Patty-Jane Geller

Missile defense is a critical component of the U.S. national security architecture that enables U.S. military efforts and can protect critical infrastructure, from population and industrial centers to politically and historically important sites. It can strengthen U.S. diplomatic and deterrence efforts and provide both time and options to senior decision-makers during crises involving missiles that fly on ballistic and non-ballistic trajectories.

The Growing Missile Threat

Missiles remain a weapon of choice for adversaries who view them as cost-effective and symbols of power compared to other types of conventional weapons.1 The number of states that possess missiles will continue to increase, as will the sophistication of these weapons, as modern technologies become cheaper and more widely available.

In 2022, North Korea intensified its missile testing efforts, conducting its first test of an intercontinental ballistic missile (ICBM) since 2017 in addition to tests of several shorter-range missiles and even a hypersonic missile capable of maneuvering during flight.2 These tests allow Pyongyang to keep improving and adapting its missile program and by so doing add to an already formidable threat. North Korea also continues to advance its ability to overcome missile defenses, including those that protect the United States, with missiles that supposedly can carry multiple warheads and decoys.3

Iran continues to modernize and proliferate its regional missile systems. Its recent launches of solid-fuel rockets demonstrate that Iran has the ability to build and successfully launch sophisticated missiles, which implies in turn that it has or is developing the ability to advance to an ICBM capability.4

China and Russia, in addition to their vast ballistic missile inventories, are investing in new ground-launched, air-launched, and sea-launched cruise missiles that uniquely challenge the United States in different domains and are deploying new hypersonic glide vehicles.5 China is rapidly building hundreds of new missiles, including modern ICBMs that can carry multiple warheads and theater-range missiles that can strike U.S. assets with precision.6 Russia is developing entirely new capabilities, such as a nuclear-powered cruise missile, that are intended to avoid U.S. sensors and missile defenses. It has employed its Kinzhal hypersonic missile for the first time in Ukraine.7 Russia’s conventionally armed sea-launched and air-launched cruise missiles can strike strategic nodes within the U.S. homeland, even from Russian territory, and China is developing a long-range conventional strike capability of its own.8

The Strategic Role of Missile Defense

Missile defense plays a critical role both in deterring an attack and in mitigating the damage to U.S. forces, infrastructure, and population centers in the event deterrence fails. The ability to deter an attack depends on convincing the adversary that the attack will fail, that the cost of carrying out a successful attack is prohibitively high, or that the consequences will outweigh the perceived benefit of an attack. A U.S. missile defense system strengthens deterrence by offering a degree of protection to U.S. populations, military forces, and allies, making it harder for an adversary to threaten them with missiles. By raising the threshold for missile attack, missile defense can complicate an adversary’s planning, remove the option for a “cheap shot” against the United States and its allies, and perhaps make the adversary think twice before launching an attack. By protecting key U.S. assets, missile defense also mitigates an adversary’s ability to intimidate or coerce the United States into making concessions.

Missile defense systems help to enable U.S. and allied conventional operations. During a regional conflict, adversaries could deny the United States the ability to conduct offensive operations by targeting U.S. and allied forward-deployed personnel or military assets. In addition, they might try to decouple the United States from defense of its allies by threatening to strike U.S. forces or the U.S. homeland if the United States intervenes in a regional conflict. Missile defenses can therefore strengthen the credibility of U.S. extended deterrence by making it easier for the U.S. military to introduce reinforcements that can move more freely through a region.

A missile defense system gives decision-makers more time to choose the most de-escalatory course of action. Without the ability to defend against an attack, U.S. authorities would be limited to an unappealing set of responses that could range from preemptive attacks to acceding to an enemy’s demands or actions. By assuring some level of protection, robust missile defense systems would affect the dynamics of decision-making by removing the need to take immediate action. Missile defense can therefore be profoundly stabilizing.

Finally, missile defense minimizes damage if deterrence fails. A strong missile defense system would not only help to protect countless American lives; it would also help to keep U.S. forces available during a fight. During a campaign against China in the Indo-Pacific, for example, missile defenses deployed in the region could lower the loss rate for U.S. forces compared to the rate of replacement, thereby extending the war effort and giving U.S. forces more time to prevail.

The U.S. Missile Defense System

The U.S. missile defense system has three critical physical components:

• Sensors,
• Interceptors, and
• Command and control infrastructure that provides data from sensors to interceptors.

Of these, interceptors receive much of the public’s attention because of their visible and kinetic nature. Components of missile defense systems can be classified based on the phase of flight during which intercept occurs, although some—for example, the command and control infrastructure or radars—can support intercepts in various phases of flight. Interceptors can shoot down an adversary ballistic missile in the boost, ascent, midcourse, or terminal phase of its flight. As cruise missiles and hypersonic glide vehicles continue to proliferate, the Missile Defense Agency (MDA) and the military services must therefore consider intercept in the boost, glide, or terminal phase of flight.

