LONDON — The agency providing U.S. government access to Iridium’s global constellation of mobile communications satellites on Nov. 9  urged other nations to join the program to take advantage of its fixed-price, unlimited-access feature.

Clare Grason, who manages the Enhanced Mobile Satellite Services (EMSS) program at the U.S. Defense Information Systems Agency, said allied nations are welcome to join the other “Five Eyes” nations — Australia, Britain, Canada and New Zealand — which have already joined the program as EMSS Fair Share members in addition to the United States.

“They have the same privileges as the U.S. Department of Defense,” Grason said at the Global Milsatcom conference here, organized by SMi Group.

“By that I mean they have unlimited access to the Iridium constellation through our gateway. Like Department of Defense agencies, they pay us a fixed rate. In return, they can add as many devices as they want to the network, provisioned by us.”

DISA, which is Iridium Communications’ biggest customer, is midway through a five-year, $400 million contract providing unlimited access to Iridium for U.S. government agencies that in turn pay DISA for the service.

Under the contract, all U.S. government communications are routed through the government-operated Iridium gateway in Hawaii. None of the traffic is routed through Iridium’s commercial gateway in Arizona or to the recently inaugurated gateway in Russia.

The Iridium constellation uses radio links to permit communications to be routed from satellite to satellite before landing at their destination without the need to touch down anywhere else.

The U.S. government, for security reasons, insisted on its own gateway. “Iridium has no insight into our usage trends, who are users are or where they are located,” she said.

Grason said 85,000 Iridium subscriber units have been activated under the contract, most for military users but about 15 percent for non-military U.S. government agencies.

The contract includes foreign nations’ access to Iridium insofar as these users are approved by DISA after clearing U.S. Foreign Military Sales approval.

“We charge our customers the same way Iridium charges us, on a fixed-prices basis,” Grason said. “Rates do not change no matter what the volume, so obviously maximum participation is encouraged.”

Government hardware not identical to commercial hardware

DISA has created firewalls that mean a government purchasing a commercial Iridium phone cannot simply apply the hardware to the DISA contract. For example, Iridium’s commercial push-to-talk feature, also called netted Iridium, is not usable on the DISA network.

Instead, government agencies seeking this feature must purchase equipment that can access the military version, called the Distributed Tactical Communications System.

The current range of this secure push-to-talk feature is about 160 kilometers, and up to 400 kilometers in certain cases. Grason said an upgrade is under way that will give this feature a global reach.

DISA customers must purchase secure Iridium handsets, which starting in mid-2017 will come with a new version of the Iridium Security Module and retail at about $4,000.

Equipment can be purchased directly through DISA or through a number of commercial Iridium value-added resellers.

DISA confident of signing new Iridium contract in 2018

Iridium’s current constellation is well beyond its planned retirement date. Launch of the second-generation constellation, called Iridium Next, has been delayed as launch provider SpaceX of Hawthorne, California, investigates the causes of an explosion of its Falcon 9 rocket in September while refueling in preparation for a test firing.

SpaceX and Iridium have said SpaceX could return to flight in December assuming the investigation wraps up by then with a clear explanation of the September failure.

Iridium has planned seven launches, each with 10 satellites, with SpaceX. Once the first batch is in orbit, the company will spending three months performing in-orbit checkout to validate system performance before proceeding with the second 10-satellite launch.

Subsequent launches could occur at 60-day intervals.

The DISA contract expires in October 2018. Grason said negotiations on a new contract, which she said DISA assumes will be signed and will stretch over five years or more, will begin in 2017.

DISA would not need to await until the second-generation constellation is in service to sign an successor contract, Grason said, as the agreement is for access to the constellation, not to a specific set of satellites.

The new contract is likely to include access to the higher-speed data rates available on the second generation of Iridium satellites, she said.

Peter B. de Selding was the Paris bureau chief for SpaceNews.