HUNTSVILLE, Ala. – The U.S. Missile Defense Agency is considering tracking ballistic missiles that could threaten the United States using a sensor in medium earth orbit.

In his most extensive public comments on space since 2012, Navy Vice Adm. James Syring, the head of the MDA, said the organization must have a space-based sensor layer as part of its long-term plans.

Since the Defense Department cancelled the Precision Tracking Space System, a constellation of missile tracking satellites, in 2013, MDA has faced questions about how the agency will take advantage of space.

“From a missile defense perspective, we have to develop a future operational space layer,” Syring said. “Given where the threat is going with hypersonics and more ICBMs and so forth this persistent tracking and discrimination capability from space is a must.”

The MDA has is currently studying what sensors it will need in the future as part of an analysis of alternatives. The analysis includes land, sea, airborne and space-based sensors, but ultimately could provide a framework for a future missile-tracking capability in space.

One of the options, Syring said, is what he described as a “MDA Space Concept Collaboration” that would call for a missile-tracking sensor in medium earth orbit. It is not clear is the senor would operate as a payload or on a Defense Department satellite.

MDA officials have said it is unlikely they would launch agency-only satellites and that instead, any sensor likely would be part of a broader Defense Department effort.

But Syring said PTSS and other space-based experiments from the past 15 years have proven there is value to space-based sensors.

While the Pentagon cancelled PTSS, “that doesn’t mean our will and commitment has stopped. The bottom line remains, we need this tracking capability,” he said.

In the meantime, the agency is depending on its Spacebased Kill Assessment program to help the MDA decide how to best use space.

SKA is an experimental network of space-based sensors that would launch aboard commercial satellites beginning next year. The sensors would verify whether incoming missiles have been destroyed by defensive interceptors and no longer pose a threat. The first payloads will view intercept tests over the Pacific Ocean, Syring said.

“Is it precision tracking worldwide? No. But it will allow us now to see and test this capability,” he said. “It’s vitally important, understated but understood step on where we’re going in space. The foundation of that thinking is critical. Space does not have to be expensive. I think we’re in groupthink in these satellite programs need to cost tens of billions of dollars.”

According to MDA budget documents, the first payload would not launch before spring 2017, with the second and third launches slated for sometime later that summer. MDA has not identified any of the host satellites, although several industry sources say the likeliest candidate is the Iridium Next constellation of mobile communications satellites.

Mike Gruss covers military space issues, including the U.S. Air Force and Missile Defense Agency, for SpaceNews. He is a graduate of Miami University in Oxford, Ohio.