SATELLITE MISSILE DEFENCE SYSTEM

Introduction.

1. United States of America has conducted extensive research and development on various types of missile defense technologies for decades. In December 2002, President Bush announced the United States would begin fielding several components of an anti-missile system designed to protect U.S. territory from attack by long-range (strategic) ballistic missiles under the project termed as National Missile Defence System. In July 2004, it fielded the first ground-based interceptor at Ft. Greely, Alaska, and since then has fielded and upgraded radars, built command and communication networks, and added interceptors at various Air Force Base inside USA and also pressing to field interceptors and a radar in Eastern Europe.

2. Hence, National missile defense (NMD) is a generic term for a type of missile defense intended to shield an entire country against incoming missiles, such as intercontinental ballistic missile (ICBMs) or other ballistic missiles. Interception might be by anti-ballistic missiles or directed-energy weapons such as lasers. Interception might occur near the launch point (boost phase), during flight through space (mid-course phase), or during atmospheric descent.

3. The system would use ground-based radars and space-based infrared and visible sensors, and the kill vehicle would be equipped with infrared and visible sensors intended to destroy targets by colliding with them in the mid-course of their trajectory, outside the earth’s atmosphere. The aim of this article is to familiarize with the exo-atmospheric sub sytem of this project or broadly study the application of various satellites in the missile defence system.

4. Aim: To Study the application of various types of satellites in the missile defence project with reference to United States of America’s ambitious NMD program.

Architecture of NMD.

5. The general architecture of the planned NMD system is now fairly well established, although decisions have not yet been made about all the details. The missile defense system can in general be placed into one of three categories, according to where in the trajectory of the incoming missile it is designed to intercept the target. A “boost-phase” defense system is designed to intercept during the boost phase of the attacking missile, in the first few minutes after it is launched and before the missile has released its warhead or warheads. A “terminal-phase” defense is designed to intercept a missile warhead in the final stage of its trajectory, as it reenters the atmosphere shortly before reaching its target. A “mid-course” defense system covers the territory in between: it is
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designed to intercept a warhead after it is released by the missile but before it reenters the atmosphere, when it is traveling through the vacuum of space. For an intercontinental- range missile, mid-course is the longest part of the trajectory.

6. Each of these three types of missile defenses has advantages and disadvantages. However, because the technical requirements are quite different for these three types of defense systems, any one type of defense is built to operate primarily in one regime and will not generally have capabilities in the other regimes. It is of course possible to include more than one of these three types of missile defense systems in a larger, multilayered system, but the planned US NMD system consists of only one layer.

7. The planned US NMD system is designed to intercept incoming warheads after their release by the missile, and before reentry into the atmosphere. Thus the system would be a mid-course defense, although it might have some capability to intercept incoming objects during the early part of the terminal phase of their trajectory, when they are still very high in the atmosphere. The interceptor would be land-based, exo-atmospheric (it is designed to home in on its target only above the atmosphere), and hit-to-kill (it would not use an explosive warhead to destroy an incoming warhead, but rather would need to directly hit its target to destroy it by impact).

8. The US NMD system is intended to defend only against long-range ballistic missiles. It is neither intended nor able to counter other types of missile threats to the United States, such as cruise missiles or short-range ballistic missiles launched from ships against coastal targets.

NMD System Evolution

9. NMD system has been planned to be build in several stages, with the capability of the system increasing with each stage. A “preliminary” architecture released by the Ballistic Missile Defense Organization (BMDO) in March 1999 describes the NMD system as being deployed in three phases.1 The first system configuration— dubbed the “capability-1” or “C-1” system— is designed to defend against an attack of a “few, simple” warheads. This initial system would subsequently be augmented to provide a “capability-2” or “C-2” system, designed to defend against a “few, complex” warheads. The stated goal of the NMD program is to deploy a “capability-3” or “C-3” system, designed to defend against “many, complex” warheads. The dividing line between the terms “simple” and “complex” is less well defined and more difficult to measure; these terms refer to the extent to which the attacker has incorporated countermeasures to fool or overwhelm the defense. The planned system is designed to be compatible with further expansions, including more ground-based interceptors deployed at

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additional sites and space-based weapons, such as the space-based laser under research and development by the United States.

