Despite some missile defence advocates' claims that 24 satellites could shape the footing of a boost-phase space-based missile interceptor (SBI) system, many physicists make non agree.1 H5N1 ameliorate inquiry is how could a satellite constellation of this size best contribute to U.S. missile defense? A 24-satellite constellation is also pocket-size for boost-phase missile defense. Hundreds or thousands of satellites would endure needed to furnish continuous coverage of fifty-fifty a pocket-size threat part similar North Korea. A similar constellation could run for limited midcourse-phase missile defense, but non all threat regions could endure covered past times the same architecture as well as midcourse intercepts are difficult, requiring detailed tracking as well as target discrimination information to avoid beingness fooled past times decoys. A constellation of this size would work, however, for space-based sensor (SBS) systems, which could discovery missiles during their midcourse stage equally long equally they tin hold line-of-sight contact.
Introduction
For almost twoscore years, missile defence advocates inward the USA get got envisioned a constellation of satellites positioned inward overlapping orbits about the world as well as loaded amongst weapons designed to intercept missiles before they make their targets. One of the space-based missile interceptor (SBI) systems most unremarkably proposed is a "hit-to-kill" model, where interceptors destroy missiles or warheads during flying using the kinetic liberate energy of impact.2 In a hit-to-kill SBI system, these orbiting interceptors give the axe thrusters as well as alter their trajectory inward lodge to hitting their targets. The make of a space-based interceptor—the distance it tin move away from its initial position on orbit—is limited past times how fast the interceptor tin maneuver out of orbit, the amount of propellant onboard, as well as the allotted fourth dimension before it must make its target. When an SBI arrangement is modeled, these constraints run together to greatly bound the efficiency of whatsoever interceptor constellation as well as increment the required number interceptors on orbit to offering coverage to threat regions on the Earth's surface.
Advocates for deploying a constellation of SBIs ofttimes mention the findings from a classified 2011 Institute for Defense Analyses (IDA) written report to back upward their claim that SBIs could offering effective boost-phase missile defence at a reasonable cost.3 But before this year, the Union of Concerned Scientists identified a mutual fault inward interpreting IDA's results: a constellation of 24 satellites could only endure useful for midcourse missile defense—intercepting missiles afterwards their engines goal burning as well as before they re-enter the atmosphere.4 Boost-phase missile defense—targeting missiles inward their start as well as most vulnerable stage of flight—would require hundreds or thousands of interceptors.5
According to an unclassified alphabetic lineament describing details from the 2011 IDA report, 24 satellites could shape a "limited" SBI layer as well as toll some $26 billion over its 20-year operational lifetime, including a total replacement afterwards 10 years. The IDA analysis goes on to annotation that a "global" satellite constellation of 960 satellites, which could probable offering boost-phase coverage, would toll some $282 billion over the same period.6
How effective would a 24-satellite SBI layer endure defending against missile launches inward their boost phase? What almost inward the midcourse phase? What if 24 satellites were used for a dissimilar missile defence role entirely, similar space-based sensing for midcourse tracking as well as discrimination?
A 24-Satellite Constellation is Not Enough for a Boost-Phase SBI Layer
According to analysis from the American Physical Society, RAND Project Air Force, as well as the CSIS Aerospace Security Project, a 24-satellite constellation is non plenty for boost-phase missile defense.7 When placed inward a constellation to offering optimal coverage of North Korea, for example, 24 satellites would instruct out the Korean peninsula completely uncovered over 75 per centum of the time.8 Furthermore, these satellites would go past times overhead inward visible, predictable paths. An adversary would know amongst certainty when the constellation would furnish no coverage as well as programme its laid on accordingly. Since whatsoever gap inward coverage is effectively no coverage, whatsoever constellation that does non offering continuous coverage does non meaningfully contribute to the broader United States' Ballistic Missile Defense System (BMDS).
Without a doubt, a 24-satellite SBI arrangement is physically incapable of maintaining continuous coverage over fifty-fifty a pocket-size relatively part similar Korea for boost-phase missile defense.
Figure 1: Boost-Phase Coverage for a 24-Satellite SBI System. nine If 24 satellites were oriented inward 4 orbital planes, at an height of 300 kilometers as well as 40.5° inclination, Democratic People's South Korea (ranging from some 38°N to 43°N) would endure left uncovered over 75 per centum of the time.10
Although the 2011 IDA written report notes that each satellite could endure capable of carrying 4 interceptors each, a constellation of 24 satellites amongst 4 interceptors apiece does non furnish ameliorate boost-phase coverage than a constellation of 24 satellites amongst 1 interceptor apiece. If 1 interceptor cannot make its target missile inward time, neither tin the other three.11
Without a doubt, a 24-satellite SBI arrangement is physically incapable of maintaining continuous coverage over fifty-fifty a pocket-size relatively part similar Korea for boost-phase missile defense.
