ISR systems was achieved. For space systems, persistence is achieved by increasing either the period of observation by sensors on a particular satellite (for instance, geosynchronous satellites can continuously observe one-half of Earth at a time) or by increasing the number of satellites carrying the particular sensors (for instance the Global Positioning System (GPS) uses a constellation of 24 satellites to enable continuous ground observation of at least 4 GPS satellites). 1 President George W. Bush. 2002. The National Security Strategy of the United States of America, The White House, Washington, D.C., September 17.
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Navy’s Needs in Space for Providing Future Capabilities TABLE 4.1 Status of Current, Planned, and Proposed Department of Defense Space Systems Programs Including General System Limitations and Risk Space-Based Capability Current Programs Available? Imagery (infrared, visible, radar) NRO systems, FIA, SBR commercial imagery Yes Electronic intelligence (ELINT) NRO systems Yes Navigation GPS Yes Timing GPS Yes Meteorology and oceanography GOES, POES, NPOESS Yes Ground moving target indication SBR No Airborne moving target indication None No Boost-phase missile defense SBIRS-H No Midcourse missile defense SBIRS-L No Space-based IP networks (GIG) TCA No Satellite communications MUOS, MILSTAR, AEHF, commercial Yes NOTE: A list of acronyms is provided in Appendix G. The primary constraint on ISR satellites is related to simple physics: orbits enabling long duration over a spot on Earth require high-altitude orbits—but the higher the orbit, the lower the fundamental resolution of any orbital imaging system. Thus, high-resolution space imaging systems require a large number of less-expensive, low-Earth-orbit satellites, or a smaller number of medium-Earth-orbit or geostationary-Earth-orbit satellites carrying extremely expensive high-resolution imaging systems. Recently, several novel schemes have been proposed for using fleets of microsatellites linked as an interferometric array, thus providing high resolution with small identical satellites. Such proposals are in the very
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Navy’s Needs in Space for Providing Future Capabilities Oversight Agency General Limitations Status/Risk DOD Executive Agent for Space, NRO, NGA Satellite revisit time FIA and SBR in development, SAR versus GMTI trade-offs for SBR DOD Executive Agent for Space/NRO Encryption, geolocation accuracy Gap-filler satellite may fill need Air Force Vulnerability to countermeasures Enhanced jamming protection programmed Air Force/Navy Few Ongoing clock development NOAA Passive sensors only, resolution and revisit times, international partnerships Cost, feasibility of active sensors Air Force Revisit time, field of view, data rates R&D issues, cost, trade-offs between SAR and GMTI, ubiquitous coverage None designated Stressing technology, data rates Ubiquitous coverage, use of space sensor for weapon guidance MDA Stressing technology Cost, technical risk, system under development MDA Stressing technology Cost, technical risk, no current program DOD Executive Agent for Space Wideband laser links Development risk, cost, system under development Air Force and Navy Data assurance, link availability Bandwidth demands growing rapidly early development stage and might represent a novel route for additional science and technology (S&T) support. Combining improved persistent NSS ISR capability with improved communications, processing, and exploitation systems will enhance the ability of the Navy to engage in future missions (provided that the capabilities are developed in accordance with naval needs). One additional factor (discussed in the major section below entitled “Space-Based Communications”) is the need not only for timely acquisition of ISR information, but also for its timely analysis and dissemination. This need has recently been embodied by the Department of Defense (DOD) in the information
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Navy’s Needs in Space for Providing Future Capabilities dissemination concept known as TPPU, or “task, post, process, and use.” Under TPPU, all ISR data are to be made immediately available (posted) for processing and use by any potential end user. This concept has the goal of making ISR data available for use more quickly than has been possible in the past. However, under TPPU large volumes of unprocessed (raw) ISR data will be regularly transmitted to end users, and the committee is concerned that TPPU may significantly increase the communications bandwidth needed to effectively access and utilize the ISR data. Future Space-Based Intelligence, Surveillance, and Reconnaissance Systems Historically, NSS ISR systems have been managed by the National Reconnaissance Office (NRO) and have significantly improved the effectiveness of naval missions. The Navy has been a major participant in these NRO programs to ensure that naval interests are served. While these past and current NSS ISR systems and augmentations have proven their value, NSS systems currently in the development and/or planning stage by the NRO and the Air Force hold promise of even more improvements in naval capability. Two systems in particular are noteworthy in this regard: The Future Imagery Architecture (FIA) being developed by the NRO, and The proposed Space Based Radar (SBR) being planned by the Air Force. FIA is being planned to replace the NRO’s existing series of national optical and infrared imaging satellites. While the details of the program are largely classified, the FIA initiative will represent a significant improvement to the nation’s space-based imagery systems, in terms of both resolution and persistence. The Navy needs to remain engaged in this initiative to ensure that its maritime imagery needs will be met by FIA. SBR represents a plan to field a space-based radar to enable near-continuous monitoring (through either radar imagery or ground moving target indication (GMTI)) of the majority of Earth’s surface—a critical supporting capability to enable the Navy to provide maritime domain awareness consistent with its role in homeland defense. SBR is such a major ISR initiative that the United States is unlikely to support an alternative space-based radar initiative in the next several decades. Thus, it is imperative that the Navy understand its needs for this extended time period in order to be able to ensure that its needs will be met by SBR. While the capability assessment for NSS ISR (summarized in the tables in Appendix C) is based on what could be provided with a nominal SBR, the committee believes that the Navy has not yet interacted with the SBR program office on the scale required to assure that Navy requirements will ultimately be met. The few individuals currently representing the Navy’s interests in SBR have made signifi-
