LONDON — The U.S. military’s Wideband Global Satcom (WGS) constellation of X- and Ka-band satellites will nearly double its per-satellite throughput with the last three spacecraft now under construction, a U.S. Air Force program manager said Nov. 28.

That will be good news for a system that, according to Air Force assessments, has not been able to produce the amount of bandwidth expected of it, at least for the first satellites in orbit.

In a Nov. 28 presentation here to the Global Milsatcom conference, organized by SMi Group, David Steare, lead for international milsatcom engagement at the Office of the Deputy Undersecretary of the Air Force for International Affairs, said the current WGS satellites each generate 2 to 3.5 gigabits per second of throughput.

That is less than the 3.6 gigabits per second that was the program’s baseline specification. But according to an Air Force Selected Acquisition Report published this year, the current estimate is that each satellite is delivering still less than that — around 2.1 gigabits per second of capacity.

The report also said WGS is not meeting its goal of providing coverage as far as 70 degrees north latitude; 65 degrees north is about the limit. The goal of reaching as far as 65 degrees south has been achieved, the report said.

Four WGS satellites are in operation in geostationary orbit. Aided by two international partnerships — one sealed in 2007 with Australia, the other concluded in January with contributions from Canada, Denmark, New Zealand, Luxembourg and the Netherlands — the Air Force has ordered six more spacecraft from manufacturer Boeing Space and Intelligence Systems of El Segundo, Calif.

Launches of these satellites are scheduled to occur between 2013 and 2018.

Steare said the five nations joining in January will benefit from a 25 percent reduction in the cost of their participation because the Air Force was able to negotiate a better price from Boeing for the ninth WGS spacecraft, whose construction these nations are financing.

The five nations combined had agreed to a ceiling cost of $619.7 million. This is the figure that has been reduced by 25 percent.

Under the agreements, each nation is allotted a fixed percentage share of the capacity of the entire WGS constellation based on its financial contribution. Australia’s share is 5.59 percent, Canada’s is 1.77 percent and the other four nations have less than 0.3 percent each.

WGS partner nations said here Nov. 27-29 that they assume the guarantees will hold even in a scenario in which several or all of them, and the United States, are members of a coalition waging a military action in an area where satellite communications is crucial.

The amount of Ka-band capacity to be made available to troops in operational theaters has been a subject of debate, especially since commercial satellite operators are building Ku- and Ka-band satellites with military customers in mind.

Commercial providers have said that even with 10 WGS satellites in orbit — Steare said the Air Force is open to building more if other international partners wish to join — there will not be sufficient throughput to support a military engagement.

Mobile satellite services provider Inmarsat of London is building a constellation of three Global Xpress Ka-band satellites that was designed from the start to complement WGS.

Peter Hadinger, president of Inmarsat Government Services, said Global Xpress capacity can fit in seamlessly to a military platform without forcing users to change hardware. The first Global Xpress satellite is scheduled for launch in the summer of 2013, with the two others to follow at six-month intervals.

A U.S. Defense Department official confirmed that Inmarsat has consulted with U.S. defense authorities from the start on Global Xpress, going so far as to position the Inmarsat spacecraft in orbit so as to maximize synergy with WGS. Global Xpress uses both the civil and military Ka-bands, which are next to each other on the radio frequency spectrum.

Commercial satellite fleet operator Intelsat of Luxembourg and Washington is building a new brand of high-throughput Ku- and C-band satellites, called Epic, that will deliver up to three times the bandwidth of WGS.

O3b Networks of Britain’s Channel Islands, which is backed by fleet operator SES of Luxembourg, plans to start launching its constellation of medium Earth orbit Ka-band satellites next year.

O3b Chief Executive Steve Collar told the conference here Nov. 28 that the O3b satellites, designed to cover the globe between 45 degrees north and 45 degrees south, can train 350 megabits per second to a given vessel or carrier group and then follow the ships, handing off from one satellite to another.

Peter B. de Selding was the Paris Bureau Chief for SpaceNews.