Study: Combine Missile Warning, Tracking Constellations Into One Multi-Orbit System

Air Force Secretary Frank Kendall has made missile warning and tracking a priority of his tenure, and agencies across the Pentagon are working on a number of efforts to handle that mission from space.

But instead of relying on a less coordinated approach, one that forces programs to compete for funds, the Defense Department—and particularly the Space Force—would be better served by integrating their efforts into one multi-orbit system, a new study from AFA’s Mitchell Institute for Aerospace Studies recommends.

The issue is especially urgent because of the continued proliferation of new kinds of missiles, said the study’s author, Christopher Stone, during a virtual event June 7. Technologies such as hypersonic weapons and fractional orbital bombardment systems exploit gaps in the U.S.’s current missile tracking infrastructure so that the weapons can’t be tracked completely by radars on the ground.

Meanwhile, the Space Based Infrared System, flying in highly elliptical and geosynchronous Earth orbits, provides good missile warning, Stone said, but lacks the fidelity for persistent tracking.

Persistently tracking missiles from the moment of their launch to their landing is crucial, said Col. Miguel A. Cruz, commander of the Space Force’s missile warning delta, Space Delta 4, during the virtual event.

“Missile warning is about bells ringing, missiles are coming, duck and cover, right?” Cruz said. “Missile tracking is about custody of a target. It’s about being able to look at that target and pass that information to a shooter that will engage it. And so there’s a nuance there. I think in our culture, as we’re moving forward [we’re having] the realization that we’re not just bell-ringers, that we’re actually contributing to a much broader engagement.”

When it comes to missile tracking, “the good news is that we have three different entities in government looking at this problem,” Stone told reporters in a June 6 briefing. “They’re looking at it, though, from a competitive vantage point, not an integrated development [vantage point].”

The Space Development Agency, scheduled to transfer to the Space Force later this year, has already spent years working on the National Defense Space Architecture, a massive constellation of hundreds of satellites in low Earth orbit for missile warning, communications, data coverage and sharing, and other uses.

The launch timeline for the Tracking Layer of the NDSA, which will handle missile warning and tracking, places it in orbit by 2025 or 2026.

The Space Force, meanwhile, is working on the Next-Generation Overhead Persistent Infrared System, the eventual replacement to SBIRS that will also fly in highly elliptical and geosynchronous Earth orbits. The service is also working on a network of satellites to go in medium Earth orbit.

Finally, the Missile Defense Agency is working on its own missile tracking system, the Hypersonic and Ballistic Tracking Space Sensor. Like the NDSA, the HBTSS would consist of satellites in low Earth orbit. The first two satellite prototypes are scheduled to launch in March 2023.

And while MDA director Vice Adm. Jon A. Hill has told lawmakers he wants HBTSS to integrate into the SDA’s Tracking Layer, Stone noted that “they initially were not designed that way” and remain as separate line items in the budget.

Rather than let those programs continue to develop separately, competing for funding, Stone’s study recommends combining elements from each to form an architecture with satellites in every orbit.

“Each of those organizations view their project as the answer, and that it’s resilient and cost-effective and everything and that everybody else’s is not, and that’s just part of the industry competition, no problem,” Stone said. “But I think it would be best if we took … a little bit of all these things, and we would have the capability, I believe, to achieve all those required attributes that’s lacking in today’s system.”

The advantages of such an approach are clear, said Davin Swanson, chief engineer in space and C2 systems for Raytheon Intelligence & Space.

“There’s the resiliency aspect, mainly through orbital diversity of the multi-layered approach,” Swanson said. “Having a multi-layered approach allows you to tune the sensor designs of each layer according to the optimal portion of that missile warning, missile tracking requirement set, depending on the orbit that that sensor is in. And it requires and it allows a shift away from the current paradigm of a small number of exquisite high-value assets to a more proliferated architecture where you’ve got more vehicles, different orbits.”

With the wider coverage of higher orbits and the higher fidelity of lower ones, such a system would ensure persistent missile warning and tracking, Stone and Swanson said. And it would also address the need for resiliency, an attribute emphasized by Space Force leaders, especially as countries such as China and Russia have demonstrated kinetic and non-kinetic threats.

“Just having hundreds of targets at LEO is not sufficient with an adversary who’s building a deep magazine of kinetic weapons and a multi-layered attack architecture across the spectrum,” Stone said. “We need to be able to plan for a survivable construct that can live through that sort of thing. And so instead of just having everything in one orbit, with everybody’s targets there to be hit, it’s best to have multiple layers and have a defense in depth approach.”

Stone also argued that if satellites in different orbits are integrated and work together, it will reduce the number of satellites needed overall—the Tracking Layer is currently slated to start with 28 and expand, and the planned MEO constellation could have 36 or more.

“If you want to do it the way that I recommended, you … don’t have to have the hundreds of satellites at LEO, the 36-plus at MEO, and five at GEO. You’ll need the five at GEO to have the global coverage, but as you go lower, as you integrate them all into one system, just three different orbits, you’ll need less satellites,” Stone said.

However, Stone also pushed for those satellites to be equipped with more advanced technology to increase their survivability against anti-satellite weapons. Such technology could include new propulsion methods and systems, or perhaps decoy satellites, he said.

Such additions, though, would drive up cost—an issue that retired Gen. Kevin P. Chilton, Explorer Chair of the Mitchell Institute, predicted would be the biggest hurdle to implementing Stone’s recommendations.

“I don’t think technology will be the pacing factor. I think the technology is there, and I think we will continue to improve it, and with this architecture, we’ll be able to update it more easily with reduced launch costs,” Chilton said. “Funding is always going to be cussed and discussed at [top levels of government]. … It’s a risk trade-off about how much you’re going to put up and how you’re going to do it. And so I think that’s where the big debates will be. But at the end of the day, there won’t be a debate on the need for these capabilities, in my view.”