Raytheon defines first principles for building a space sensor layer

By Loren Thompson*

The U.S. Department of Defense is contemplating construction of the most ambitious space constellation in history to defeat the threat posed by hypersonic weapons.

Called the Space Sensor Layer, the constellation would be a “system of systems” linking dozens to hundreds of satellites in low-earth orbit with other satellites in higher orbits

The impetus for the Space Sensor Layer arises from the realization that the United States currently has no real defense against long-range hypersonic weapons, missiles that maneuver unpredictably at five times the speed of sound, or faster.

The Pentagon has spent over $100 billion across several decades developing the ability to track and intercept long-range ballistic threats such as Russian ICBMs. It isn’t easy. But ballistic weapons at least have predictable trajectories, enabling defenders to focus their efforts.

Hypersonic weapons of the kind Russia and China are thought to be developing move at similar speeds but can maneuver in almost any direction as they approach their targets. There is no way of knowing what their ultimate destination might be.

The Pentagon’s Missile Defense Agency, working in concert with the Space Force’s development agency and the Defense Advanced Research Projects Agency (DARPA), has fashioned a plan to continuously track hypersonic threats no matter where they originate, and then quickly hand off targeting information to “shooters” capable of negating the danger.

Developing appropriate means of interception, either kinetic or non-kinetic, is a separate issue. But the most immediate challenge is simply being able to detect and track the threat, and that’s what the Space Sensor Layer will be designed to do.

Several companies are competing to lead the industry team that builds the new constellation and integrates it with preexisting sensors already in the joint force. This week I had the opportunity to discuss the challenge with one of the experts architecting the solution that Raytheon RTX +3.3% Technologies (a contributor to my think tank) will propose.

There are so many moving pieces to the Space Sensor Layer that it seems dozens of companies might end up having a role. But only one team will win the contract to design the overall architecture, and that’s the prize for which Raytheon’s Intelligence & Space unit is aiming.

What’s striking about the vision that was described to me is that despite all the technical arcana associated with space operations, the core principles are quite similar to concerns that arise in standing up any military mission. The system must be fast, it must be accurate, it must be resilient, etc.

Here are the four core principles that stood out for me in hearing how Raytheon Technologies would design a solution to this unique military challenge.

Coverage. The current U.S. system for tracking ballistic threats cannot cope with weapons that maneuver unpredictably over vast distances. While missile warning satellites in geosynchronous orbit and surface radars on land and at sea can make an important contribution to the mission, a proliferated constellation of dozens to hundreds of satellites will be needed in low-earth orbit to reliably track incoming weapons. These satellites will need to be linked across multiple orbital planes to afford continuous, comprehensive coverage of all potential threats. There is also some discussion of putting spacecraft in medium-earth orbit, at a similar altitude as GPS satellites, to increase the field of view for trackers.

Accuracy. The appeal of low-earth orbit is that satellites are closer to attacking weapons and thus can generate target-quality tracks. Satellites in geosynchronous orbit are too far away to do that. But satellites in lower orbit are moving at thousands of miles per hour relative to the earth’s surface and have a limited field of view, so they must be proliferated and crosslinked to maintain a track—otherwise the track will be lost as the threat disappears over the horizon. The low-earth satellites must be sufficiently numerous so that at least two satellites can see an incoming weapon at any given time, providing the kind of three-dimensional view necessary for accurate characterization of the threat’s position and velocity. This task may need to be performed against hundreds of incoming weapons at the same time.

Speed. The current approach to collecting target information from space sensors is to transmit it to ground stations for processing, from whence it is then sent to shooters who can intercept the threat. But that takes time. Given the speed of hypersonic weapons and the uncertainty about their destinations, the Space Sensor Layer will need to reduce latency by doing most information processing in orbit, fusing inputs from multiple spacecraft, and then sending details directly to shooters. That presumably increases the complexity of satellites, but it is the most effective way to compress the “kill chain.”

Resilience. Capable attackers would probably try to degrade the performance of the Space Sensor Layer to assure their weapons penetrate defenses. The architecture must be highly resilient against such efforts by using measures such as hardening and redundancy so that the potential loss of some assets does not compromise the overall performance of the system. Here too, proliferation and cross-linking are crucial factors, as is the integration of satellites in low-earth orbits with those in higher orbits or on the earth’s surface. And it isn’t enough to just protect the satellites; the communications links and ground stations must also be resilient against both kinetic and non-kinetic (like cyber) attack.

As if all this were not enough, the defense department wants the Space Sensor Layer to be affordable and rapidly fielded. DARPA’s Blackjack initiative to adapt commercial-space business practices to the defense mission could be useful in that regard, because commercial spacecraft typically cost less than military spacecraft and field much faster. Raytheon has its own ideas on how dozens or hundreds of sensing satellites might be made affordable, but recognizes there is an urgency attaching to the mission that dictates the earliest feasible operational date.

The company believes this is all doable, and is conducting tradeoffs to compare sensor options, constellation configurations, algorithm functionality and the like. It has a great deal of experience in performing such trades, as do some of its competitors. If the Space Sensor Layer comes to fruition, it will likely generate significant spinoff benefits because nobody has done anything like this ever before.

*Loren Thompson is a Senior Contributor at Aerospace & Defense

Source: forbes.com

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