Another way to classify missile defense systems is by the range of an incoming missile (short-range, medium-range, intermediate-range, or intercontinental-range) that an interceptor is designed to shoot down. An interceptor’s flight time determines both the time available to conduct an intercept and the optimal interceptor placement to improve intercept probability. With ICBMs, the United States has “30 minutes or less”9 to detect the missile, track it, provide the information to the missile defense system, find the optimal firing solution, launch an interceptor, and shoot down the incoming missile, ideally with enough time to fire another interceptor if the first attempt fails. The time frame is shorter for intercepting short-range, medium-range, and intermediate-range ballistic missiles.

Finally, missile defense can be framed by the origin of interceptor launch. At present, U.S. interceptors are launched from the ground or from the sea. In the past, the United States explored possible ways to launch interceptors from the air or from space, but such efforts have been limited since the U.S. withdrawal from the Anti-Ballistic Missile Treaty in 2002.10

The current U.S. missile defense system is a result of investments made by successive U.S. Administrations. President Ronald Reagan envisioned the program—the Strategic Defense Initiative (SDI)—as a layered ballistic missile defense (BMD) system that would render nuclear missiles “impotent and obsolete.”11 These layers would have boost, ascent, midcourse, and terminal interceptors, including directed-energy interceptors, providing the United States with more than one opportunity to shoot down an incoming missile.

The United States stopped far short of this goal even though the SDI program generated tremendous technological advances and benefits.12 Instead of a comprehensive layered system, the United States has no boost-phase ballistic missile defense systems and no defense against the advanced ballistic missile threats from China or Russia. The volatility and inconsistency of priority and funding for missile defense by successive Administrations and Congresses—Administrations and Congresses controlled by both major political parties—have yielded a system that is limited both numerically and technologically and incapable of defending against more sophisticated or more numerous long-range missile attacks.

The National Missile Defense Act of 1999 made it U.S. policy to protect the homeland only from a “limited ballistic missile attack.”13 The National Defense Authorization Act (NDAA) for Fiscal Year 2017 dropped the word “limited” even as it continued to focus on ballistic missiles.14 Then the 2020 NDAA made it a matter of policy to rely on nuclear deterrence to defend against “near-peer intercontinental missile threats” and focus on improving missile defense against “rogue states.”15 In the future, as technological trends progress and modern technologies become cheaper and more widely available, North Korean or Iranian ballistic missiles may rival—in sophistication if not in numbers—those of Russia or China. Consequently, the United States must remain aware of how such threats are evolving and be prepared to alter its missile defense posture accordingly.

In January 2019, the Trump Administration published its congressionally mandated Missile Defense Review (MDR), a statement of policy intended to guide the Administration’s missile defense programs. The 2019 MDR addresses the dangerous threat environment that has evolved since the previous MDR in 2010 and recognizes that future missile defense systems must defend against cruise and hypersonic missiles in addition to ballistic missiles.16 The Biden Administration completed its MDR in 2022 but has not yet released the document to the public.

For fiscal year (FY) 2023, the Biden Administration has requested $9.6 billion for the MDA,17 a decrease from the $10.3 billion finally agreed upon for FY 2022.18

Interceptors

Interceptors are one major component of the U.S. missile defense system. Different types of interceptors that respond to different missile threats have been emphasized over the years, and the composition of today’s U.S. missile defense reflects these choices.

While the United States is working to improve its ability to strike down cruise missiles and hypersonic glide vehicles, the primary mission of its fully operational missile defense systems today is to intercept ballistic missiles. Missile defense interceptors are designed to intercept ballistic missiles in three different phases of flight.

• The boost phase extends from the time a missile is launched from its platform until its engines stop thrusting.
• The midcourse phase is the longest and thus offers a unique opportunity to intercept an incoming threat and, depending on other circumstances like the trajectory of the incoming threat and quality of U.S. tracking data, a second shot if the first intercept attempt fails.
• The terminal phase is less than one minute long, occurring as the missile plummets through the atmosphere toward the target, and offers a very limited opportunity to intercept a ballistic missile threat.

Boost-Phase Interceptors. The United States currently has no capability to shoot down missiles in their boost phase. Technologically, boost-phase intercept is the most challenging option because of the very short time during which a missile is boosting, the missile’s extraordinary rate of acceleration during this brief window of time, and the need to have the interceptor close to the launch site.19 This phase, however, is also the most beneficial time to strike. A boosting ballistic missile is at its slowest speed compared to other phases; it is therefore not yet able to maneuver evasively and has not yet deployed decoys that complicate the targeting and intercept problem.

In the past, the United States pursued several boost-phase programs, including the Airborne Laser, the Network Centric Air Defense Element, the Kinetic Energy Interceptor, and the Air Launched Hit-to-Kill missile. Each of these programs was eventually cancelled because of technical, operational, or cost challenges, and the United States has not progressed significantly on any boost-phase program since then.