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Navy’s Needs in Space for Providing Future Capabilities cant progress toward inserting Navy requirements into the SBR planning process. These inputs, however, appear to have been based on limited background analyses. The Navy is developing an understanding of the operational implications of the various modes and capabilities of SBR against future naval scenarios. The Air Force has agreed to conduct some simulations involving near-term maritime scenarios, but SBR also needs to be integrated into maritime modeling and simulations looking over the several decades that SBR would be in existence. As discussed elsewhere in this report,2 the Navy currently lacks a modeling and simulation effort to support thorough operations analysis that can permit cost-benefit and performance trade-offs across a wide range of systems (including SBR) against the needs arising from a wide range of future naval scenarios. Without full and traceable analysis of the requirements for supporting Sea Power 21, including a good understanding of the related technical issues, the committee is concerned that SBR may not meet some of the Navy’s key performance and operational requirements. Because there has been little Navy S&T funding for SBR, there has, to this point, been an incomplete understanding of numerous aspects of how a maritime SBR could be designed differently from the current SBR baseline. To overcome some of these deficiencies, the Navy recently funded the Naval Research Laboratory (NRL) to identify new SBR modes of operation that can support maritime operations. As of early December 2003, the Air Force had accepted some of these options into the SBR baseline. In this case, the Navy was able to leverage its internal S&T experience to help define the technical features of the SBR needed by the naval forces. The committee encourages further similar Navy involvement. The FIA and SBR programs will provide improved capability for monitoring fixed targets and threats (both FIA and SBR) and moving targets and threats (SBR). Following is an assessment of how existing and planned NSS ISR systems enable the capability areas identified by Sea Power 21. The resulting Sea Power 21 capability dependencies are summarized in Appendix C. Sea Power 21 Capabilities Sea Strike Through Sea Strike operations, naval forces will execute and direct decisive and sustained influence in joint campaigns. Sea Strike relies on a combination of ISR assets—space-based, theater, and force—to support the conduct of the following types of operations: 2 See the section entitled “Navy Space Support” in Chapter 3.
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Navy’s Needs in Space for Providing Future Capabilities Strike operations against fixed and moving targets on land and on sea, Special operations that require precision targeting information, and Defensive operations necessary to ensure strike aircraft survivability. Today, strike targets are identified, classified, tracked, and geolocated through a combination of sensors on NSS systems, airborne platforms, and naval platforms. NSS and airborne systems are generally used cooperatively to support time-sensitive requirements of strikes. The requirements of the Navy for overland targeting are essentially identical to those of the other Services; however, the Navy will need to carefully manage and guide the course of progress on its requirements for over-water targeting to ensure that they are included in future programs. In particular, many satellite systems do not operate over the open ocean (this includes early plans for the SBR described above)—pointing out the Navy’s need to track even its most basic requirements on availability. During a system’s development and operational phases, technical and funding support is typically needed to improve performance and adapt the system to changing threat and target conditions. Additionally, the Navy will need to explore the potential of other new space ISR capabilities, such as hyperspectral imaging to assist in separating targets from background and camouflage, especially in the open-ocean and littoral areas unique to the operations of Navy and Marine Corps forces. In general, the future FIA and SBR systems could greatly enhance NSS support for Sea Strike by— Improving persistence through increased numbers of satellites, and Improving image resolution, thereby strengthening the ability of naval forces to identify, track, and target terrorist and other small-unit threats. Sea Shield To maintain littoral superiority for naval and joint force components, ISR resources must be able to support protection against conventional and unconventional (i.e., chemical, biological, radiological, nuclear, and environmental) threats from special operations and terrorist forces. Information from space-, ground-, and sea-based and airborne ISR resources need to be used, where possible, to identify and locate near-horizon and over-the-horizon threats, to enable afloat operations by supporting self-defense against and/or neutralization of undersea threats (including those from submarines, mines, submerged barriers, and obstacles), and to provide defense over land and over sea against theater air and ballistic missile threats. The support of all of these defensive operations currently challenges NSS ISR resources and will continue to do so for the foreseeable future. One of the limitations of current NSS systems in contributing significantly to defensive antisubmarine warfare (ASW) and countermine operations is the lack
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Navy’s Needs in Space for Providing Future Capabilities of persistence in making observations of offensive enemy operations. It is possible to observe enemy submarines at shallow depth from space, and also to observe the laying of mine fields or the navigation by enemy combatants through mine fields they have laid. However, the long time lapses between overhead satellite observations by current NSS systems do not support the near-continuous observations needed.3 As described above, the future FIA and SBR systems, if fielded, should significantly improve overall observational persistence. Today, most operations rely largely on theater assets (the SPY-1D radar system on the Navy’s Aegis ships, sensors on E-2C and E-3 aircraft, and so on) to provide the ISR information necessary to support Sea Shield operations effectively. For surface warfare, Sea Shield requires that ISR capability provide near-horizon and over-the-horizon warning, tracking, and targeting information against surface targets; these requirements are similar in many regards to the Sea Strike capability needs. In addition to the improvements noted above that would enhance NSS support for Sea Strike, the future FIA and SBR systems should greatly improve NSS support for Sea Shield by— Increasing coverage areas, thereby extending the engagement distance to distances beyond the threat range from enemy combatants; and Establishing a space-based GMTI capability (with SBR), thereby enabling space-based, near-continuous tracking of moving surface vessels. Similarly, undersea warfare support can be extended in area by improved persistence of SBR and FIA, provided that these systems are designed and operated specifically to address the special needs of large-area search in ocean areas. These forms of support are just the beginning, however, and long-term S&T is needed in support of effective naval specification and use of SBR. As an example, further S&T funding could be provided to support a comparison of the expected performance of radars with which the Navy is familiar (such as the E-2C aircraft radar and its upgrades) with the various options for SBR. Such analysis would help establish and maintain the connection between specialized maritime radar experts, the operational Navy, and the SBR office. Sea Basing Sea Basing entails the provision of the full capabilities of an at-sea joint command center as well as the provision of all of the associated sea-based logis- 3 The Office of Naval Research has developed, under its littoral remote sensing effort, a series of automated analysis algorithms for using data from the nation’s space-based intelligence assets to assist with nearshore mine and mine field detection from the surf zone on to the beach. These algorithms have transitioned, via the organic mine countermeasures Future Naval Capabilities program, to the Naval Oceanographic Office Warfighting Center. Fleet awareness and use of these algorithms are continuing issues.