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View from space of C-3 NMD System
The DSP/SBIRS-high system consists of 5-6 satellites, and approximately 24 SBIRS-low satellites are planned.

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Missile Defence System Operation

10. To intercept and destroy an incoming ballistic missile warhead, the US MD system must successfully perform a series of tasks. First, it must detect the launch of the ballistic missile and determine the general direction that the missile is going. Once the booster is done burning, the NMD system must detect the warhead(s) and any other objects accompanying them (such as missile debris or decoys), then begin to track these objects and predict their future trajectories. At some point in this process, the NMD system must discriminate the actual warhead(s) from the other objects and track the warhead(s) with sufficient accuracy to determine a predicted intercept point. If the system cannot discriminate the warhead(s) from other objects, it must instead track all the possible targets. The defense must then launch one or more interceptors towards the predicted intercept point for each target (or, if several potential targets are close together, for each cluster of targets). As the interceptor flies out, the defense must continue to track each target and send updated trajectory information to the interceptor. Once the interceptor is within a certain distance of its assigned target, it must release the kill vehicle. The kill vehicle must then detect the objects with its own sensors and, if necessary discriminate the warhead from the other objects. Finally, the kill vehicle must home on the warhead and maneuver to hit it directly.

11 Launch Detection. The System currently operates an early warning satellites in geosynchronous orbit that use infrared sensors to detect the hot plume of a missile booster in the early stage of its flight. These satellites, known as DSP (Defense Support Program) satellites, are able to detect the launch of any ballistic missile worldwide4 and provide the rough location of its launch point and rough information about its trajectory. Beginning in 2004, the DSP satellites will be replaced by a new system of early warning satellites known as SBIRS-high (Space-Based Infrared System—high Earth orbit), which will also use infrared sensors to detect missile plumes but will have improved capabilities. The data from the early warning satellites would be fed to the NMD battle management center. Based on the length of time the booster burns, the launch location, and the rough trajectory information provided by the early warning satellites, the battle management center would determine whether the missile poses a possible threat and whether the system might have to try to intercept it.

12 Warhead Detection and Tracking Once, the missile booster has stopped burning, it would no longer be visible to the early warning satellites. Using the information these satellites provide about the boost phase of the missile, other NMD sensors must then take over and detect and track the warhead(s) as well as any missile debris, decoys or other objects produced by the missile. By tracking an object over a period of time, the system would estimate its trajectory with increasing accuracy and determine the point in space to which the
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interceptor should deliver the kill vehicle, which would then home on the object and try to hit it. The sensors that the system would use to track the warhead(s) include the existing early warning radars; new X-band ground-based phased-array radars; and a satellite-based tracking system that would use infrared and visible light sensors. Because of the geographically large area and the Earth is curved, a ground-based radar at any one site could not detect and track all long-range missiles that could detonate in the United States. Moreover, if the interceptors are based at only one or two sites, but must cover the entire area of interest, they would need to fly far from their deployment site to intercept their targets. Thus, it would be important to track incoming objects as early as possible so that the interceptors can be launched as early as possible, particularly if the system is to observe the results of one or more intercept attempts before launching more interceptors.

13 Therefore, in addition to any radars deployed at interceptor sites, the NMD system requires a number of forward-deployed radars to track incoming targets and to guide the interceptor toward them. Using data from the early warning satellites that provides the approximate launch point and a rough trajectory of the incoming missile, the upgraded early warning radars would search the appropriate area of sky to detect the targets. The more accurate the information about the target trajectory that is provided to the radar, the smaller the area of sky the radar must search, and the further away it can detect the incoming targets. Thus, the NMD system will also deploy a number of new X-band radars6 that are specifically designed for NMD use and which have will have much better range resolution, and discrimination and tracking capabilities than the early warning radars.