Midcourse-Phase Interceptors. Intercepting missiles in their midcourse phase offers more time for intercept and presents fewer technological challenges than intercept in the boost phase presents, but it also allows the missile time to deploy decoys and countermeasures that can complicate interception by confusing sensors and radars. The United States deploys two systems that can shoot down incoming missiles in the midcourse phase of flight:

• The Ground-Based Midcourse Defense (GMD) system and
• The Aegis defense system.

The Ground-Based Midcourse Defense system is the only operational system capable of shooting down a long-range ballistic missile headed for the U.S. homeland. It consists of 40 Ground-Based Interceptors (GBIs) at Fort Greeley, Alaska, and four at Vandenberg Air Force Base, California. A GBI consists of a multi-staged rocket booster and an Exoatmospheric Kill Vehicle (EKV), which intercepts the incoming missile with hit-to-kill technology. In September 2021, the MDA “demonstrated the capability to select a 2-stage or 3-stage burn of a Ground Based Interceptor (GBI) booster, which enables an earlier release of the kill vehicle to greatly expand the engagement area and time to counter the inbound threat.”20

To increase the probability of an intercept, the United States has to shoot multiple interceptors at each incoming ballistic missile. At present, because its inventory of interceptors is limited, the United States can shoot down only a handful of ballistic missiles that have relatively unsophisticated countermeasures.

In 2017, Congress approved a White House request to increase the number of GBIs from 44 to 64 to keep up with the advancing ballistic missile threat, particularly from North Korea.21 The MDA intended to produce a Redesigned Kill Vehicle (RKV) to top 20 additional GBIs that would fill the new silos, but this program was canceled in 2019 because of technological difficulties.22 The MDA instead initiated the Next Generation Interceptor (NGI) program to build an entirely new interceptor that would add both capacity and capability to the GMD system. NGIs will begin to fill the 20 empty silos around 2028 and could eventually replace some or all of the existing 44 GBIs. Unlike the GBIs, the NGI will feature multiple kill vehicles, enabling a single NGI to shoot at multiple objects ejected from one incoming missile.23

Contracts to develop the NGI were awarded to Lockheed Martin and a Northrop Grumman–Raytheon team in March 2021.24 The FY 2023 budget request includes $1.766 billion for NGI to support these two competing designs through Critical Design Review in FY 2025.25

The Aegis defense system is a sea-based component of the U.S. missile defense system. It is designed to address the threat of short-range, medium-range (1,000–3,000 kilometers), and intermediate-range (3,000–5,500 kilometers) ballistic missiles. It utilizes different versions of the Standard Missile-3 (SM-3) and SM-6 depending on the threat and other considerations like ship location and quality of tracking data. The Aegis system also has capability against aerial threats and cruise missiles.26 According to the FY 2023 budget submission, the number of BMD-capable Navy Aegis ships should increase to 50 by the end of FY 2023.27 Japan also has several Aegis BMD-capable destroyers and cooperated with the United States to develop the latest SM-3 missile, the SM-3 Block IIA.28

The United States also deploys a land-based version of Aegis, called the Aegis Ashore system, in Romania, and another is nearing completion in Poland. Aegis Ashore sites relieve some of the stress on the naval fleet because BMD-capable cruisers and destroyers are multi-mission and are used for other purposes, such as wartime fleet operations and even anti-piracy operations. These Aegis Ashore sites help to protect U.S. allies and forces in Europe from the Iranian ballistic missile threat.

Aegis BMD will also play a significant role in the development of a missile defense system on the U.S. territory of Guam. Former Commander of U.S. Indo-Pacific Command (INDOPACOM) Admiral Philip Davidson has testified that “the most important action we can take to increase the joint force’s lethality [in the region] is to introduce a 360-degree, persistent, air and missile defense capability on Guam (Guam Defense System (GDS)).”29 Current INDOPACOM Commander Admiral John Aquilino testified in March 2022 that “Guam’s strategic importance is difficult to overstate” and emphasized “the importance of the island for sustaining the joint force as our main operating base and home to 130,000 Americans.”30 The FY 2023 budget request includes a total of $892 million to continue development of an architecture for Guam defense and to begin procurement of needed components, including SM-3, SM-6, and Aegis fire control components.31

In November 2020, the U.S. Navy and the MDA shot down an intercontinental-range ballistic missile using the SM-3 interceptor class Block IIA against an ICBM target.32 The test, FTM-44, was the first step in a plan to use SM-3 Block IIAs as an “underlay” to the GMD system to defend the homeland, with GBIs taking the first shot at an incoming target and SM-3 interceptors taking a second shot if the GBIs miss.33 The MDA had initially planned to test the SM-3 IIA against a more complicated ICBM as the next step. However, the budget request for FY 2023 eliminates funds to pursue the SM-3 IIA as a homeland underlay.34

Terminal-Phase Interceptors. The United States currently deploys three terminal-phase missile defense systems:

• Terminal High Altitude Area Defense (THAAD);
• The Patriot missile defense system; and
• Aegis BMD.