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Navy’s Needs in Space for Providing Future Capabilities tics needed for initial surface and amphibious strike actions. Thus, the ISR needs for Sea Basing are covered primarily by providing access to the capabilities needed to support Sea Strike and Sea Shield. The additional capabilities needed for Sea Basing are primarily structured around logistics support needs (primarily for optimal ship route planning) and are described in the next major section, “Meteorology and Oceanography.” FORCEnet Force projection and defense from forward-deployed Navy platforms depend on the efficient networking of naval, national, and joint nodes involved in all aspects of information production, command responsibility, and control authority through communications and computing power to meet Navy objectives. These topics are broadly included under the heading of FORCEnet. ISR derived from NSS sensors is an important portion of FORCEnet, and the information from these NSS sources will be used in conjunction with information gathered from other sources to support overall Navy objectives. In reality, most strike actions and most projections of defensive capability will cooperatively use information from multiple ISR sources to engage targets and threats, and the actual source of any individual information element will be transparent to the warrior. The timeliness, relevance, quality, and quantity of the information, however, will continue to determine the outcomes of naval missions. As the mission of the Navy grows in the 21st century and as the theater of importance expands to global dimensions, the importance of access to global, persistent ISR information will necessarily grow. In other words, as the need for technology associated with space grows, the technology associated with the analysis, exploitation, and fusion of NSS-derived data will also need continued improvement. In summary, then, it is unlikely that the Navy will be able to meet its overall Sea Power 21 ISR needs without a strong program of S&T, space engineering, and program participation involving naval and Navy-sponsored personnel. These efforts will also require a continuing commitment of personnel and funding to NSS ISR activities. Capability Shortfalls and Technology Gaps of National Security Space Intelligence, Surveillance, and Reconnaissance Systems for Navy Use Given the needs discussed above for ISR support from space, there are several shortfalls and gaps in current and currently planned NSS ISR capability that will limit the Navy in carrying out the elements of Sea Power 21 effectively. These are summarized in Table 4.2. The approaches that the Navy has available to it to address the shortfalls and gaps listed in Table 4.2 fall into four general areas:
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Navy’s Needs in Space for Providing Future Capabilities TABLE 4.2 Shortcomings of National Security Space (NSS) Intelligence, Surveillance, and Reconnaissance (ISR) Systems for Navy Use NSS ISR Shortcoming or Gap for Navy Use Navy Issues Persistence Long revisit gaps between images, no long dwell sensors, too few satellites, and no moving target indication (MTI) radars. Space Based Radar (SBR) and Future Imagery Architecture (FIA) may alleviate gap. Area coverage Operation of satellites over ocean, resolution versus coverage, synthetic aperture radar versus MTI look angles. SBR and FIA may alleviate gap. Ocean operations Operation over oceans, operating modes to counter effects of ocean clutter. SBR and FIA may alleviate gap. Supporting S&T to address the NSS ISR shortfalls and gaps and then transitioning the results of this S&T work into planned and ongoing NSS programs. This approach requires a knowledgeable space cadre that understands both space technology and the operations of naval forces. To date, the Navy has used such an approach effectively in many programs for which the NRO or the Navy itself has been the lead agency. Key to this success has been the Navy’s Technical Exploitation of National Capabilities Program (Navy-TENCAP), which is specifically designed to provide a link between existing national capabilities, naval operations, and fleet experiments. The Navy can benefit from a similar program aimed to experiment with Air Force programs. Directly participating in programs that can mitigate these NSS ISR shortfalls during the course of the programs’ evolution. The involvement of the space cadre in these programs needs to be carefully coordinated, and billets might sometimes need to be accompanied by modest Navy dollars to provide the leverage necessary to support Navy direction and to promote changes sought by the Navy. Again, the Navy has used this type of approach well in programs with the NRO, and it would be well served to expand this level of participation into most Air Force programs. Providing significant Navy dollars to relevant space programs in order to augment funds provided by the intelligence community and the DOD. These Navy funds would support changes to planned or developing programs to ensure that capabilities needed primarily by Navy users are included in NSS IRS systems. Supporting the development and testing of other novel sensors, such as the hyperspectral Naval EarthMap Observer (NEMO) satellite. Such hyperspectral systems have shown great potential to support both METOC and ISR needs.
