The entire Defense Department is conducting “vibrant” discussions around what will be needed to develop the U.S. military’s next-generation missile warning and missile tracking architecture, with more details expected to be fleshed out as the next budget planning cycle begins.

The Space Force’s program to develop Block 0 of the Next-Generation Overhead Persistent Infrared (OPIR) early warning satellite constellation is well underway, and multiple interagency leaders are frequently meeting to discuss what comes next, three officials said this week.

The Block 0 program was launched by the Air Force in 2018 to build new missile-warning satellites in Geostationary Orbit (GEO). It is now managed by the new U.S. Space Force, with Lockheed Martin [LMT] and Northrop Grumman [NOC] serving as prime contractors. Critical Design Review is expected to occur in November 2021, and service officials requested $2.3 billion in research-and-development funding in the fiscal year 2021 presidential budget request.

Meanwhile, stakeholders across the Defense Department, including in the Space Force, Missile Defense Agency (MDA) and Space Development Agency (SDA), are working together to form a plan for Block 1 that will inform the FY ’22 Program Objective Memorandum, or POM, budgeting tool.

“Without getting in front of the budget process, I will tell you that the ’22 POM, we are looking very, very hard at the kinds of changes we believe we need to make into … the Block 1 capability,” said Shawn Barnes, who is performing the duties of the Assistant Secretary of the Air Force for Space Acquisition and Integration, during a June 16 webinar hosted by the Mitchell Institute.

Barnes noted that Block 1 should be different from what is being developed in Block 0 of the Next-Gen OPIR program. For that effort, Lockheed Martin is on contract to build three satellites for use in GEO with launches beginning in 2025, while Northrop Grumman will build two satellites for polar orbit to launch by 2029.

“We can’t continue to build a relatively precious few satellites that are in Geosynchronous Orbit, where they’re frankly, somewhat sitting ducks,” he said. While the Space Force is planning to incorporate new survivability technologies into the Block 0 systems to increase resiliency, more is needed, Barnes said.

“We’re looking far enough out that I think we need to be able to take a different approach, and that’s why the work that SDA and MDA are doing is going to be so important,” he added.

A main consideration for the department is how to incorporate a new proliferated constellation in Low-Earth Orbit (LEO), which is being fielded by the nascent Space Development Agency, into the larger missile warning architecture.

SDA Director Derek Tournear said during a Thursday webinar that an interagency working group is in the middle of studying what the next phase of early missile warning should look like.

“There is an interagency working group right now that is made up of the U.S. Space Force, MDA and Space Development Agency, and we are working together to come up with what the overall architecture beyond Block O should be for the department,” he said during a webinar hosted by the Small Sat Alliance.

He noted that there are different viewpoints about whether the department should immediately focus on a proliferated LEO network and then add more capabilities in Medium-Earth Orbit (MEO) and GEO later on, or to launch a hybrid architecture immediately.

“There’s pros and cons to both,” he said. “Obviously, the first way, where you rapidly proliferate LEO, gives you the fastest capability for conflict, just because the technology is the most mature. And it’s faster and easier to proliferate in LEO than in other orbits.”

However, focusing immediately on a hybrid architecture across orbits may lead to a more resilient network overall, even if it takes longer to field, Tournear noted. The working group plans to have an initial report on its findings this summer, he added.

As the Space Force works with Lockheed Martin and Northrop Grumman on the Next-Gen OPIR program, it also plans to launch the final two satellites in its current missile warning constellation over the next few years. Space and Missile Systems Center (SMC) Commander Lt. Gen. John “JT” Thompson said in a Wednesday webinar with the Mitchell Institute that the current Space-Based Infrared Systems (SBIRS) satellites on orbit are “exceeding expectations.”

The SBIRS systems, built by Lockheed Martin, are “enabling SMC … to balance the right speed, appropriate amount of innovation and risk posture to ensure that survivable missile warning into the ‘20s and then on into the ‘30s is out there,” he added.

The discussion has “really been vibrant, if you will, about what Block 1 needs to look like,” Thompson noted. “It really has been a whole of Department of Defense discussion regarding how these critical NC3 assets will look beyond Block 0.” NC3 stands for nuclear command, control and communications.

Thompson added that, for now, “all orbital regimes are on the table, and I really like the discussion that we’re having.”