Authored by Arjun Sreekumar, and Pravin Pradeep
In a world rapidly advancing in missile technology and arms control challenges, nations are increasingly fortifying their arsenals with sophisticated weaponry such as hypersonic glide vehicles (HGV), scramjet-powered cruise missiles, multiple independently targetable reentry vehicle (MIRV), and anti-satellite (ASAT) systems. These state-of-the-art threats, characterized by their very high speeds and unpredictable paths constrained by the Earth’s geometry, are testing the limits of existing missile defense frameworks. Recent developments highlight significant advancements, such as Russia’s deployment of the Kh-47M2 Kinzhal in Ukraine, alongside their ongoing development of the Avangard and Tsirkon hypersonic missile programs. Similarly, China is advancing its capabilities with a new HGV, and ballistic missiles equipped with MIRV technology, notably the DZ-ZF and the Julang-3, respectively. The latter is designed to deliver multiple warheads to different targets independently, complicating missile defense strategies. These developments, along with active hypersonic programs in North Korea and Iran, underscore the crucial need for robust, adaptive missile defense systems to maintain national security in an increasingly complex global threat landscape.
However, the development and deployment of these hypersonic weapons come with significant challenges and limitations. Technical hurdles such as managing large thermal gradients, navigating aerodynamic boundary layer transitions, and the lower efficiency of ramjets at higher Mach numbers pose complex engineering problems. Material supply chain issues, particularly China’s growing control over critical resources like Niobium, further complicate production. Additionally, the superheated ionized plasma that envelops these missiles at high speeds can disrupt communications and navigation, diminishing their operational effectiveness. These intrinsic challenges have sparked debates about the strategic value of investing heavily in hypersonic technologies, with some arguing that such focus may inadvertently divert resources from developing more tactically and strategically advantageous weapons.
There are several terrestrial and sea-based systems for missile tracking including the Long-Range Discrimination Radar (LRDR) in Alaska, the Upgraded Early Warning Radars (UEWRs), the Cobra Dane radar and the sea-based SPY-1 radar systems installed on the US Ticonderoga-class cruisers and Arleigh Burke-class guided missile destroyers. Perhaps the most advanced sensor is the LRDR, which is currently being transitioned to the U.S. Space Force. This S-Band radar system is designed to provide precise discrimination between warheads and decoys in the incoming threat cluster, thereby conserving excessive release of interceptors. The UEWRs operate in the Ultra High Frequency (UHF) band and whilst they have a range of up to 3,000 miles, they do not provide quality threat discrimination. The Cobra Dane radar system primarily provides tracking and classification during the mid-course phase of missile flight. However, these land and sea-based islands of sensors, when supplemented with a layered space-based surveillance network will help militaries respond more effectively against ballistic and hypersonic weapons.
The U.S. Department of Defense (DoD) is substantially investing in developing an advanced sensor architecture, with significant efforts led by the Space Development Agency (SDA) and Space Systems Command (SSC). This initiative is focused on expanding the network of space-based sensors, especially in low Earth orbit (LEO), to improve the resilience and scope of missile detection and tracking systems. At the heart of this initiative are pivotal programs like the Resilient Missile Warning/Missile Tracking, Hypersonic and Ballistic Tracking Space Sensor, and Next Generation Overhead Persistent Infrared. These initiatives are crucial in integrating elevated sensors into a comprehensive missile defense network that consistently monitors threats from their launch to impact.
The evolution of missile defense strategies highlights the growing necessity for sophisticated sensing architectures. Modern defenses are increasingly dependent on high-altitude sensors, which offer detailed and rapid assessments of missile trajectories—crucial data for accurate fire control. However, positioning these sensors, particularly in LEO, introduces new vulnerabilities, including susceptibility to electronic disruptions and space debris. Addressing these issues requires a diversified strategy that involves deploying sensors across various orbits and incorporating supplementary assets like airborne sensors, particularly in strategically significant areas such as the Indo-Pacific. Moreover, advances in processing power, network capabilities, and sensor integration are critical to ensure precise missile tracking, manage environmental interference, and to counter advanced evasion techniques.
Creating missile tracking systems requires highly sensitive sensors capable of detecting and accurately tracking hypersonic and ballistic missile paths. The U.S. has historically utilized infrared sensors on space-based platforms, prized for meeting stringent size, weight, power, and cost (SWaP-C) criteria while effectively identifying the thermal signatures of missiles. Despite ongoing improvements in resolution, sensitivity, and cost-effectiveness, these sensors face difficulties in tracking advanced missile threats beyond the initial boost phase. As the infrared signatures of hypersonic weapons diminish, distinguishing them against complex terrestrial and celestial backdrops becomes harder.