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Navy’s Needs in Space for Providing Future Capabilities The creation of NSS ISR systems to provide capabilities needed by the Navy would clearly be valuable and perhaps even essential to the full implementation of Sea Power 21. Such systems can be envisioned, but many represent a technical challenge, given today’s state of technology. Recommendations Regarding Intelligence, Surveillance, and Reconnaissance Recommendation 4.1. The Department of the Navy should develop and fund directed operational analysis and science and technology (S&T) programs focused on addressing the Navy’s intelligence, surveillance, and reconnaissance shortfalls independent of whether or not the affected programs are managed by the Department of the Navy or the Department of Defense (DOD) Executive Agent for Space. The Department of the Navy should also work to transition the results of these efforts into planned and ongoing National Security Space programs. Recommendation 4.2. The Department of the Navy should continue its full support of National Reconnaissance Office intelligence, surveillance, and reconnaissance (ISR) activities and seek to extend its involvement in ISR program planning, development, and execution across other agencies’ ISR efforts. Recommendation 4.3. The Department of the Navy should provide budget authority to augment National Security Space intelligence, surveillance, and reconnaissance programs to permit program and system additions that address needs unique to Navy strategies (such as maritime operation). Recommendation 4.4. The Department of the Navy should coordinate with other agencies to support the development of advanced sensing technologies not currently part of the program plans of the DOD Executive Agent for Space. One such program that the committee believes has significant potential to provide new naval capabilities is the Naval EarthMap Observer (NEMO) hyperspectral imaging satellite. METEOROLOGY AND OCEANOGRAPHY The Navy has funded remote sensing research and development (R&D) in the areas of meteorology and oceanography nearly since the beginning of its involvement in space, but the military’s role in developing METOC satellites is changing. A 1994 Presidential Decision Directive mandated that the national military and civilian METOC communities consolidate all METOC satellites and
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Navy’s Needs in Space for Providing Future Capabilities sions was easily achievable. After tests with the first three experimental satellites proved successful, eight additional Block I satellites were launched to complete the design and testing phase of the GPS program. Although these satellites were intended to have a 3-year life span, they achieved an average operational life of almost 7 years.28 GPS relies on the principle of pseudo-ranging to provide accurate positioning to its users. Each satellite in orbit continuously transmits a radio signal with a unique code, called a pseudo-random noise (PRN) code, that includes data about the satellite’s position and the exact time that the coded transmission was initiated, as kept by the satellite’s onboard atomic clock. (GPS utilizes Coordinated Universal Time maintained by the U.S. Naval Observatory, in Washington, D.C.) A pseudo-range measurement is created by measuring the distance between a user’s receiver and a satellite by subtracting the time at which the signal was sent by the satellite from the time at which it is received by the user. Once three ranges (or distances) from three known positions are measured, a position in all three dimensions can be determined. In the case of GPS, however, a fourth satellite is generally needed in order to eliminate a common bias in the pseudo-ranges to all satellites caused by a lack of synchronization between the satellite and receiver clocks. Once this clock bias is eliminated by the presence of a fourth signal, a highly accurate three-dimensional position can be determined. Instead of transmitting one PRN code on one radio signal, each GPS satellite actually transmits two distinct spread spectrum signals that contain two different PRN codes, called the coarse acquisition (C/A) code and the precision (P) code. The C/A-code is broadcast on the L-band carrier signal known as L1, which is centered at 1572.42 MHz. The P-code is broadcast on the L1 carrier in phase quadrature with the C/A carrier and on a second carrier frequency, designated as L2, that is centered at 1227.60 MHz. The L1 C/A-code provides free positioning and timing information to civilian users all over the world; it is known as the standard positioning service (SPS). The timing information on the C/A-code is also used by some receivers to aid in the acquisition of the more accurate P-code. The P-code is normally encrypted using National Security Agency (NSA) cryptographic techniques, and decryption capability is available only to the military and to other authorized users. When encrypted, the P-code is normally referred to as the Y-code. Y-code availability through authorized decryption capability is known as the precise positioning service (PPS).29 28 National Research Council. 1995. The Global Positioning System: A Shared National Asset, National Academy Press, Washington, D.C. 29 National Research Council. 1995. The Global Positioning System: A Shared National Asset, National Academy Press, Washington, D.C.
