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Congressional Research Service
lnforrning the legislative debate since 1914
Updated May 15, 2025
Hypersonic Missile Defense: Issues for Congress
The Missile Defense Agency (MDA) and Space
Development Agency (SDA) are currently developing
elements of a missile defense system that may be able 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 China likely fielded
hypersonic weapons as early as 2020.
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 I. 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/20 19/04/06/
gliding-missiles-that-fly-faster-than-mach-5-are-coming.
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.
The Proliferated Warfighter Space
Architecture
According to SDA, the PWSA, formerly known as the
National Defense Space Architecture, aims to be a resilient
layered network of military satellites and supporting
elements, 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 GPS-independent positioning, navigation,
and timing; 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 provide global coverage.
Tracking Layer
SDA states that 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 $108.7
million for Tranche 0 tracking activities in FY2025 and
$1.7 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. 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 $76 million for HBTSS in FY2025. A
March 2025 MDA and U.S. Navy test demonstrated that
HBTSS data could detect, track, and perform a simulated
engagement of a maneuvering hypersonic target.
The Space Force's Space Systems Command (SSC) is
developing a third set of tracking satellites called Resilient
Missile Warning Missile Tracking - Medium Earth Orbit
(MEO). According to SDA, the MEO satellites will add
low-latitude coverage and track custody and enhance
resilience in the nation's missile defense architecture. The
Space Force requested $846.3 million for Resilient Missile
Warning Missile Tracking - MEO in FY2025.
In 2022, the Space Force established a Combined Program
Office to coordinate missile warning and tracking efforts,
including SDA's PWSA, MDA's HBTSS, and SSC's MEO
satellites.
Transport Layer
SDA has stated that the PWSA's transport layer, which is
intended to connect the tracking layer to interceptors and
other weapons systems on the ground, will enhance
several mission areas including missile defense. According](ViewImageLocal?handle=hein.crs/hyscnmsedf0001&div=1&collection=&method=preview&ext=.png&size=3)