In his remarks to the 2018 Space and Missile Defense Symposium in Huntsville, Ala., Lt. Gen. Sam Greaves, the head of the Missile Defense Agency, lays out his proposed space-sensor layer and describe what it could do.

HUNTSVILLE, Ala. — Missile defense leaders within the Pentagon and Congress are pushing for more missile defense capability in space, and the Missile Defense Agency director, Gen. Samuel Greaves, has a rough idea of what a space-based missile defense sensor layer could look like.

The missile defense community has been talking “seriously” about a sensor layer in space “actively over the last year,” Greaves said in an Aug. 8 speech at the Space and Missile Defense Symposium.

While many decisions still have to be made regarding requirements definitions, development paths and the acquisition process, “the key thing,” Greaves said, “is that there is serious consideration and support being given to the need to deploy these space sensors because we must do so.”

Greaves laid out a very rough sketch of what the agency is looking for to build a robust sensor layer.

First, the MDA might use something like a current system from the U.S. Air Force — the Overhead Persistent Infrared Global Scanning system — to alert and characterize activity in space, essentially “to be the bell ringer if something is going on,” Greaves said.

The sensor layer would have a regional detection and tracking capability staring down at Earth that could go after hypersonic threat detection and other “dimmer” targets, but also catch missiles in the boost or burnout phases of flight, Greaves described.

Covering the midcourse portion of a missile threat’s flight would be a sensor that could look “against the cold background of space” and discriminate, track and eventually serve as fire control, directly handing over data to ballistic missile defense weapon systems, he said.

At the far end of a missile trajectory, a sensor would stand by to record whether an intercept against a target was successfully destroyed or disabled, or whether it missed.

“Getting that capability into the architecture and providing that information to folks on the ground that have to make a decision on whether or not to re-shoot or whether to move onto another target, that is extremely important,” Greaves said.

The four-star added that the agency plans to also look at how the Defense Advanced Research Projects Agency’s Blackjack program might contribute to what the MDA is considering for a space-based sensor layer.

According to a DARPA broad agency announcement published in May 2018, the program seeks to develop and demonstrate “critical technical elements for building a global high-speed network backbone in low earth orbit (LEO) that enables highly networked, resilient, and persistent DoD payloads that provide infinite over-the-horizon sensing, signals and communications and hold the ground, surface, and air domains in global constant custody.”

Greaves said the agency and the Pentagon are now going through “intense discussion" on where it wants to end up with the architecture, pending department and congressional approval.

“Whether it’s the classic ballistic target into space and back down, or the hypersonic threat skimming at very low altitudes,” he said, “space offers, with the ground capability that we’ve got, the best integrated architecture to ensure we maintain both. It’s not more complicated than that, but if you don’t have it, you can’t see it shoot, and the remains of your system is essentially useless.”

Michael Griffin, the undersecretary of defense for research and engineering, told reporters at the symposium to expect to see changes in the space architecture as it is deployed in the future.

Echoing U.S. Strategic Command chief Gen. John Hyten, Griffin said the current space architecture is centered around "exquisitely capable, very expensive, very vulnerable systems that were designed and deployed in an era where we really didn’t have any space adversaries.”

Now adversaries, China and Russia are directly challenging U.S. assets in space “because they are critical to our way of fighting war,” Griffin added.

“As you look forward you will see changes in our deployed architecture to meet those challenges,” he said, such as a “proliferated space-sensor layer, for example,” that will not be made up of a few very large capable sensors, “but more less-capable sensors based off of commercial space developments.”