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Navy’s Needs in Space for Providing Future Capabilities Before the PPS and SPS were officially established, GPS designers had anticipated that use of the Y- and C/A-codes would produce very different levels of positioning accuracy. Use of the Y-code was expected to result in 10 m accuracy, whereas the C/A-code was expected to provide accuracy of 100 m. Developmental testing of the Block I GPS satellites, however, showed that the accuracy difference between the two codes was not this significant. PPS accuracy was officially specified as 16 m spherical error probable (SEP), and SPS accuracy was set at 100 m SEP. This two-level accuracy arrangement was made possible on the Block II/IIA satellites through an accuracy denial method known as selective availability (SA). SA is a purposeful degradation in GPS navigation and timing accuracy that controls access to the system’s full capabilities. SA was accomplished in part by intentionally varying the precise time of the clocks onboard the satellites, which introduces errors into the GPS signal. An extensive study conducted by the National Research Council (NRC) in 1995 determined that the military effectiveness of SA was significantly undermined by differential GPS augmentations.30 For this and other, related civil-use reasons, the NRC recommended that SA be turned to zero, but the capability is retained for potential emergency use by the National Command Authority. By Executive Order in 2000,31 SA was turned to zero on the C/A-code L1 signal. SA and a new antispoofing encryption are still retained for the military Y-code. Differential GPS (DGPS) is the most widely used method of GPS augmentation; it can significantly improve the accuracy and availability of basic GPS. DGPS is based on knowledge of the highly accurate, geodetically surveyed location of a GPS reference station, which observes GPS signals in real time and compares their ranging information to the ranges expected to be observed at the DGPS fixed reference location. The differences between observed ranges and predicted ranges are used to compute corrections to GPS parameters, error sources, and/or resultant positions. These differential corrections are then transmitted to GPS users, who apply the corrections to their received GPS signals or computed position. As an example, the Wide-Area Augmentation System is a wide-area DGPS concept planned by the Federal Aviation Administration to improve the accuracy, integrity, and availability of GPS to levels that support flight operations in the National Airspace System, from en route navigation through Category I precision approaches. 30 National Research Council. 1995. The Global Positioning System: A Shared National Asset, National Academy Press, Washington, D.C. 31 Statement by the President Regarding the United States’ Decision to Stop Degrading Global Positioning System Accuracy, May 1, 2000. Available online at <http://www.ostp.gov/html/0053_2.html>. Accessed February 19, 2004.
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Navy’s Needs in Space for Providing Future Capabilities GPS user equipment varies widely in cost and complexity, depending on the receiver design and application. Receiver sets, which currently vary in price from less than $400 to over $30,000, can range from simple, one-channel devices that only track one satellite at a time and provide only basic positioning information, to complex, multichannel units that track all satellites in view and perform a variety of functions. Currently, GPS is the sole U.S. navigation satellite system for civil and military use. The Global Orbiting Navigation Satellite System The Russian Global Orbiting Navigation Satellite System (GLONASS) was developed in the early to mid-1980s by the military of the former Soviet Union. The GLONASS space segment also is designed to consist of 24 satellites, but these satellites are to be arranged in three orbital planes at 19,100 km (11,870 mi) altitude and at an inclination of 64.8 degrees rather than in six planes as for GPS. The full GLONASS constellation was scheduled to be operational in 1995.32 Currently, 11 GLONASS satellites are on-orbit. GLONASS differs from GPS in the way that the user segment differentiates one satellite from another. Instead of each satellite’s transmitting a unique PRN code as GPS satellites do, GLONASS satellites all transmit the same PRN code on different channels or frequencies. All of these frequencies, however, are in the L band near either of the two GPS downlink signals, which simplifies the task of designing integrated receivers. In addition, GPS and GLONASS use different time standards and coordinate systems. Discrepancies between these standards and coordinates exist and must be corrected by combined receivers if an integrated GPS/GLONASS capability is desired. Galileo In May 2003, the European Space Agency initiated a program to develop a global satellite navigation system (Galileo) with capabilities similar to those of GPS. However, the European Space Agency has asserted that Galileo will be built for civilian purposes, with sufficient positional and timing accuracy to support Europe’s integrated transport system. Galileo will consist of about 30 satellites (27 operational and 3 spares), positioned in three circular orbital planes at 23,616 km altitude and at an inclination of 56 degrees. Galileo will provide dual downlink frequencies in the L band, with a high degree of availability through an integrated failure-reporting system. The initial Galileo validation launches are planned for 2005 through 2006. Once the on-orbit validation phase has been 32 National Research Council. 1995. The Global Positioning System: A Shared National Asset, National Academy Press, Washington, D.C.
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Navy’s Needs in Space for Providing Future Capabilities completed, the remaining satellites will be launched to reach a full operational capability in 2008. Galileo will provide an additional search-and-rescue feature: each satellite will be equipped with a transponder that will be able to transfer distress signals from users’ transmitters to a Rescue Coordination Center for the activation of a rescue operation. At the same time, the system will provide a signal to the user, indicating that the situation has been detected and that help is being provided. It is intended that the Galileo user’s receiver equipment be interoperable with GPS and GLONASS. Current and Planned Capabilities The NAVSTAR GPS is recognized as the only satellite navigation system currently employed by the U.S. military and civil sectors. GPS is viewed as a key enabler to DOD transformation, as its precision positioning and timing capabilities enable continuous situational awareness, precision strike, autonomous operations, and precision synchronization of combat operations.33 Space Segment A space-based radio positioning system nominally consisting of a 24-satellite constellation, GPS provides navigation and timing information to military and civilian users worldwide. The constellation currently consists of Block II, IIA, and IIR satellites, arranged in six orbital planes of 55-degree inclination, at 10,988 nautical miles altitude. Each satellite completes one orbit in one-half of a sidereal day and therefore passes over the same location on Earth once every sidereal day (approximately every 23 hours and 56 minutes). The particular orbital configuration and number of satellites allows a user at any location on Earth to have at least four satellites in view 24 hours per day. Each Block II/IIA satellite is designed to operate for 7.5 years; the Block IIR satellites’ design life is 10 years. Block II/IIA provides SPS with a 16 to 24 m SEP on the C/A code L1 signal and PPS with a 16 m SEP on the P-code L1 and L2 signals.34 Block IIRs began replacing Block II/IIAs on July 22, 1997. There are currently eight Block IIR satellites on orbit, with the next launch planned for October 2003.35 Block IIR satellites boast dramatic improvements over the previous blocks. They also have reprogrammable satellite processors enabling in-flight 33 Global Positioning System Joint Program Office (GPS JPO). 2003. NAVSTAR GPS—Providing DOD Transformation, Washington, D.C., October 28. 34 Global Positioning System Joint Program Office (GPS JPO). 2003. NAVSTAR GPS—Providing DOD Transformation, Washington, D.C., October 28. 35 Global Positioning System Joint Program Office (GPS JPO). 2003. NAVSTAR GPS Overview, March.
