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Congressional Research Service
informing the legislative debate since 1914
Updated August 21, 2023
Hypersonic Missile Defense: Issues for Congress
The Missile Defense Agency (MDA) and Space
Development Agency (SDA) are currently developing
elements of a hypersonic missile defense system to defend
against hypersonic weapons and other emerging missile
threats. These elements include the tracking and transport
layers of the Proliferated Warfighter Space Architecture
(PWSA) and various interceptor programs. As MDA and
SDA continue to develop these systems, Congress may
consider implications for oversight and defense
authorizations and appropriations.
Background
Hypersonic weapons, like ballistic missiles, fly at speeds of
at least Mach 5, or roughly 1 mile per second. Unlike
ballistic missiles, hypersonic weapons do not follow a
ballistic trajectory and can maneuver en route to their
target. Russia reportedly fielded its first hypersonic
weapons in December 2019, while some experts believe
that China fielded hypersonic weapons as early as 2020.
The United States is not expected to field hypersonic
weapons until the end of FY2023. (For an overview of
hypersonic weapons programs in Russia, China, and the
United States, see CRS Report R45811, Hypersonic
Weapons: Background and Issues for Congress, by Kelley
M. Sayler.)
The maneuverability and low flight altitude of hypersonic
weapons could challenge existing detection and defense
systems. For example, most terrestrial-based radars cannot
detect hypersonic weapons until late in the weapon's flight
due to line-of-sight limitations of radar detection. This
leaves minimal time for a defender to launch interceptors
that could neutralize an inbound weapon. Figure 1 depicts
the differences in terrestrial-based radar detection timelines
for ballistic missiles versus hypersonic weapons.
Figure 1. Terrestrial-Based Detection of Ballistic
Missiles vs. Hypersonic Weapons
Source: CRS image based on an image in Gliding missiles that fly
faster than Mach 5 are coming, The Economist, April 6, 2019,
https://www.economist.com/science-and-technology/2019/04/06/
gliding-missiles-that-fly-faster-than-mach-5-are-coming.
U.S. defense officials have stated that both existing
terrestrial- and space-based sensor architectures are
insufficient to detect and track hypersonic weapons; former
Under Secretary of Defense for Research and Engineering
Mike Griffin has noted that hypersonic targets are 10 to 20
times dimmer than what the U.S. normally tracks by
satellites in geostationary orbit.
Prohiferated Warfighter Space
Arch tectu re
SDA developed the PWSA, formerly known as the National
Defense Space Architecture, to unify and integrate next
generation capabilities across [the Department of Defense
(DOD)] and industry. The PWSA aims to be a single,
coherent proliferated space architecture with seven layers,
which include the data tracking and transport layers
depicted in Figure 2 and discussed below. Other layers
include the custody layer to support the targeting of mobile
ground assets; the battle management layer to provide
space-based command and control; the navigation layer to
provide alternate positioning, navigation, and timing for
potential GPS-denied environments; the deterrence layer
to detect potentially hostile actions in deep space; and the
support layer to facilitate satellite operations for the other
PWSA layers. Once fully fielded, the PWSA is to include
550 satellites and provide full global coverage.
Tracking Layer
The tracking layer is to provide global indications,
warning, tracking, and targeting of advanced missile
threats, including hypersonic missile systems. As part of
this layer, SDA is developing an architecture of Wide Field
of View (WFOV) satellites, which are to eventually provide
global coverage. SDA requested $106.7 million for Tranche
0 tracking activities in FY2024 and $1.3 billion for Tranche
1 tracking activities (also known as Resilient Missile
Warning Missile Tracking - Low Earth Orbit).
Working in tandem with the SDA's tracking satellites will
be the Hypersonic and Ballistic Tracking Space Sensor
(HBTSS), previously known as the Space Sensor Layer,
which is being developed by MDA in collaboration with
SDA and the U.S. Space Force. HBTSS is to provide more
sensitive, but more limited (or Medium Field of View
[MFOV]) coverage, compared to WFOV. For this reason,
WFOV is intended to provide cueing data to HBTSS, which
could then provide more specific, target quality data to a
ground-based interceptor. MDA requested $109.5 million
for HBTSS in FY2024.
Section 1682 of the FY2020 NDAA (P.L. 116-92) tasks the
director of the Missile Defense Agency to develop a
hypersonic and ballistic missile tracking space sensor
payload. Section 1645 of the FY2021 NDAA (P.L. 116-
283) affirms the MDA director's responsibility for the
development and procurement of the sensor payload-in
coordination with the director of SDA-through, at
minimum, fiscal year 2022. Section 1645 additionally](ViewImageLocal?handle=hein.crs/govempj0001&div=1&collection=&method=preview&ext=.png&size=3)
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