14. The United States also plans to deploy a satellite based missile tracking system. Originally an SDI program called the Space Surveillance and Tracking System (SSTS), this program evolved into the Brilliant Eyes program, which was first renamed the Space and Missile Tracking System (SMTS) and then more recently the Space-Based Infrared System—low Earth orbit (SBIRS-low). SBIRS-low is the sensor that would provide the earliest tracking capability following a missile launch as well as worldwide coverage, but it is also the least developed and the furthest from deployment. It is an Air Force program intended for use by both national and theater missile defenses. The full system would have approximately 24 satellites equipped with both wide field of view infrared sensors designed to detect targets during boost phase (acquisition sensors) and narrow field of view infrared and visible light sensors designed to track targets during midcourse (tracking sensors). This satellite system is designed to provide track data accurate enough to guide interceptors, if necessary without assistance from other sensors. The track data from the ground-based radars and space-based sensors would be routed to the NMD battle management center. The center’s

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computers would then estimate the trajectory of each object being tracked and predict the future position of the object as a function of time.

15 Warhead Discrimination. If the missile deploys more than one object, then once the NMD system has detected the objects, it must determine which of these are warheads and which are not. Otherwise, the NMD system—with a limited number of interceptors—would risk simply running out of interceptors. While the warheads and decoys are traveling through the vacuum of space—where there is no air resistance—the lighter decoys and heavier warheads would all travel at the same speed. If the objects are roughly the same size, when they begin to reenter the atmosphere, the lighter decoys would slow down relative to the heavier warheads, allowing the warheads to be identified by the X-band radars because they can measure small changes in velocity. (The altitude at which a decoy will slow down relative to a warhead depends on the weight, size, and shape of the decoy.) Once the decoys slow down enough, the NMD system would be able to determine which objects are the warheads.

16. However, the kill vehicle has a minimum intercept altitude, below which it cannot intercept a target. Because the kill vehicle uses an infrared sensor to detect and home on the target, it would be blinded by the heating that would occur as the sensor flies through the atmosphere. Moreover, the kill vehicle will have an airframe that is not aerodynamic and would thus become unstable in the atmosphere where it would experience lift and drag forces. If this minimum intercept altitude is comparable to the altitude at which the radars can first discriminate the lightweight decoys from a heavier warhead, the NMD interceptor may not be able to fly low enough to even make an intercept attempt. The NMD system would thus need to discriminate the warheads from the decoys before these objects reenter the atmosphere.

17. The ground-based X-band radars can make very detailed measurements of the motions of an incoming object (such as whether it is wobbling or rotating) as well as some of its physical characteristics, including its length (projected along the direction between the target and radar), certain structural details, its velocity, and its radar cross section. The radar cross section of an object is a measure of the apparent size of the object as seen by the radar and depends on the physical size of the object, on how well its surface reflects or absorbs radar waves, and on the shape of the object. In some circumstances, the X-band radars may be able to produce a two- or even three-dimensional image of a target

18. . SBIRS-low is specifically designed to help with target discrimination by adding different types of sensors to the NMD system. When SBIRS-low becomes available, the NMD system could also attempt to discriminate decoys from warheads by using infrared sensors, which detect the heat radiated by an object.
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Thus, if it were known that a warhead was hotter (or cooler) than the decoys, the infrared sensor should be able to distinguish one from the other. In addition, SBIRS-low will have a sensor in the visible spectrum that detects reflected sunlight and may provide other types of information about incoming objects in a daytime attack. The NMD battle management center would integrate the information from these various sensors and decide which objects the system should try to intercept.

19. Finally, if the decoys and warheads were spaced closely enough together, the infrared and visible sensors on the kill vehicle itself could be used to attempt to discriminate the warheads from the decoys. This strategy could be implemented only if the objects were spaced closely enough that the kill vehicle would have time to maneuver and reach any of these objects once it determined which one was the warhead. When the kill vehicle first acquired the target, which could occur at ranges as great as one thousand kilometers or more, its infrared sensors would provide data similar to that from SBIRS-low. This would permit the NMD system to determine the temperature of an object and the intensity of the infrared radiation emitted by it. However, as the kill vehicle drew closer to the target, its spatial resolution would improve and it would increasingly be able to image the target and other objects close to it. These images could also potentially be used to discriminate the warhead from the other objects. In addition, the first kill vehicle could send such images of closely spaced objects to the NMD system to help subsequent kill vehicles discriminate the warhead from decoys and other objects. This strategy would rely on firing multiple interceptors against each potential warhead.