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Navy’s Needs in Space for Providing Future Capabilities problem fixes. Eight Block IIR satellites are being modified to radiate the new, military-only (M-code) signal on both the L1 and L2 channels, as well as the more robust civil signal (L2C) on the L2 channel. The M-code signal is a more robust and capable signal architecture. It will have increased power and reduced vulnerability to signal jamming. In addition to the improved signals, the reliability of the GPS navigation message will be improved by adding more satellite monitoring stations. These additional stations will ensure that at least two stations will be able to simultaneously monitor each satellite. The data collected by these additional stations will then be combined with the data from the existing monitoring stations and sent to the master control station for processing. The result is improved accuracy of the navigation message broadcast by the satellite. The Block IIR positional accuracy today is 6.6 m. The first modified Block IIR (designated as the IIR-M) is planned for launch in 2004.36 Block IIF satellites are the next generation of GPS space vehicles. Block IIF provides all of the capabilities of the Block IIR-M with some additional benefits as well. Improvements include an extended design life to 12 years, faster processors with more memory, and a new civil signal on a third frequency (L5). Block IIF positional accuracy is planned to be 3.4 m. The first Block IIF satellite is scheduled for launch in 2006.37 Control Segment The GPS operational control segment (OCS) consists of the master control station, located at Schriever Air Force Base, Colorado; remote monitoring stations, located in Hawaii, Diego Garcia, Ascension Island, and Kwajalein; and uplink antennas located at three of the four remote monitoring stations and at the master control station. The four remote monitoring stations contribute to satellite control by tracking each GPS satellite in orbit, monitoring its navigation signal, and relaying this information to the master control station. The master control station is responsible for overall satellite command and control, which includes maintaining the exact orbits of each satellite and determining any timing errors that may be present in the highly accurate atomic clocks aboard each satellite. Major improvements are planned for the OCS. They include a new master control station with improved operator interfaces and Block IIR/IIF capabilities at Schriever Air Force Base, an alternate master control station at Vandenberg Air Force Base, and the establishment of additional monitoring sites at NGA locations around the globe.38 36 Global Positioning System Joint Program Office (GPS JPO). 2003. NAVSTAR GPS—Providing DOD Transformation, Washington, D.C., October 28. 37 Global Positioning System Joint Program Office (GPS JPO). 2003. NAVSTAR GPS Overview, Washington, D.C., March. 38 Global Positioning System Joint Program Office (GPS JPO). 2003. NAVSTAR GPS—Providing DOD Transformation, Washington, D.C., October 28.
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Navy’s Needs in Space for Providing Future Capabilities Modernized User Equipment Another effort under way at the GPS Joint Program Office (JPO) is that of developing a single modernized GPS receiver card to demonstrate M-code receiving and processing capability. The Services are expected to procure their own modernized user equipment based on the demonstrated performance of the M-code receiver card and to integrate this capability into their respective specific platform host receivers. The M-code card development effort is planned for completion by February 2008. To assist the GPS JPO with these activities, the DOD Executive Agent for Space recently requested that each of the Service departments conduct a GPS user equipment synchronization study to ensure that M-code user equipment development is synchronized with space- and ground-segment M-code capabilities. Global Positioning System Block III A future positioning system, the Block III Global Positioning System (GPS III), is in the planning stages. This system is intended to provide for the assured delivery of enhanced PNT signals and to offer related services to meet the needs of the next generation of GPS users. The GPS III program includes an integrated space-segment and control-segment system that incorporates the nuclear detonation detection system, a security infrastructure to provide user access to and protection of the entire system, and the incorporation of additional mission capabilities (including blue force tracking, search and rescue, and others). GPS III is envisioned to involve a total reexamination of the GPS architecture in order to achieve increased performance in hostile electromagnetic environments and possibly to feature the use of satellite-to-satellite links to improve control efficiencies. GPS III is also planned to incorporate a third civil signal and the use of spot beams to enable higher effective radiated power in small warfare theaters. It has been established that GPS III will have a minimum of +20 dB gain over Block IIA/IIR capabilities, with a long-term objective of +27 dB to achieve significant performance in jamming environments.39 GPS III positional accuracy is expected to be 1.9 m. The statement of objectives for GPS III was released in August 2001, as part of a system definition and risk reduction announcement by the GPS JPO.40 The first launch of a GPS III satellite is planned for 2012, with a full operational capability set for 2018. 39 Global Positioning System Joint Program Office (GPS JPO). 2003. NAVSTAR GPS—Providing DOD Transformation, Washington, D.C., October, 28. 40 Global Positioning System Joint Program Office (GPS GPO). 2001. Global Positioning System (GPS) III, System Definition and Risk Reduction (SD/RR), Statement of Objectives (SOO), Washington, D.C., August 30.
