Wideband satellites transform battlefield communications
Military and commercial satellites to provide broader coverage and address bandwidth surge
- By Barry Rosenberg
- Sep 09, 2010
Military leaders frequently say the next generation of a hardware system will be two, three or ten times better than the previous one.
So it's not surprising to hear Air Force officials say each Wideband Global SATCOM satellite will have 10 times the bandwidth capacity of the Defense Satellite Communications System satellites that they are replacing. Now that three WGS satellites are operational — with the third recently coming online in late June — what can the military do with that capacity that couldn’t be done before?
“Each WGS satellite can put out approximately 4.75 GHz of bandwidth, equating to 2.1 to 2.5 gigabits/sec of communications, which is quite extensive,” said Col. Donald Robbins, commander of the Military Satellite Communications Systems Wing's Wideband Satellite Communications Group at Los Angeles Air Force Base, Calif. Robbins is responsible for the WGS and DSCS programs.
“It gives battlefield commanders more capability to communicate across their entire area of responsibility,” he said, comparing the capability to live, satellite-transmitted TV from providers such as DirecTV. “It lets battlefield commanders work directly with ISR teams; it allows the fast-flyer aircraft to talk to the ground commanders. They can be more flexible in their [area of responsibility] because they have the ability to steer beams and allow higher volumes of data to flow through faster. Folks aren’t sitting on the other end of the battlefield waiting for information to download or waiting in a queue for channels to open up."
That increased capacity has facilitated new functions, Robbins said, citing a feature on each satellite that lets ground forces who are using an X-band terminal or radio communicate with other forces who are using a Ka-band terminal or radio. In the past, an X-band radio could only communicate with another X-band radio.
With radios that can operate across different frequencies, warfighters can receive communications and situational awareness at the same time. The X band is an older frequency, and there are thousands of X-band devices in various theaters of operation. For example, the DSCS satellites transmit over the X band.
However, communications over the Ka band are increasing because it has faster data rates and a higher capacity. For example, transmitters on unmanned aerial vehicles are transitioning to the Ka band to better handle live and high-definition video streams.
By supporting both the X band and Ka band, the WGS satellites help maximize Defense Department resources. Deployed forces that are already using one type of device don't need to carry another.
“All military services have procured radios and terminals over the years, and we want to make sure we connect the older radios with the newer radios,” Robbins said. “We don’t want to drive expensive changes across the military, so we were conscientious about not doing something with the satellite that drove the radio people to have to buy new terminals."
“In the long run, it is those terminals and radios that over time turn out to be more expensive than building the satellite itself because of the training and support that occurs over their life cycle,” he said. “The satellite has all its expense upfront, but the long tail of the cost is in the terminals, so we want the satellite to be as terminal-friendly as possible and not drive a lot of changes.”
Shape of Things to Come
The three operational WGS satellites support all combatant commands, with WGS 1 and 2 at 35 percent and 54 percent capacity, respectively, and operating an even split of X-band and Ka-band use, Robbins said.
“WGS 3 is being loaded as we speak, and users are being brought off the DSCS system and onto the WGS system,” he said. “All three of those satellites are getting more and more users as the terminals come in and out of theater. The utility of the satellites changes, of course, depending on the operations in that particular theater and how many terminals are moving in and out.”
Each of the first three WGS satellites is equipped with 10 Ka-band antennas. Eight of them provide narrow coverage, and the other two are area coverage antennas that are smaller than the others but cover a wider area. The coverage of the oval-shaped beam coming from the Ka-band antennas spans 600 miles, and the beam can be steered through a gimbal system.
“The ability to move that beam on the ground was not with the previous satellites,” said Mark Spiwak, Boeing's program director for WGS. “If you have a conflict in a certain area of the globe, you can gimbal the antenna and move that 600-mile footprint to wherever you want to put it.”
Each WGS satellite also includes two X-band phased array faces: one to transmit communications and one to receive them. They consist of eight X-band beams and one X-band Earth coverage beam. Like the Ka-band antenna, the X-band phased arrays are also steerable. They also can change shape to more effectively cover terrain.
“Let’s say I have comms around the coast of New Jersey,” Robbins said. “If I put a circular beam down in Asbury Park, half of my beam might be in the Atlantic Ocean, even though I don’t have any people in the Atlantic. Instead, I can shape the beam so it follows the New Jersey coastline.”
Because the beams from the phased array faces can be shaped, the satellite has the ability to tailor its beam around a signals jammer on the ground. “You’re able to communicate in the presence of a jammer and not be negatively impacted by a jammer on the ground,” Spiwak said. “We’ve been told that capability has been used.”
WGS Road Map
For now, the WGS satellites will coexist with the eight DSCS satellites that are in orbit until their fuel runs out. “The DSCS satellites still have utility until we bring the full fleet of wideband satellites into operation,” Robbins said.
Boeing is building WGS satellites 4, 5 and 6 at its Satellite Development Center in El Segundo, Calif. Those satellites, known as Block II satellites, will differ from the first three WGS satellites in two important ways.
First, to better align with the airborne ISR mission, the Block II satellites will do away with the two area coverage Ka-band antennas in favor of two more narrow coverage antennas. “The reason is to be friendlier to programs like Global Hawk to allow them more bandwidth,” Robbins said.