24 Satellites Could Be Enough for a Midcourse SBI Layer
Depending on its orientation, a 24-satellite SBI layer could effectively contribute to limited midcourse missile defense. Since the midcourse stage represents the bulk of a missile's flying (upwards of 10 minutes for an intercontinental ballistic missile), interceptors would get got much to a greater extent than fourth dimension to make their target than they would during a missile's boost stage (which may only terminal 2 or 3 minutes).12A 24-satellite constellation inward the same orbits equally described inward the previous department would furnish continuous midcourse missile defence coverage for missile trajectories below 60°N, which would encompass a North Korean missile strike targeting Guam as well as the West Coast of the continental United States, including Seattle as well as Los Angeles.13 Missiles traveling to the USA from Russia, China, or Iran, however, would move over the Earth's northward pole as well as would non endure fully covered past times this exceptional SBI constellation.
Figure 2: Midcourse-Phase Coverage for a 24-Satellite SBI System. xiv If 24 satellites were placed inward the same orientation equally those inward Figure 1, the missiles that make their midcourse stage betwixt 60°S as well as 60°N latitude would ever endure inside make of at to the lowest degree 1 interceptor. For some latitude bands, similar that betwixt 20°N as well as 40°N, at that spot are ever 2 or to a greater extent than interceptors inside reach.
Although 24 satellites may endure plenty to make a North Korean missile during its midcourse phase, an interceptor would non endure able to successfully strike its target without sufficient midcourse target discrimination—specifically a greater fidelity of tracking information to distinguish the warhead from decoys as well as debris. To attain this capability, some missile defence advocates suggest the deployment of a space-based sensor (SBS) layer.15
24 Satellites Are Enough for an SBS Layer
Although a constellation amongst only 24 satellites offers limited continuous midcourse-phase as well as no continuous boost-phase coverage, the same number of satellites could furnish splendid world-wide sensor coverage.
The already-deployed Space-Based Infrared System (SBIRS) satellites rail missiles inward their boost phase—honing inward on the oestrus signatures produced past times rocket engines using infrared sensors. They are non designed to rail missiles during their midcourse stage when they must endure observed equally relatively mutual frigidity objects against the fifty-fifty colder background of space. After a missile's engines burn downwardly out, the oestrus signature goes dark, as well as they cannot endure easily tracked using infrared systems. An SBS layer inward depression world orbit could usage radar or optical sensors to monitor missiles mid-flight—well past times the boost phase—discriminating betwixt warheads, decoys, or other debris created during the midcourse phase.16
The proposal to create an SBS layer for midcourse tracking as well as discrimination is non new.17First proposed equally role of the Reagan administration's Strategic Defense Initiative, an SBS layer—nicknamed "Brilliant Eyes"—was start envisioned inward the belatedly 1980s.18 In the 1990s, the Clinton direction included an SBS layer inward its proposal for the SBIRS program, calling it "SBIRS-low." xix In 2001, the Missile Defense Agency took command of the program, renaming SBIRS-Low the "Space Tracking as well as Surveillance System" (STSS), as well as scaled the programme dorsum to simply 2 demonstrator satellites (STSS 1 as well as STSS 2), which were launched inward 2006.20
Although STSS was originally proposed equally a 20- to 30-satellite constellation, at that spot are currently no plans to grapple the program, as well as the 2 demonstrator satellites are non integrated into the overall BMDS architecture. 21
Suppose a 24-satellite SBS arrangement were launched to the same height as well as inclination of the 2 STSS demonstrator satellites. That constellation would offering full-Earth coverage, sensing missiles launched from anywhere on world during their midcourse phase.
Figure 3: Sensor Coverage for a 24-Satellite Space-Based Sensor Layer. 22 If 24 satellites were oriented inward constellation amongst parameters similar to the 2 STSS demonstrator satellites (1350 km circular orbits amongst 58° inclination),23 missiles launched from anywhere on world would endure inside persuasion of at to the lowest degree 2 sensors for the entirety of the midcourse stage of their flights. Missiles flying to significantly higher latitudes than 200 km could endure sensed past times many to a greater extent than than 2 satellites.
Space-based sensors remain inward orbit equally they rail missiles as well as discriminate betwixt a missile's warhead as well as other debris that may get got been created during flight. Unlike interceptors, a sensor's make is constrained past times the Earth's horizon (a sensor cannot rail a missile if it is on the other side of the world) as well as the atmosphere (observing a missile at a depression angle relative to the horizon tin crusade indicate fade as well as distortion). 24 Thus, missiles that make higher altitudes tin endure seen past times to a greater extent than sensors inward the 24-satellite constellation. If a missile reaches an height of 1000 kilometers or higher, for example, 5 or to a greater extent than sensors inward this hypothetical constellation tin rail it for a part of its trajectory, no affair its destination or origin. This redundancy is extremely helpful since the accuracy of missile tracking as well as discrimination only increases amongst additional sensors inward contact.
[A]n interceptor would non endure able to successfully strike its target [in its midcourse phase] without sufficient midcourse target discrimination.