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Navy’s Needs in Space for Providing Future Capabilities Role of the Department of the Navy Assigned the primary lead in PNT for the Navy, the Oceanographer of the Navy is responsible for providing resource and program sponsorship. In addition, the Fleet Forces Command is responsible for forwarding the fleet’s GPS and PNT requirements, the Space and Naval Warfare Systems Command (SPAWAR) is assigned to develop and acquire naval GPS user equipment, ONR supports R&D on precision clocks, NRL monitors all GPS clock performance, and the U.S. Naval Observatory (USNO) maintains the master time reference for the DOD. Requirements The Navy, together with the other Services, participates in developing the functional and performance requirements for the GPS constellation, based on a number of military applications. Table 4.6 provides a summary of naval applications and associated positioning and radio frequency interference (RFI) resistance requirements. Table 4.7 provides a summary of military aviation and precision-guided munitions applications and associated positioning and RFI resistance requirements. Both of these tables were published in 1995 in the National Research Council report The Global Positioning System: A Shared National Asset,41 and although somewhat dated, they provide a good indication of requirements placed on GPS for positional accuracy, integrity, and RFI resistance. In addition, Appendix C of this report provides an evaluation of Sea Power 21 dependencies on current and projected PNT capabilities. The overall result of this comparison shows that precision PNT is critical for most Sea Power 21 military operations identified. User Equipment SPAWAR and the GPS and Navigation Systems Division of the SPAWAR Systems Center-San Diego, are the Navy’s principal acquisition and engineering development activities for GPS receiver development and integration. These organizations have provided technical, management, and engineering support for GPS receivers deployed on more than 120 Navy, Marine Corps, and Coast Guard platforms. SPAWAR Systems Center-San Diego also manages the GPS Central Engineering Activity Laboratory for evaluating GPS receivers. Timing Standards NRL, ONR, and USNO continue to maintain their leadership role in the research and development of precision time standards. As noted earlier, through 41 National Research Council. 1995. The Global Positioning System: A Shared National Asset, National Academy Press, Washington, D.C.
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Navy’s Needs in Space for Providing Future Capabilities TABLE 4.6 Naval Applications and Associated Positioning and Radio Frequency Interference (RFI) Resistance Requirements Application Accuracy RFI Resistance En route Pilotage and coastal waters 72.0 m CEP High Navigation Inland waters 25.0 m CEP High Open waters 2400.0 m CEP High Rendezvous 380.0 m CEP High Harbor 8.0 m CEP High Mine warfare Swept channel navigation and defensive mining 16.0 m CEP High Offensive mining 50.0 m CEP High Antimine countermeasures <5.0 m CEP High Geodetic reference guide 128.0 m CEP High Special warfare Airdrop 20.0 m CEP High Small craft 50.0 m CEP High Combat swimming 1.0 m CEP High Land warfare and insert/extraction 1.0 m CEP High Task group operations General task group operations 72.0 m CEP High Amphibious warfare Beach surveys 185.0 m CEP High Landing craft 50.0 m CEP High Artillery and reconnaissance <6.0 m CEP High Surveying Hydrographic <5.0 m (2 drms) High Ocean and geophysical deep ocean 90.0 m (2 drms) High Oceanographic 100.0 m (2 drms) High NOTE: CEP, or circular error probable, represents an accuracy that is achievable 50 percent of the time in two dimensions (latitude and longitude). Drms, or distance root mean square; 2 drms = 2.4 × CEP. SOURCE: National Research Council. 1995. The Global Positioning System: A Shared National Asset, National Academy Press, Washington, D.C. its Timation program NRL made significant contributions to the development of precision frequency standards suitable for spaceflight. NRL became a key participant in the development of advanced atomic clocks for flight in GPS satellites.42 Navy responsibility in precision time is currently designated by DOD Instruction 5000.2, Part 7, Section C, which calls for the Department of the Navy to carry out the following: Maintain the DOD reference standard through the USNO. Serve as the DOD precise time and time interval (frequency) manager, with responsibilities for 42 National Research Council. 2002. An Assessment of Precision Time and Time Interval Science and Technology, The National Academies Press, Washington, D.C.