The second major modification relates to a bypass of the digital channelizer, which allows X-band radios to communicate with Ka-band radios, to increase bandwidth when using a Ka-band connection with a UAV.
“You can bypass it and have two dedicated channels through which you can have live streaming video directly from the UAV without having to go through the channelizer, which may limit the amount of bandwidth,” Spiwak said. “It gives you a really big pipe that allows direct streaming video from the UAVs and quite a bit of bandwidth in real time with high definition.”
WGS 4 is scheduled for completion in summer 2011 but probably won’t launch until 2012 because it must wait for a slot on a launch vehicle. WGS 5 and 6 are planned for launch in 2013. Their orbital locations have not been determined.
In late August, the Air Force awarded Boeing a contract to build WGS 7, with a launch scheduled for 2015. The service is in negotiations to procure satellites 8 through 12.
The WGS 7-12 Block II Follow On satellites would be clones of those in construction for Block II, though there are a variety of studies under way to add more capacity to those satellites to compensate for the canceled Transformational Communications Satellite program. The TSAT program was scheduled to play an important role in Warfighter Information Network-Tactical Increment 4 and other programs.
“Folks are discussing greater bandwidth and larger pipelines,” Robbins said. “Instead of 4.75 GHz, they’re talking about 10 to 20 GHz; instead of 2.1 gigabits/sec, they’re talking 10, 20, 30 gigabits/sec.”
Happy to Host You
Although the military is adding significantly more bandwidth through the WGS program, it anticipates that it will still need surge capacity for future conflicts. For that, the military turns to private-sector satellites, such as satellites that Inmarsat and Intelsat own. Those companies have started programs to build new commercial satellites that will include hosted payloads that the military can lease.
In August, Inmarsat contracted with Boeing to build three Ka-band satellites with 89 total Ka-band antennas. The Inmarsat-5 satellites support the same waveforms and terminals that the WGS satellites do, and the I-5 satellites also will include the hosted payloads.
The I-5 satellites are different because, for the first time, Boeing has also entered into a distribution partnership with Inmarsat to provide L- and Ka-band capacity to U.S. government users. Using their own resources, Inmarsat and Boeing will develop and jointly own the hosted payload, with the expectation that organizations such as the Defense Information Systems Agency will want to lease the payload at some point.
“It is unprecedented that a contractor like Boeing is partnering with a commercial operator to lease these services to the government, with a capability that works in concert with the core WGS system that is the backbone of wideband comms for the government,” Spiwak said. “It is unique in the industry, I believe, and is groundbreaking in how that was set up.”
Inmarsat characterizes the hosted payloads as a complementary service as opposed to capacity for a surge need. The company labels the service as complementary partially because of the expected bandwidth shortfall that will result from TSAT's cancellation. The potential need for more capacity in the aftermath of TSAT's demise also provides some of the rationale behind the WGS 7-12 Block II Follow On program.
“Comms-on-the-move for land, mobile users and ISR for unmanned aerial systems were big drivers for TSAT,” said J.J. Shaw, director of North America and global naval programs at Inmarsat. “The requirements are being recategorized with the cancellation of TSAT, but they are still there. What we’re looking to do at Inmarsat is to help supply some of the bandwidth and capability to support those major requirements."
“We’re taking some risk at Inmarsat [by developing a hosted payload that has yet to be leased], but based on our studies of the DOD and their requirements, we estimate that there is still a great need for that capability. Under our contract with Boeing, we look to them for their experience working with the DOD on these capabilities.”
Intelsat also has contracted with Boeing to build four communications satellites under a 2009 agreement, and two of those four satellites will include an ultra-high-frequency hosted payload. The first hosted payload, planned for the IS-22 satellite, was leased by the Australian Defence Force, and that launch is planned for 2012.
The second hosted payload was announced in late August, and it will be installed on the IS-27 satellite. The payload will offer 20 25 KHz UHF channels that can serve the U.S. government and other Intelsat clients. The second payload will be identical to the UHF payload designed for the Australian Defence Force. The company has not announced a customer for that payload.
ViaSat is another company looking to provide bandwidth for the military, though it seeks to provide that capacity in a different way. Rather than using a satellite built for broadcast, ViaSat plans to launch a satellite, named ViaSat-1, in 2011 that is specifically designed for two-way communications. Instead of having a capacity of 2.5 gigabits/sec, as WGS satellites have, it will support communications as fast as 140 gigabits/sec, said Ric VanderMeulen, vice president of government satellite communications at ViaSat.
“If Henry Ford had asked his customers what they wanted, they would have said ‘a faster horse,’ ” he said. “In our industry, we’ve been building faster horses because the satellite structure has been the same.… How do you make a better modem? How do you do better networking? How do you better compression? How do you make the antenna lighter? Everyone has been concentrating on sustained innovation. With these new satellites, we have a disruptive innovation that provides a new set of value propositions for two-way customers.”
By focusing on less area coverage and more spot beam coverage, ground terminals associated with ViaSat-1 can be smaller and provide more volume, while the space segment can operate at an overall lower cost, VanderMeulen said.
“The military has a great deal of interest in more capacity, and they are in the process of evaluating new technologies like this,” he said. “The point is that this is a new class of satellites that behaves differently.”
Space Systems Loral is building the satellite, which is intended to provide broadband to customers in North America.