A SpaceNews artist's concept depicting an Iridium Next mobile communications satellite observing a missile defense intercept.

WASHINGTON — The U.S. Missile Defense Agency has been careful not to identify the satellites that would host its planned network of experimental kill assessment sensors, but industry sources say the likeliest candidate is the Iridium Next constellation of mobile communications satellites.

To be clear, the MDA has not even confirmed that the host satellites would be commercial, and in fact there are publicly disclosed examples of military payloads operating aboard classified satellites. But industry sources say the MDA’s host satellites are indeed privately owned, and the agency itself has said the Spacebased Kill Assessment program is modeled after the Air Force’s successful Commercially Hosted Infrared Payload experiment, which featured a missile warning sensor hosted aboard a commercial telecommunications satellite.

It is no secret that Iridium Communications, McLean, Virginia, has been looking for more payloads to host aboard its next-generation constellation. But the company, while hinting that it has had some success of late, will not talk about the MDA project. Nor will Harris Corp. of Melbourne, Florida, which is under contract to seek out and arrange hosted payload missions aboard the Iridium Next satellites.

The Spacebased Kill Assessment sensors would verify whether incoming missiles have been destroyed by defensive interceptors and thus no longer pose a threat. The program, first disclosed in the MDA’s budget request for fiscal year 2016, appears to represent the agency’s first known foray into commercially hosted payloads, whereby typically government organizations fly dedicated instruments aboard commercial satellites.

Most commercial satellites operate in geostationary orbit at 36,000 kilometers, whereas the 72 satellite Iridium Next constellation will operate in low Earth orbit.  The MDA has not specified the orbit of the kill assessment sensors, but what it has said about the program in budget documents would appear to point to Iridium.

  • Multiple sensors planned, each of which will have to be integrated onto the host platform. Because the Iridium Next satellites are virtually identical, the nonrecurring cost of integrating the payloads would be minimized.
  • The Iridium Next satellites are built by Thales Alenia Space in Europe, but are undergoing final assembly and integration at the Gilbert, Arizona, facilities of Orbital ATK. That would mean the 10-kilogram kill assessment sensors, being managed the Johns Hopkins University’s Applied Physics Laboratory of Laurel, Maryland, do not have to be shipped overseas or handled by non-U.S. citizens — the MDA might find either objectionable.
  • In a similar vein, all but the first two the Iridium Next satellites are slated to launch aboard American-made rockets: Falcon 9s built by SpaceX of Hawthorne, California. A large percentage of commercial geostationary satellites are built and launched overseas — many aboard Russian operated rockets — a fact that could substantially narrow the field of suitable geostationary candidates to host MDA sensors.
  • The MDA says the Spacebased Kill Assessment sensors are slated to launch starting in the fourth quarter 2016 and continue in 2017, which parallels the Falcon 9 launch schedule for the Iridium Next constellation.
  • The MDA says the project will take advantage of an existing ground network. Although there are plenty of networks, commercial or otherwise, that are applicable, it is noteworthy that Iridium’s ground network includes a specially built gateway station to handle sensitive U.S. military communications traffic.

Rick Lehner, a spokesman for the MDA, said in an April 2 email he was not able to provide information about potential host spacecraft for the Spacebased Kill Assessment program. Diane Hockenberry, a spokeswoman for Iridium, declined to comment for this story, as did Sleighton Meyer, a spokesman for Harris.

Iridium has long viewed hosted payloads as a way to help defray costs of the $3 billion Iridium Next constellation, which is expected to become operational in 2017. To date, the only known taker is the Aireon venture, which was co-founded by Iridium and aims to sell precise flight navigation data to airline operators and aviation authorities.

The Aireon payloads, designed to relay Automatic Dependent Surveillance-Broadcast aircraft navigation signals, are supplied by Harris and integrated into the Iridium Next bus using Harris’ Appstar hosted payload accommodation module.

Iridium Chief Executive Matthew Desch in November said efforts to secure additional hosted payload customers for Iridium Next were going better than expected and would generate $55 million in revenue for the company, compared to previous estimates of $45 million.

The MDA is seeking $22 million next year for the Spacebased Kill Assessment experiment, which it expects to operate through 2020. But the agency has been quietly pursuing the program for at least a year using funding left over from a canceled missile tracking satellite program.

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.