Ka-band satellite constellation to benefit military forces

A new constellation of broadband commercial satellites is on track to provide remote users with faster communication speeds. The spacecraft will help meet the military's voracious need for communications bandwidth to support its far-flung global operations.

The first of the new satellites is scheduled to launch in September 2013, followed by another launch every six months until the entire constellation is in place. The service is planned to begin operating globally in 2014, Andrew Sukawaty, CEO of Inmarsat, said April 13 at the National Space Symposium in Colorado Springs., Colo. The three Boeing-built Inmarsat-5 satellites will have 89 Ka-band fixed spot beams and operate in geosynchronous orbit to provide flexible global coverage.

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Inmarsat chose the Ka band because it has twice the bandwidth of Ku band, Sukawaty explained. The spacecraft will be able to deliver 50 megabits/sec on the downlink to 60-centimeter dishes and 10 megabits/sec downlink to 20-centimeter dishes to while uplink speeds from the terminals will average five megabits/sec. This improved capability will provide a higher throughput to smaller, more portable terminals being deployed by civilians and warfighters.

The company will also offer ship and airborne versions of the terminal to meet growing demand for uplinks from platforms such as unmanned aerial vehicles. Sukawaty noted that the Inmarsat system’s service, called Global Xpress, will offer customers substantial cost savings with increased throughput. “There isn’t anything that you can do in Ku band that you can’t do with Ka band with more power,” he said.

One of the challenges faced by Ka-band systems was their susceptibility to rain fade—loss of uplink or downlink capability in bad weather. Inmarsat claims to have overcome this by increasing the system’s power and using adaptive coding techniques that slow down data streams to avoid losing information. The new system’s performance is comparable to Ku band, Sukawaty said.

Military satellites communications use has traditionally gone up for the company when forces are on the move. “We tend to get used when you have troop movement, not when everyone’s sitting on a base,” Sukawaty said. Inmarsat’s experienced a spike in satellite use during the first five months of U.S. operations in Iraq. There is also a jump in satellite communications use when troops withdraw, he said. The Afghanistan theater has also seen steady satellite communications use. This is because expeditionary and low-level warfare increase military connectivity needs, he said.

Commercial firms provide 80 percent of the satellite communications services to U.S. forces in Iraq. As military budgets shrink, this arrangement can be cost effective, he said. Sukawaty added that Inmarsat operates on a pay-as-you-go model similar to a commercial cell-phone contract. This is attractive to the military because there are no major capital investments involved with leasing commercial services.