LONDON — A U.S. Defense Department MUOS satellite in geostationary orbit has successfully maintained telephone links with an aircraft flying over the North Pole — 89.5 degrees north latitude — in a demonstration that can only whet the appetite of U.S. allies, which for now do not have access to the relevant MUOS capacity.

Whether and when access to MUOS — the Mobile User Objective System — will be extended to U.S. allies was debated here Nov. 6-7 during the Global Milsatcom conference organized by SMi Group.

Two MUOS satellites are in orbit over the equator, and a third is scheduled for launch in 2014. Two more copies, including one to be used as an in-orbit spare, are in production at Lockheed Martin Space Systems.

In a presentation here, Justin Keller, director of advanced programs in Lockheed Martin’s military space systems office, said a C-130 transport aircraft fitted with an omnidirectional blade antenna maintained calls via MUOS while flying to 89.5 degrees north. The same performance could be expected in the Antarctic, he said.

Keller said MUOS’s design specifications call for the system to be able to maintain stable 24/7 call connectivity up to 65 degrees north latitude. But MUOS’s key advantage over the legacy UHF satellite communications systems that it is succeeding is its Wideband Code Division Multiple Access (WCDMA) payload.

The 16 WCDMA beams are designed to offer much faster tactical communications links, up to 384 kilobits per second.

Keller said the C-130 was flying at a speed of 300 knots at an altitude of 7 kilometers. An equivalent link between MUOS and a user standing at sea level would have been 83 degrees north, he said. He cautioned that stable communications at this latitude would not be assured on a 24/7 basis, but that the demonstration showed that some operations were possible much farther north than expected.

Global warming has made the Northwest Passage much more popular as a commercial sea route, and the widening ice-free areas make the region much more valuable, and potentially contested, for its energy and mineral deposits. Russia, Canada and Norway are all planning space systems to survey the Arctic region.

In addition to its 16-beam WCDMA capacity, delivered through a 14-meter-diameter unfurlable mesh antenna built by Harris Corp. of Melbourne, Fla., MUOS carries a legacy UHF payload designed to work with UHF radios already on the market and used by several allied nations to assure communications links for their troops.

Keller said the same flights that established the links with the MUOS WCDMA payload could not complete calls using the legacy UHF payload on MUOS despite efforts using this payload’s 5- and 25-kilohertz channels.

Several allied nations have purchased F-35 Joint Strike Fighter aircraft that, in principle, are designed with communications links to MUOS’s WCDMA payload. But the nations making these purchases are not receiving the communications pods with WCDMA because that payload is reserved for U.S. use only.

At least for now. Harold Haney, chief of space and missile defense in the Command, Control, Communications and Computers Division of the U.S. Strategic Command in Omaha, Neb., said the idea of opening all of MUOS’s capability to allies is a regular subject of debate.

“This could change. But until there are some political requirements for cooperation [with allies] on MUOS, we cannot change the policy,” Haney told the conference. “The F-35s that were sold to a number of nations were not sold with the MUOS boxes in it. The buyers will decide on the comms options themselves.”

Haney said at least part of the MUOS system would need a design modification in the event other nations became part of it.

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