Issue Briefs

To Defeat Hypersonic Weapons, Pentagon Aims To Build Vast Space Sensor Layer

By Loren Thompson

February 6th 2020

The Trump Administration is pursuing a series of secret military space projects that collectively will cost tens of billions of dollars. At least one of those projects is too big to hide: a Space Sensor Layer that would place hundreds of satellites in low earth orbit (LEO) to track hostile hypersonic missiles, and many ballistic threats too.

The Pentagon has been working for decades on methods of intercepting ballistic missiles aimed at U.S. forward-deployed forces, overseas allies, and the American homeland. Longer-range missiles typically are harder to intercept than shorter-range missiles because they move faster, and the ones with intercontinental reach are usually equipped with penetration aids (like decoys) to elude defenders.

What all ballistic missiles have in common, though, is that they follow a stable trajectory that makes their approximate destination easy to estimate. Now a new danger has arisen that threatens to negate the huge investment Washington has made in missile defenses: hypersonic missiles that glide through the atmosphere and maneuver unpredictably at speeds of a mile per second or faster.

Because longer-range ballistic missiles often move faster than the hypersonic systems that Russia and China are developing, the Pentagon already has interceptor systems that potentially could destroy them. What it lacks is a sensor network for tracking the missiles and guiding interceptors to their vicinity.

That’s why the Space Sensor Layer is vital. The current approach to tracking ballistic missiles is for space-based infrared satellites in geosynchronous orbit to detect launches, and then cue terrestrial radar systems to follow them through their trajectories. But that won’t work with hypersonic glide weapons because they fly too low—generally within the atmosphere. Due to the curvature of the earth, surface radars won’t see them coming until they are only seconds away.

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The views and opinions expressed in this issue brief are those of the author.

Loren B. Thompson is a Senior Adviser at GPI, Chief Operating Officer of the non-profit Lexington Institute and Chief Executive Officer of Source Associates, a for-profit consultancy. Prior to holding his present positions, he was Deputy Director of the Security Studies Program at Georgetown University and taught graduate-level courses in strategy, technology and media affairs at Georgetown. He has also taught at Harvard University’s Kennedy School of Government. Mr. Thompson holds doctoral and masters degrees in government from Georgetown University and a bachelor of science degree in political science from Northeastern University.