A THAAD battery can shoot down short-range and intermediate-range ballistic missiles inside and just outside of the atmosphere.35 It consists of a launcher, interceptors, the Army Navy/Transportable Radar Surveillance and Control Model 2 (AN/TPY-2) radar, and fire control.36 The system is transportable and rapidly deployable. THAAD batteries have been deployed to such countries as Japan, South Korea, Israel, and the United Arab Emirates (UAE), and the U.S. signed a deal in 2020 to deliver THAAD to Saudi Arabia.37 THAAD was employed successfully to intercept missiles for the first time in the UAE in February 2022.38

Patriot is an air-defense and short-range ballistic missile defense system. A battery is comprised of a launcher, interceptors, AN/MPQ-53/65 radar, an engagement control station, and diesel-powered generator units. The Patriot family of missile defense interceptors has been upgraded over time, from the initial Patriot Advanced Capability-1 (PAC-1) deployed in Europe in 1988 to the PAC-3 configuration deployed around the world today. The most recent Patriot upgrade, the PAC-3 Missile Segment Enhancement, expands the lethal battlespace with an advanced solid rocket motor.39 The system is transportable, and the United States currently deploys it in several theaters around the world.40

Assessment. Interceptor strength is difficult to assess because, while deploying more interceptors to increase capacity or defend more targets is always preferable, deploying more short-range to medium-range interceptors to unprotected locations or increasing interceptor capacity ad infinitum is simply not feasible. Congress provided funding in FY 2022 to procure additional SM-3 Block IIA, PAC-3, and THAAD interceptors.41 The FY 2023 budget would continue this effort for PAC-3 interceptors and continue funding for the eighth THAAD battery, but it would reduce procurement for THAAD and SM-3 IIA interceptors.42

To increase the defended battlespace, the MDA is pursuing the Patriot Launch-on-Remote (THAAD) capability, which integrates the PAC-3 and THAAD systems by enabling a PAC-3 launch using a THAAD AN/TPY-2 radar. Launch-on-Remote is a significant capability that can increase the defended area by spreading out missiles.43 After two failed tests for the capability in 2020, the MDA, in conjunction with the Army, conducted two successful tests early in 2022.44 The Army plans to field this capability “across all Patriot battalions beginning in Fiscal Year 2023.”45

Progress on building a Guam defense system has moved slowly compared to the urgency of the Chinese threat.46 Even though this missile defense system first appeared on the INDOPACOM Unfunded Priorities List in 2019, the President requested and Congress first provided funding for the system only in FY 2022.47 Even so, the $192 million that was appropriated fell far short of the $350 million requested by INDOPACOM for that year.48 However, the FY 2023 budget request includes $892 million “for the Missile Defense Agency, the Army, and the Navy to develop and field missile defense capabilities” that would “augment the existing Terminal High Altitude Area Defense (THAAD) battery currently emplaced on the island…and bolster U.S. military posture in the Indo-Pacific region.”49

The Commander of U.S. Northern Command (NORTHCOM), General Glen VanHerck, recently testified that “[w]hile current BMD capability and capacity is sufficient to defeat a limited ballistic missile attack from a rogue nation, North Korea’s ongoing development of increasingly complex and capable strategic weapons requires the Next Generation Interceptor to be fielded on time or early.”50 The increasing capacity of North Korea’s ballistic missiles to strike the U.S. homeland and North Korea’s ability to deploy decoys cause concern that the rogue state may eventually be able to overwhelm the current GMD system.51

Following a delay in awarding the NGI contract, the program appears to be on track for an initial fielding in 2028 if not 2027.52 NGI will add needed capacity and capability to the GMD system. In addition to accelerating the NGI program, the MDA and Congress continue to support a GMD service life extension program (SLEP) that is intended to maintain the existing fleet through this decade and beyond 2030. Given that NGI will not replace the existing GBI fleet—at least not initially—it is critical that the existing interceptors can remain in service. The GMD system was largely built in the early 2000s, and many parts—including the GBI kill vehicles, boosters, and ground systems—are subject to degradation from aging. The SLEP, for instance, will include the delivery of five new boosters to ensure that the number of interceptors does not decrease, and it is essential that this effort to avoid a decrease in capacity continues.53 The MDA will also need to consider additional NGI purchases after the initial 20 to begin replacing existing GBIs in the 2030s.

In 2019, to strengthen homeland missile defense after the RKV was canceled and before NGI comes online, the Trump Administration proposed the development of an underlay using SM-3 Block IIA and THAAD interceptors. General VanHerck agreed to the value of an underlay in 2021, stating that “an underlayer would give us additional capacity and capability” to address threats to the homeland.54 The MDA had progressed toward this underlay after its successful test of the SM-3 IIA against an ICBM target in 2020, but the Department of Defense (DOD) had not articulated a concept of operations for employing the SM-3 Block IIA and THAAD for homeland defense, including where in the United States those systems could be deployed or how many would be required, as requested by Congress. The budget request for FY 2023 eliminates all funding for the layered homeland defense program.