20. Interceptor Guidance Once the NMD system has decided which object to intercept, it would launch one or more interceptors towards the predicted intercept points. The NMD interceptor would consist of a three stage missile booster and an exo-atmospheric kill vehicle (EKV), which would separate from the booster once it has burnt out. The booster would accelerate the kill vehicle to a speed of 7–8 kilometers per second. Once the kill vehicle was above the atmosphere, it could maneuver by using small thrusters to divert it in a chosen lateral direction. In order to increase the probability of a successful intercept, the NMD system would likely fire multiple interceptors per target.

21 If time permits, the NMD system would likely use a “shoot-look-shoot” tactic whereby it would fire additional interceptors at a target only if the previous ones failed to hit it. However, this tactic may be possible only if the incoming warhead’s trajectory takes it close enough to the interceptor launch point. Otherwise the fly-out time for the second interceptor could be too long to permit a second launch to be delayed until it was certain that the first interceptor had failed. In this case, the NMD system would have to use the less efficient strategy of firing several interceptors at once or in quick succession (known as a salvo
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launch).Once an interceptor has been launched at a specific target, the NMD system would continue to track the target and the interceptor in order to update the predicted intercept point. The job of the NMD system would then be to guide the booster and the kill vehicle to the point in space where the kill vehicle should be able to detect the target using its own sensors (known as the acquisition point). From that point the kill vehicle should be able to home on and hit the target. The acquisition point would be calculated by the NMD system based on the estimated trajectory of the target. The NMD system would use an In-Flight Interceptor Communications Systems (IFICS) to relay communications from the battle management center to interceptors that have flown over the horizon. The IFICS would consist of several ground stations deployed at forward locations.

22. Kill Vehicle Homing. The kill vehicles are designed to destroy their targets by colliding with them at high speeds. Once the kill vehicle is close enough to its target, its on-board infrared and visible sensors would be used to detect the target and home on it. In order for this to be possible, the target must be in the searchable field of view of the sensors when the kill vehicle reaches the acquisition point. The region of space that is within the kill vehicle’s field of view and within which the kill vehicle can maneuver to make an intercept is referred to as the interceptor “basket.” During the homing process, the kill vehicle would continue to receive information on the target, based on data from the radars and SBIRS-low satellites, which could assist in discrimination. The kill vehicle would use small thrusters to maneuver. As noted above, the kill vehicle has a minimum intercept altitude, below which it cannot intercept a target. The Ballistic Missile Defense Organization is trying to achieve a minimum intercept altitude of 130 kilometers

23. Battle Management. As mentioned above, once a ballistic missile is launched, data from the early warning satellites would be fed to the NMD battle management center where computers would determine whether the missile might need to be engaged by the NMD system. Of course, more than one missile might be launched at a time or in quick succession. The track data from the ground-based radars and space-based sensors would also be routed to the NMD battle management center. The center’s computers would then estimate the trajectory of each object being tracked and predict the future position of the object as a function of time. In order to develop trajectory information for multiple objects that are similar in appearance and are close to each other, the system would need to consider all the possible trajectories that could be consistent with successive position measurements. In addition, the battle management center would need to integrate all the sensor data to determine which objects are potential warheads. Finally, the center would need to make kill assessments, to determine which warheads the NMD system had failed to intercept. This would be essential to implement a “shoot-look-shoot” strategy.

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Space Based Infrared System (SBIRS) SATELLITE

24. An upcoming launch of the United States Air Force Space Based Infrared System (SBIRS) satellite destined for geostationary earth orbit (GEO) will be another step in the transition from the Defense Support Program (DSP), a ballistic missile warning system born of the cold war, to the modernized and multi-mission SBIRS system. SBIRS GEO-1 satellite is scheduled for launch on 6 May 2011 from Cape Canaveral Air Force Station (CCAFS) carrying a payload with a pair of infrared sensors, both of which bring improved detection sensitivity, increased sensor temporal frame rate, and extremely high pointing agility. Although it is a long time in coming, the SBIRS GEO satellite is expected to continue the evolution of the system, and also to generate a host of new military and civil applications of the infrared data.