Conclusion
SBI systems are regularly touted for their mightiness to strike missiles during their boost phase. H5N1 constellation amongst only 24 satellites, however, is non plenty to endure effective at boost-phase missile defense. When considering midcourse intercepts, the same constellation fairs better—offering limited coverage to some portions of the Earth.
An SBS layer, on the other hand, would operate good amongst only 24 satellites inward depression world orbit. An added make goodness is that the same constellation, when non beingness used to rail missiles, could endure used to rail other satellites inward space. It would complement the Air Force’s existing infinite situational awareness architecture, to ameliorate rail other infinite objects as well as to a greater extent than accurately warn of potential collisions.24
Due to the coverage limitations of hit-to-kill SBIs, a constellation of 24 satellites would endure a to a greater extent than effective missile defence arrangement if it supported sensors rather than interceptors.
Thomas G. Roberts is a programme coordinator as well as enquiry assistant for the Aerospace Security Project at the Center for Strategic as well as International Studies inward Washington, D.C.
CSIS Briefs are produced past times the Center for Strategic as well as International Studies (CSIS), a private, tax-exempt establishment focusing on international world policy issues. Its enquiry is nonpartisan as well as nonproprietary. CSIS does non get got specific policy positions. Accordingly, all views, positions, as well as conclusions expressed inward this publication should endure understood to endure solely those of the author(s).
© 2018 past times the Center for Strategic as well as International Studies. All rights reserved.
1 David Wright, "24 Space-Based Missile Defense Satellites Cannot Defend Against ICBMs," All Things Nuclear(blog), August 10, 2018, https://allthingsnuclear.org/dwright/24-space-based-interceptors.
2 Donald R. Baucom, “The Rise as well as Fall of Brilliant Pebbles,” Journal of Social, Political, as well as Economic Studies 29, no. 2 (Summer 2004): 143.
3 "Letter Regarding the 2018 Missile Defense Review (MDR)," Ted Cruz to James Mattis, Feb 22, 2018, https://innaiyaveli.blogspot.com//search?q=; "Space-Based Missile Defense," CSIS Aerospace Security.
8 Calculated for a Walker constellation of 24 satellites inward 4 planes at 40.5° inclination, orbiting at 300 km higher upward the Earth's surface, amongst a maximum de-orbiting velocity of six km/s as well as a 120 2nd reply time.
9 Learn to a greater extent than almost this model's methodologies at aerospace.csis.org/sbi.
10 For each figure inward this report, interceptor or sensor coverage is mirrored over the southern hemisphere, amongst latitudes of the same magnitude receiving equal coverage.
11 "Letter Regarding the 2011 Institute for Defense Analyses (IDA) Report on Space-Based Missile Defense," Patrick J. O'Reilly to Jon Kyl, June 22, 2011, http://aerospace.csis.org/wp-content/uploads/2018/09/OReilly2011.pdf, 2.
12 David K. Barton et al., "Report of the American Physical Society Study Group on Boost-Phase Intercept Systems for National Missile Defense," 23.
13 Calculated for the same Walker constellation of 24 satellites equally the previous department amongst a 720 2nd reply time.
14Learn to a greater extent than almost this model's methodologies at aerospace.csis.org/sbi.
15 Brian Everstine, "MDA, DOD Leaders Call for Space Sensors to Deal With Hypersonic Threats," Air Force Magazine, September 4, 2018, http://www.airforcemag.com/Features/Pages/2018/September 2018/MDA-DOD-Leaders-Call-for-Space-Sensors-to-Deal-With-Hypersonic-Threats.aspx.
16 Phillip Swarts, "Missile Defense Tracking Systems Need to Move to Orbit, Leaders Say," SpaceNews.com, Dec 15, 2016, https://spacenews.com/missile-defense-tracking-systems-need-to-move-to-orbit-leaders-say/.
17 Marcia S. Smith, Military Space Programs: Issues Concerning DOD's SBIRS as well as STSS Programs (Washington, D.C.: Congressional Research Service, Library of Congress, 2006), 1, https://fas.org/sgp/crs/weapons/RS21148.pdf.
18 Office of Technology Assessment, SDI: Technology, Survivability, as well as Software, OTA- ISC-353 (Washington, DC: U.S. Government Printing Office, 1988), 9, http://govinfo.library.unt.edu/ota/Ota_3/DATA/1988/8837.PDF.
19 Thomas Karako, Ian Williams, as well as Wes Rumbaugh, "Missile Defense 2020: Next Steps for Defending the Homeland," Center for Strategic as well as International Studies, Apr 6, 2017, https://www.csis.org/analysis/missile-defense-2020, 39.
20 Ibid., 97.
21 Ibid., 96.
22 Learn to a greater extent than almost this model's methodologies at aerospace.csis.org/sbi.
23 “Space Tracking as well as Surveillance System,” Missile Defense Agency, July 28, 2016, http://www.mda.mil/global/documents/pdf/stss.pdf.
24 Masking limitations due to the Earth's atmosphere are non taken into trouble organization human relationship inward the model presented inward Figure 3.
25 Thomas Karako et al., "Missile Defense 2020," 101.
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