While the MDA is investing both in the GMD SLEP and the NGI program to ensure defense of the homeland, forgoing a homeland underlay will deprive the homeland of added capacity against an uncertain North Korean threat. The utility of exploring the use of SM-3 and THAAD interceptors for ICBMs can also extend beyond an underlay for the continental United States, as they can work for other missions or defended assets like Hawaii, Alaska, and Guam as well. Using SM-3 and THAAD interceptors to defend against ICBMs could still be advantageous for the United States, but it would require a commitment to move quickly that neither the DOD nor Congress has demonstrated.

Currently, the only interceptor the United States has available to intercept hypersonic missiles is the SM-6.55 To strengthen U.S. capability against maneuverable hypersonic missiles, the MDA is in the early stages of developing the Glide Phase Interceptor (GPI), which is designed to intercept regional hypersonic missiles in their glide phase of flight. In 2021, the MDA awarded Other Transaction Authority (OTA) agreements to Lockheed Martin, Northrop Grumman, and Raytheon to develop design concepts for the GPI.56 For FY 2022, Congress added $39.9 million to the MDA’s requested amount of $247.9 million for hypersonic defense,57 and the FY 2023 budget request includes $225.5 million for the program.58

The Army’s Indirect Fire Protection Capability Increment 2 (IFPC 2) program has been moving very slowly but has seen recent improvement. The IFPC 2 would defend against short-range rockets, artillery, and mortars as well as cruise missiles, against which the United States, as noted, lacks a sufficient defensive capability.59 As a system, IFPC would fill the gap between short-range tactical air defense and ballistic missile defense like PAC-3 and THAAD.

In response to a congressional requirement that it field an interim cruise missile defense capability in response to the increasing cruise missile threat, the Army purchased two Iron Dome batteries manufactured by the Israeli company Rafael.60 Despite prior concerns about integrating Iron Dome as part of an enduring IFPC solution, the Army is preparing the Iron Dome systems for operational deployment and integration into its future missile defense command and control system.61 In 2021, the Army deployed Iron Dome to Guam and conducted a successful simulation to test the system.62 However, no evidence indicates that Iron Dome will be integrated into the Guam defense system that is under development. In September 2021, the Army awarded a contract to Dynetics to develop its own enduring IFPC 2 system, which is scheduled to reach combat capability in FY 2023.63

Overall, the United States has multiple capable interceptors, but there is much room for improvement. The most important step for the near future will be on-time or early delivery of the NGI to ensure protection of the homeland from North Korea and to mitigate the growing threat from China.

Sensors

The sensor component of the U.S. missile defense system is distributed across the land, sea, and space domains and provides the United States and its allies with the earliest possible warning of a launch of enemy missiles in addition to missile tracking and discrimination. These sensors can detect a missile launch, track a missile in flight, and even classify the type of projectile, its speed, and the target against which the missile has been directed. They relay this information to the command and control stations that operate interceptor systems like Aegis (primarily a sea-based system) or THAAD (a land-based system).

Land-Based. On land, the major sensor installations are the upgraded early warning radars (UEWRs), which are concentrated along the North Atlantic and Pacific corridors that present the most direct flight path for a missile aimed at the United States. They include the phased array early warning radars based in California, the United Kingdom, and Greenland that scan objects up to 3,000 miles away.64 Two additional sites—one in Cape Cod, Massachusetts, and the other in Clear, Alaska—have been modernized for use in the layered ballistic missile defense system after facing delays.65 These sensors focus on threats that can be detected in the missile’s boost or launch phase when the release of exhaust gases creates a heat trail that is relatively easy for sensors to detect. A shorter-range (2,000-mile) radar called the Cobra Dane is based in Shemya, Alaska.66

The United States also deploys mobile land-based sensors called AN/TPY-2s. These sensors can be forward deployed for early threat detection or kept in terminal mode to provide tracking and fire control support for the THAAD interceptors.67 Of the United States’ 12 AN/TPY-2 systems, five are forward deployed with U.S. allies.68 The United States plans to field a 13th AN/TPY-2 radar in FY 2025 for service with the eighth THAAD battery.69 In cooperation with the Republic of Korea, the United States deploys a THAAD missile system accompanied by an AN/TPY-2 on the Korean Peninsula.

