After years of attempts by the U.S. intelligence and defense space communities to jointly develop satellites to serve their diverse needs, an amicable divorce appears to be under way as the two communities explore future constellation architectures.

And they appear to be taking vastly different architectural approaches.

The Pentagon, which supplies satellite services for deployed forces, is exploring the concept of “disaggregation” or “passive resilience”— distributing its space-based capabilities across more platforms.

The National Reconnaissance Office, which develops and operates U.S. classified satellites, is taking a different approach. Though the NRO often deploys small experimental systems, the preponderance of its requirements will likely continue to be met with very large, highly capable and expensive satellites, says U.S. Air Force Maj. Gen. Susan Mashiko, deputy NRO director.

While Air Force Space Command and others are exploring new ways to provide long-standing services—including missile warning, communications and space situational awareness—there is a deliberate push not to lose sight of the need to execute today's programs in the near term.

These projects—the Space-Based Infrared System (Sbirs), Wideband Global Satcom, Advanced Extremely High Frequency system and others—came at high cost in the past 15 years of technical and management challenges. Officials are loath to squelch those investments by abruptly embracing a new architecture and plunging into new designs.

So the increased talk by senior Pentagon officials at last week's 27th National Space Symposium here about disaggregation is likely the beginning of a long process to deliberately reshape constellations. “The die is cast for the next 10-15 years just because of the development timelines, . . . but there is an opportunity right now to start to turn this ship,” says Gen. William Shelton, Air Force Space Command chief. “I am absolutely convinced there are better ways to do the mission we are charged with doing. . . . I'm more right now thinking of disaggregation, not aggregation.”

There has been sporadic interest in crafting a distributed satellite network, but there has also been little impetus to embrace it. Partly due to the high cost of launch, the Defense Department has continued to build small numbers of very large, sophisticated and expensive satellites. For the foreseeable future, the cost of launch will not change.

But two major factors are changing. Downward pressure on the federal budget may force the Pentagon to get creative and abandon the sophisticated designs of the past. Perhaps more compelling for defense officials is the sharp increase in the number of operators in space, making it more difficult and dangerous to operate there. The vulnerability of satellites, many costing well over $1 billion, to orbital debris, jamming or an antisatellite weapon has increased.

The disaggregation concept calls for a distributed architecture that can execute the majority of its mission even if one satellite is compromised. It can be achieved by fielding more satellites or more payloads hosted on non-defense platforms or devising alternate data paths.

In addition, to address the increased threat and reduced funding, Pentagon officials are exploring how to simplify satellite designs, which goes hand in hand with disaggregated architectures, defense officials say.

The Pentagon is buying hosted UHF communications payloads now, but that is due to urgent need, not a strategic bent toward producing a new architecture.

These two new approaches could play out more deliberately in the missile-warning and -tracking arena in the next decade. The Missile Defense Agency will pursue a simpler design for its next space-based missile-tracking system than the two Northrop Grumman Space Tracking and Surveillance System (STSS) satellites now conducting a demonstration in space.

MDA's choice was based on a recommendation from the Johns Hopkins University Applied Physics Laboratory (APL), which leads the study of design options for the follow-on Precision Tracking Space System (PTSS).

Two Northrop Grumman satellites are designed with both target acquisition and tracking sensors made by Raytheon. Together, the sensors were designed and have proven the ability to conduct “birth-to-death” tracking of ballistic missiles. “It is actually showing that the space layer can contribute birth-to-death tracking,” says Doug Young, vice president of missile defense and warning programs at Northrop. “It is causing folks to really rethink BMD possibilities.” During one exercise last month, the satellites proved “stereo tracking”—or passing off target tracking from one satellite to another.

While the STSS acquisition sensor is designed to detect a hot missile plume in the shortwave infrared (IR) bands, the tracking sensor is optimized to follow a cold warhead during its difficult-to-detect midcourse of flight using mid- and longwave detectors. This requires multiple onboard focal planes and telescopes.

For PTSS, however, MDA is opting to forgo target acquisition, and design a satellite for tracking only, to reduce the price and risk for development. This will drive MDA toward improved communications and networking for offboard cueing.

APL has issued six subcontracts—to Lockheed Martin, Boeing, Northrop Grumman, Raytheon, Ball Aerospace, and Orbital Sciences Corp.—for final design input, but an acquisition and manufacturing plan is not yet firm. APL will likely design and build the first two development satellites, and up to 10 more could be produced by industry. Though launch was originally planned for 2014, it is now expected in 2016.

Meanwhile, the Pentagon could eventually shift to a disaggregated architecture for the IR missile-warning mission beyond Sbirs. Prime contractor Lockheed Martin is slated to build four Sbirs geosynchronous birds and two more are expected to be purchased through a block buy approach. But senior defense officials argue there is still opportunity for a parallel disaggregation strategy without terminating Sbirs purchases.

Technology for wide-field-of-view focal plane arrays needed for a future missile-warning system is maturing. Raytheon is among the companies developing these arrays, partly because the Pentagon funded a parallel sensor path for fear Sbirs would crater. But, without some assurance that continued company funding will eventually come to fruition in a formal government program, Raytheon will have to consider leaving the market, says Tom McDonald, a director at Raytheon Space and Airborne Systems.

Raytheon is proposing a modular approach to future space-based missile-warning and -tracking. Building off of its Responder modular satellite concept, the company is proposing a missile-warning toolkit. The concept calls for common-use components—such as processors, cryocoolers and telescopes—mated with specialized focal plane arrays optimized for a particular mission, such as short-wave IR for missile warning and longwave IR for missile tracking.

Meanwhile, a select group of contractors could pair up for work, if the Lockheed Martin/Northrop Grumman team loses its grip on the early missile-warning mission now occupied by Sbirs. Northrop Grumman and Boeing executives have quietly signaled they would be interested in priming a future team, though Northrop now officially supports the Lockheed-led Sbirs program because its Asuza, Calif., facility builds the payload.

Other potential payload providers include Raytheon and Goodrich.