25. This new GEO satellite will add to the modernization that began with the achievement of Initial Operations Capability of the SBIRS Mission Control Station (MCS) in 2001. Mission processing and control of DSP satellites was consolidated into a single Continental United States ground site, the MCS, and significantly improved the accuracy of the missile warning products produced by the system. Modernization continued with successful deployment of new infrared payloads that are deployed on host satellites in a highly-elliptical earth orbit (HEO), with operational acceptance achieved in 2008. The SBIRS HEO infrared payloads are highly sensitive instruments that are providing data collection for SBIRS missile warning and technical intelligence missions, and are also spawning new data exploitation initiatives. Data collected by the SBIRS HEO sensors are rich with new content heretofore not available, and scientists and engineers are seeking new data processing algorithms to dig deeper into the imagery. Indeed, unexpected observations have been discovered, already resulting in support to other government agencies (e.g., analysis of test failure) and new mission areas.

26. SBIRS GEO-1 carries a scanning sensor similar to, but more agile than, the already-deployed SBIRS HEO sensor, and a staring sensor. The scanning sensor will generally provide global surveillance, with the staring sensor intended to interrogate areas of interest around the globe with even more enhanced sensitivity and revisit time. Support to the theater missile warning mission, missile defense mission, technical intelligence mission, and the evolving battlespace awareness mission area, were the drivers for design of the GEO staring sensor. As a result, it will provide very fast re-pointing ability, high sensitivity, and small revisit time for areas of interest, as well as for tracking dim ballistic missiles to booster burnout. The staring sensor will also provide a mode of operation that allows it to continuously stare at a site with very high refresh rate, as well as flexibility in spectral band selection. Enhanced sensitivity and revisit time from the SBIRS sensors bring opportunity for earlier detection of missile launches, higher 11

confidence detection of new dimmer and shorter-duration events, and more accurate estimation of missile trajectory parameters.
27. Although the SBIRS program plans are to bring the GEO scanning sensor into full mission operations within about 16 months of launch, the staring sensor will no doubt be used even before then, to collect data and perform mission processing off line. The off-line processing is expected to provide engineers opportunity to learn how to best process the data, understand the full capability of the sensor, and begin mining the observations for exploitation opportunities. Just as new missions evolved over the past 40 years by exploiting the DSP sensor data (e.g., for early warning of forest fires, volcano eruptions, to mention only a few) the same will surely occur with the new SBIRS sensors.

28. Within the SBIRS program, the thought is never far away of those who came before us, who developed the remarkable DSP satellite system, which was hugely successful and provided, and continues to contribute to, very reliable performance. We recognize the keen vision, superb engineering expertise, and passionate dedication of those who have gone before us. It is the foundation for SBIRS, and the act we strive to follow. As we continue the work of transitioning to the new system, we expect the new capabilities to even more strongly impact support to our war-fighters, and security for our country and allies. We also expect new visions to be created that will expand the overhead persistent infrared missions as we continue to move through the 21st century.

CONCLUSION

29. It is a truism that the development or deployment of a weapons system often leads to the development and deployment of another system to counter the first. Indeed, the planned satellite missile defense is itself such a response to ballistic missiles. Thus, one must expect that countries that want to acquire or maintain the ability to attack with intercontinental-range ballistic missiles will respond to the deployment satellite missile defense system by incorporating countermeasure strategies and technologies to defeat it.

30 However, there are many operational and technical reasons why it is much more difficult to build an effective missile defense system than to build an effective offense. These inherent advantages can enable an attacker to compensate for other nations’ technical superiority.

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View from space of C-1 NMD System
The DSP/SBIRS-high system consists of 5-6 satellites.
CONTENTS
|Ser No |Title |
|1. |INTRODUCTION |
|2. |ARCHITECTURE OF NMD |
|3. |NMD SYSTEM EVOLUTION |
|4. |MISSILE DEFENSE SYSTEM OPERATION |
|5. |SPACE BASED INFRARED SYSTEM SATELLITE |
|6. |CONCLUSION |

1. INTRODUCTION 2. ARCHITECTURE OF NMD 3. NMD SYSTEM EVOLUTION 4. MISSILE DEFENSE SYSTEM OPERATION 5. SPACE BASED INFRARED SYSTEM SATELLITE 6. CONCLUSION

SATCOM SUBMISSION ON
SATELLITE MISSILE DEFENCE SYSTEM