To fill a gap in missile discrimination capability for tracking North Korean missiles over the Pacific, the MDA is developing the Long Range Discrimination Radar (LRDR) in Northern Alaska to improve coverage in the northern Pacific. The LRDR utilizes the SPY-7 radar, which the MDA will also purchase for the Guam defense system.70 The DOD had also identified the need to develop the Homeland Defense Radar–Hawaii (HDR–H) to fill a tracking and discrimination gap over Hawaii. The Trump Administration’s FY 2021 budget request omitted funding for HDR–H because of budget constraints, as did the Biden Administration’s request for FY 2022. In both years, Congress provided the funding needed to proceed with the radar, and in FY 2022, it mandated that future budget requests must include adequate funding to build and operate the HDR–H by 2028.71 However, the FY 2023 budget request again excludes funding for the HDR–H.72

Sea-Based. There are two types of sea-based sensors. The first is the Sea-Based X-band (SBX) radar, which is mounted on an oil-drilling platform and can be relocated to different parts of the globe as threats evolve.73 SBX is employed primarily in the Pacific. The second radar is the SPY-1 radar system, which is mounted on U.S. Navy vessels equipped with the Aegis Combat System and therefore is able to provide data that can be utilized for ballistic missile missions. The Navy is replacing all SPY-1 radars with the SPY-6 radar, which will have a greater detection range and other advanced capabilities.74

Space-Based. Finally, U.S. missile defense sensors operate in space. From the ultimate high ground, space-based sensors have the potential to detect and track missile launches from almost any location from boost to terminal phase, unlike ground-based radars that are limited in their tracking range.75 The MDA, the U.S. Space Force, and the Space Development Agency (SDA) all control aspects of the space missile defense sensor system.

The oldest system that contributes to the missile defense mission is the Defense Support Program (DSP), a constellation of satellites that use infrared sensors to identify heat from booster and missile plumes to detect an initial launch. The DSP satellite system has gradually been replaced by the Space-Based Infrared Radar System (SBIRS) to improve the delivery of missile defense and battlefield intelligence.76 For instance, SBIRS can scan a wide swath of territory while simultaneously tracking a specific target, making it a useful means for observing tactical, or short-range, ballistic missiles.77

The Space Force launched the sixth and final SBIRS satellite in August 2022.78 The Air Force originally planned to launch eight SBIRS satellites, but because of congressional funding delays, it decided to end production of SBIRS early and move on to development of its replacement, the Next-Generation Overhead Persistent Infrared (Next-Gen OPIR) satellite, in 2017.79 The seventh and eighth SBIRS satellites will be switched to Next-Gen OPIR satellites, the first of which is to be delivered “no later than FY 2025.”80 The Next-Gen OPIR satellites are designed to be more survivable against cyber and electronic attacks.

The MDA also has developed and deployed Space-based Kill Assessment (SKA) sensors on commercial satellites.81 SKA uses a network of infrared sensors to provide a hit and kill assessment of homeland defense intercepts. After several years of successful testing of SKA sensors in orbit, the FY 2023 budget supports integrating SKA into the homeland defense system.82

The United States is developing a system of satellites capable of providing global detection, tracking, and discrimination of any missile launch. Dating back as far as President Reagan’s Strategic Defense Initiative, successive Administrations have called for a proliferated layer of sensing satellites in space to track the flight of any type of missile—not just ballistic—from birth to death. A layer of space-based sensors can be particularly useful in tracking hypersonic vehicles, which fly at lower altitudes than ballistic missiles and can maneuver during flight. The DSP and SBIRS systems were designed for ballistic missiles and can lose track of missiles flying at lower altitudes. Since many new threats are not flying on ballistic trajectories, Congress has been paying close attention to development of this space sensor layer.

Beginning in 2009, the MDA operated two Space Tracking and Surveillance System-Demonstrators (STSS-D) satellites in an effort to demonstrate this capability to track ballistic missiles that exit and reenter the Earth’s atmosphere during the midcourse phase.83 Data obtained by those demonstration satellites were used to provide risk reduction to support future space trackers. Both satellites were decommissioned in March 2022.84 Today, the SDA, in conjunction with the MDA, is developing a space Tracking Layer of satellites proliferated in Low-Earth Orbit (LEO) as part of the SDA’s National Defense Space Architecture. According to the SDA:

Once fully operational, the SDA Tracking Layer will consist of a proliferated heterogeneous constellation of Wide Field of View (WFOV) space vehicles (SVs) that provide persistent global coverage and custody capability combined with the Missile Defense Agency (MDA) Hypersonic and Ballistic Tracking Space Sensor (HBTSS) Medium Field of View (MFOV) SVs that provide precision global access capability.85

Once deployed, the Tracking Layer will be able to detect, track, and discriminate among any types of missile launch throughout the entirety of the missile’s flights, including both hypersonic glide vehicles and dimmer ballistic missile targets. The SDA is also exploring the ability of space sensors to provide fire control information directly to weapon platforms like THAAD or Aegis (as opposed to the data going through a ground station).

In FY 2022, Congress provided $256 million to the MDA for the HBTSS. In 2021, the MDA awarded contracts to Northrop Grumman and L3Harris to develop HBTSS prototypes, which are on track to launch in FY 2023. The budget request for FY 2023 includes $89.2 million for this effort.86 Congress also added $550 million in FY 2022 for the SDA’s tracking layer. The first eight satellites as part of Tranche 0 are projected to launch in 2023.87 The SDA is also working to award a contract for Tranche 1 satellites to launch in 2025.88

Assessment. Senior defense leaders have stated repeatedly that deploying sensor satellites to space to track missiles from the high ground throughout their entire flight is the best way to advance sensor capability. According to Admiral Charles Richard, Commander of U.S. Strategic Command (STRATCOM):

Future space-based sensors may be able to provide birth-to-death detection, tracking, and discrimination of hypersonic glide vehicle, cruise missile, and ballistic missile threats globally. These abilities cannot be fully achieved with the current or future terrestrial-based radar architecture due to the constraints of geography and characteristics of future missile threats.89

Initially, the space-based sensor program was plagued by insufficient funding requests and bureaucratic infighting over whether the SDA or the MDA would develop the HBTSS.90 Since then, clear roles for the SDA and MDA have been defined, contracts for the HBTSS have been awarded, and the SDA’s Tracking Layer has progressed steadily. A strong assessment of missile defense sensing capabilities will depend on progress made on the space-based sensor effort, especially in view of commanders’ urgent need for improved missile tracking as well as the technological challenges associated with developing a sensor that can perform in LEO.91

Development of land-based sensors to fill the missile discrimination capability gap over the Pacific has progressed slowly. Development of the LRDR has been delayed by at least a year.92 The HDR-H project continues to face an uncertain future: Congress provides appropriations for the program, but the DOD does not include it in its budget request despite explicit congressional direction to do so. This way of funding a program that was originally proposed to fill a discrimination gap over Hawaii is problematic, as the DOD and Congress have never resolved their differences over the need for this capability.

Improved sensor capabilities are also critical to addressing the cruise missile threat to the homeland. As noted previously, the United States has no dedicated missile defense system to counter this threat. Due to their low-trajectories, cruise missiles are more difficult to detect and track than are ballistic missiles. Russia’s ability to strike key strategic nodes in the U.S. homeland from its own territory is of particular concern. To address the cruise missile threat, General VanHerck has emphasized improving domain awareness, because early identification of a threat allows for options like left-of-launch operations or diplomacy to avoid having to shoot down cruise missiles inside the U.S.93

The MDA included $11 million in the FY 2023 budget request (down from $14 million in FY 2022) to develop an architecture for cruise missile defense of the homeland. In 2021, General VanHerck requested funding for a new elevated sensor to help detect cruise missiles aimed at Washington, D.C.94 The NORTHCOM unfunded priorities lists for both FY 2022 and FY 2023 include additional funding for a cruise missile defense homeland kill chain demonstration.95 Developing a capability to detect, track, and eventually intercept a conventional cruise missile attack will be critical to denying adversaries the ability to hold the homeland at risk below the nuclear threshold.

The Next-Gen OPIR program appears to remain on schedule after early delays, and the FY 2023 budget request continues to fund the program. It also includes funding for several LEO and Medium Earth Orbit satellites to enhance missile warning capabilities.96 The Army is also progressing quickly on development of the Lower-Tier Air and Missile Defense System radars that will provide 360-degree threat coverage for PAC-3 and other regional missile defense batteries; the current Patriot radar can scan only one-third of the sky at a time.97

The space-sensor project is now on track compared to previous years. It is important that land-based radar coverage moves forward to stabilize the future sensor architecture.

Command and Control

Command and control of the U.S. ballistic missile defense system requires bringing together data from U.S. sensors and radars and relaying those data to interceptor operators so that they can destroy incoming missiles directed against the U.S. and its allies. The operational hub of missile defense command and control is the Joint Functional Component Command for Integrated Missile Defense (JFCC IMD), a component of STRATCOM housed at Schriever Air Force Base, Colorado. JFCC IMD brings together Army, Navy, Marine Corps, Space, and Air Force personnel and is co-located with the MDA’s Missile Defense Integration and Operation Center (MDIOC). This concentration of leadership from across the various agencies helps to streamline decision-making for those who command and operate the U.S. missile defense system.98

Command and control of the GMD system to defend the homeland utilizes the Ground-based Midcourse Defense Fire Control (GFC) system, which consists of a suite of hardware, software, and personnel located in Fort Greely, Alaska, and Vandenberg Air Force Base, California.99 The system involves collecting data on missile movement from sensors and radars to inform the launch of GBIs.

Once a missile is launched, data from the U.S. global network of sensors and radars travel through secure satellite communications and ground-based redundant communications lines to the Command Launch Equipment (CLE) software that can task GBIs to fire at the incoming missile. Then, once the NORTHCOM Commander—who becomes the supported commander during GMD execution—in consultation with the President has determined the most effective response to a missile threat, the CLE fire response option is relayed to the appropriate GBIs in the field.100 When the selected missiles have been fired, they maintain contact with In-Flight Interceptor Communications System (IFICS) Data Terminals (IDTs) to receive updated flight information that helps to guide them to their target.101

To prepare for and execute GMD operations, the NORTHCOM Commander can also utilize situational awareness data from the Command and Control, Battle Management and Communication (C2BMC) system. Through its software and network systems, C2BMC helps to process and integrate sensor information to provide a more complete picture of the battlespace.102 The GMD Fire Control system acts as the primary decision aid for GMD execution, and the C2BMC system provides integrated battlefield awareness information before and during GMD operations.103 It also provides information to other missile defense systems like THAAD and Patriot. Dozens of C2BMC workstations are distributed throughout the world at U.S. military bases.

C2BMC has undergone multiple technical upgrades (called spirals) since 2004 to bring more missile defense elements into the network. In 2019, the MDA completed an upgrade that will help to expand Aegis missile defense coverage by enabling Aegis Weapons Systems to engage on remote.

Regional missile defense systems like THAAD, PAC-3, and Aegis are equipped with their own individual fire control systems to control the launch of their interceptors. The C2BMC system can also provide tracking information to individual missile defense batteries from other regional sensors. Aegis BMD systems have onboard control governed by the Aegis Combat System, and they can provide their sensor data to the GMD system through C2BMC.104

C2BMC connects sensors and shooters around the world to a global network, but there is no comparable system to link sensors and shooters in a single region. The Army is developing the Integrated Air and Missile Defense (IAMD) Battle Command System (IBCS) to provide this capability. Once fielded, IBCS would connect all sensors and shooters in a region to a single fire control network.105 Like IFPC, IBCS would also link defenses against smaller threats with ballistic missile defense.

Assessment. A strong global command and control system is critical to missile defense because linking information from sensors can increase domain awareness and the time available to engage a target, thereby improving the probability of intercept. In addition, according to General VanHerck, “[g]lobal all-domain awareness will generate a significant deterrent effect by making it clear that we can see potential aggressors wherever they are, which inherently casts doubt on their ability to achieve their objectives.”106 This concept is especially important in dealing with cruise missile threats to the homeland, against which the U.S. has no comprehensive interceptor capability.

Continuing to upgrade the C2BMC will remain critical to increasing the integration of missile defense elements across the world and therefore improving chances of intercept. For instance, it was revealed in 2021 that the MDA provided U.S. Indo-Pacific Command with a hypersonic missile defense capability, largely as a result of C2BMC improvements that allow sensors to see the threat sooner.107 The MDA is nearing completion of another upgrade to incorporate the LRDR into C2BMC after a delay.108 It also has linked C2BMC to the Army’s IBCS, and the next round of upgrades will further integrate those systems as well as enhance the threat data provided to the GMD system.109

The United States will need a more advanced command and control capability as global missile threats shift to include cruise and hypersonic missiles in addition to ballistic missiles. The DOD is currently developing a Joint All Domain C2 (JADC2) system to integrate non-compatible sensors across all domains into a single network so that it can respond to the complex threat more efficiently. Missile defense command and control will strengthen as the services begin to field JADC2 capabilities.

In addition, NORTHCOM and the North American Aerospace Defense Command have conducted a series of Global Information Dominance Experiments (GIDE) that “provid[e] combatant commanders, intelligence and operations directors, and other participants at multiple sites with a shared, customizable, and near real-time data set” by collecting and integrating information from multiple sensors needed for decision-making and sending that information to commanders quickly.110 Sensor information can tend to exist in stovepipes, and if it is not integrated, the result can be failure to detect a threat.111 GIDE also uses artificial intelligence and machine learning cues to ensure that the commander receives a full data picture.112

IBCS will also provide an important improvement in regional missile defenses. The system will link all missile defense sensors and interceptors to one fire control center, as opposed to today’s more stovepiped approach in which each unit operates its co-located sensor and launcher independently. By permitting air and missile defenses to function as a joint kill web rather than as a linear kill chain, IBCS will be able to determine the best shooter to take down an incoming missile, in turn increasing the defended battlespace.

After an initial multi-year delay due to technical issues, the Army has awarded a production contract for IBCS to Northrop Grumman, and the program is now on its new schedule for full production by the end of 2022.113 Advancements underway in missile defense command and control will become increasingly necessary to enable defense against the growing missile threat.

Conclusion

By successive choices of post–Cold War Administrations and Congresses, the United States does not have in place a comprehensive set of missile defense systems that would be capable of defending the homeland and allies from robust ballistic missile threats. U.S. efforts have focused on a limited architecture that protects the homeland and on deploying and advancing regional missile defense systems.

Although the United States has in place multiple types of capable interceptors, a vast sensor network, and a command and control system, many elements of the missile defense system need to be improved to defend against today’s threat more efficiently. At the same time, the development of missile threats, both qualitative and quantitative, is outpacing the speed of missile defense research, development, and deployment to address those threats. Senior leaders continue to stress the importance of U.S. missile defense, but if the nation is to realize the strategic benefits that missile defense provides, Congress must ensure that the funding of critical programs like NGI, space sensors, and JADC2 is commensurate with that importance.