Efficient missile tracking requires a delicate balance in sensor design—expanding the field of regard (FOR) to reduce the number of necessary satellites while ensuring the sensors themselves can handle the increased demand. Techniques such as mechanical slewing, which enhance coverage, introduce additional mechanical complexities. Innovations in core technologies such as large-format focal plane arrays (FPAs) significantly enhance the capabilities of missile defense systems. These FPAs increase the field of view without sacrificing resolution, which is crucial for effectively monitoring smaller, less distinct targets across vast distances. This technological advancement supports the deployment of both static wide-field-of-view (WFOV) sensors, which are optimal for constant, broad area surveillance, and dynamic medium-field-of-view (MFOV) sensors, tailored for more focused tracking and precise fire control tasks. Additionally, the integration of advanced processing techniques, including artificial intelligence (AI), further refines the data analysis, enabling quicker and more accurate decision-making in missile tracking and interception.
Simultaneously, exploring alternative sensing modalities, such as hyperspectral and radiofrequency (RF) sensors, provides a complementary approach to traditional infrared sensing. Hyperspectral sensors, for instance, capture a broader spectrum of electromagnetic data, offering unique insights into missile plumes and other related signatures that might not be visible in the infrared spectra. RF sensors add another layer of detection capability by propagating through inclement weather conditions for velocity data, and tracking radio emissions from missile launches, providing a different method of engagement that can be particularly effective in congested or contested environments. Together, these alternative sensors expand the scope of detection and analysis, enhancing the robustness and versatility of missile defense architectures.
The DoD is pushing forward with a multi-layered orbital defense architecture that spans LEO, medium Earth orbit (MEO), geosynchronous orbit (GEO), and highly elliptical orbit (HEO), leveraging the unique advantages of each to mitigate their individual limitations. For instance, sensors in LEO are advantageous due to their quick deployment and cost-effectiveness, yet they are hindered by shorter operational lifecycles and limited persistence. MEO satellites provide extensive coverage and enhanced stability, but this comes at the expense of requiring bulkier, more expensive components that must be fortified against radiation. Conversely, satellites in GEO and HEO enable focused coverage over distinct global areas using fewer satellites, albeit at increased costs and with more stringent reliability requirements.
Additionally, an important logistical consideration for these higher-orbit satellites is the need for robust communication pathways to transmit data back to Earth. This often necessitates the development of an inter-satellite network or integration with an existing communications satellite network. This tiered approach also facilitates the strategic deployment of constellations, including low-inclination LEO satellites for regional coverage, while deploying highly inclined LEO satellites to ensure global coverage. Additionally, satellites in a MEO-based equatorial plane are specifically arranged to maintain persistent surveillance over strategically significant areas like the Indo-Pacific region. This configuration is further complemented by a constellation in HEO, designed to enhance coverage of both the equatorial zones and the polar regions, optimizing coverage and cost-efficiency in missile defense architecture.
Complementing these space-based systems, airborne sensors can plug gaps in providing continuous surveillance capabilities unbound by orbital mechanics. Today, advanced fifth-generation fighters like the F-35 have enhanced this capability by transmitting fire control-quality data to ground-based missile defense systems. While these airborne assets do not offer uninterrupted coverage and may be redirected for various operational needs, their integration into broader missile defense frameworks, including unmanned systems like high-altitude long endurance (HALE) and medium-altitude long-endurance (MALE) platforms, significantly enhances overall tracking capabilities. Ongoing development of operational doctrines and enhancement of communication links are crucial to fully integrating these airborne sensors into a comprehensive missile tracking architecture, maximizing their strategic value.
As adversaries field more potent hypersonic weapons and advanced ballistic missiles, the multi-orbit, multi-sensor approach will become the new baseline for detection, discrimination, and tracking. Scores of orbiting sensors are harder to disrupt and offer considerable tactical redundancy. They provide better discrimination to make more accurate intercepts and preserve interceptor inventories. If militaries can evolve and execute a cohesive long-term vision that focuses not only on increasing the number of eyes in space, but also integrating space-based, terrestrial, aerial and maritime sensing assets, missile defense would advance to a new benchmark.