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Navy’s Needs in Space for Providing Future Capabilities TABLE 4.7 Military Aviation and Precision-Guided Munitions Applications and Associated Positioning and Radio Frequency Interference (RFI) Resistance Requirements Application Accuracy RFI Resistance Aviation Low-level navigation and air drop 50.0 m (2 drms) High Non-precision sea approach/landings 12.0 m (2 drms) High Precision approach/landings (unprepared surface) 12.5 m (2 drms) High Precision sea approach/landings 0.6 m (2 drms) High Amphibious and antisubmarine warfare 50.0 m CEP High Anti-air warfare 18.1 m CEP High Conventional bombing 37.5 m CEP High Nuclear bombing 75.0 m CEP High Close air support/interdiction 9.0 m CEP High Electronic warfare 22.5 m CEP High Command, control and communications 37.5 m CEP High Air refueling 370.0 m CEP High Mine warfare 16.0 m CEP High Reconnaissance 18.1 m CEP High Magnetic and gravity survey 20.0 m CEP High Search and rescue/medical evacuation 125.0 m CEP High Mapping 50.0 m CEP High Precision-guided munitions 3.0 m CEP High NOTE: CEP, or circular error probable, represents an accuracy that is achievable 50 percent of the time in two dimensions (latitude and longitude). Drms, or distance root mean square; 2 drms = 2.4 × CEP. SOURCE: National Research Council. 1995. The Global Positioning System: A Shared National Asset, National Academy Press, Washington, D.C. Developing an annual DOD-wide summary of precise time requirements, and Coordinating the development of precise time and time interval techniques among DOD components.43 In addition to maintaining the DOD’s master clock, the USNO has an active research effort in clock development, timescale algorithms, and time transfer. NRL also maintains Navy expertise in space clock technology, providing services and advice to Navy and DOD programs related to the space-based clocks used in GPS and other systems.44 43 Department of Defense. 2002. DOD Instruction 5000.2, “Operation of the Defense Acquisition System,” Part 7, Section C, E. Andrews, Jr., J. Stenbit, and T. Christie, April 5. 44 National Research Council. 2002. An Assessment of Precision Time and Time Interval Science and Technology, The National Academies Press, Washington, D.C.
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Navy’s Needs in Space for Providing Future Capabilities Findings and Recommendations Regarding Position, Navigation, and Timing Precision position, navigation, and timing are critical to the Navy’s new operational concepts embodied in Sea Power 21. An important factor is the global nature of these concepts. Naval forces arrayed over thousands (even tens of thousands) of miles rely heavily on space-derived PNT to coordinate and execute these operations effectively. The U.S. Navy has filled an important role in the research and development of much of the technology that led to today’s highly capable satellite navigation systems and is currently engaged in the development of new technology for precision, space-qualified time standards. NAVSTAR GPS continues to be the premier spaceborne capability for military and civilian users of precision PNT. An ambitious program is under way to replenish and upgrade this system with advanced-technology spacecraft and a modernized ground control system to better serve the needs of military and civil users. The new GPS M-code signal will have a significant impact on the accuracy and reliability of the system. The GPS Joint Program Office has an important technology development effort under way to demonstrate a single GPS receiver card for M-code receiving and processing. All military Services are effectively involved in and working with the GPS JPO in the evolution of future-generation GPS III capabilities. Each Service also conducts receiver development programs that are keyed to GPS space- and ground-segment developments. Recommendation 4.19. The Department of the Navy should retain close ties with the Global Positioning System (GPS) Joint Program Office during the development of upgraded GPS space and ground segments. The Department of the Navy should also ensure that specific applications of integrated GPS (precision weapons systems, for example) are coupled to spacecraft capabilities that affect the resistance of these systems to radio-frequency interference (jamming). The Department of the Navy should conduct trade-off studies to determine the most cost-effective approach and strategy in developing guidance systems that rely on a combination of GPS and inertial guidance capabilities. Recommendation 4.20. The Department of the Navy should initiate a GPS synchronization study similar to that being conducted by the Air Force to ensure that M-code (military-only) user equipment development is synchronized with space-and ground-segment M-code capabilities. Recommendation 4.21. The Department of the Navy should sustain support to continue research and development in the area of precision timing standards and time transfer techniques, especially for potential use in future GPS space systems.
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Navy’s Needs in Space for Providing Future Capabilities SPACE CONTROL As increased reliance, if not outright dependence, on space capabilities becomes more widespread, space superiority and/or space control capabilities become more critical. While many of the details regarding space control have been and will remain classified, it is clear that naval forces will need the same level of security for space support as is needed by other joint forces. It is also clear that the Navy is well positioned to support the space control mission. The space control mission area includes the elements of space situational awareness, defensive counter-space, offensive counter-space, and related battle management and command and control. Space situational awareness provides predictive battlespace awareness. Defensive counter-space provides protection for friendly space capability. Offensive counter-space provides the ability to disrupt, degrade, deny, or destroy adversary space capability. Battle management and command and control provide the ability to integrate space control with other joint force activities in the prosecution of warfighting. Obviously, multiple electronic, directed-energy, or kinetic system applications and concepts can be envisioned for effectively engaging in space control. Platform basing can be an issue when such concepts are being considered, and from this perspective the potential advantages offered by sea-based platforms appear reasonably significant. Security classification restrictions prohibit meaningful discussions in this report of all space control efforts—specific plans, shortfalls, and technology gaps are largely classified. Suffice it to say that it would be in the best interests of the United States to pursue broad “disrupt, degrade, deny, or destroy” countermeasure capabilities to apply against any space-based capabilities that contribute to the threat posed by potential adversaries. Although the Under Secretary of the Air Force, as the DOD Executive Agent for Space, has the lead for space control efforts, it appears that other Services could support these activities within their own areas of competence. Thus, it would appear appropriate for the Navy to pursue potential sea-based space control concepts in close coordination with the Air Force. Recommendation 4.22. The Department of the Navy should explore potential sea-based space control concepts in coordination with the activities of the DOD Executive Agent for Space.
Representative terms from entire chapter: