Satellite Communications

Even before the successful launch of Sputnik by our Cold War nemesis, American military leaders saw the potential for spacebased communication.

As early as 1946, the Army experimented with bouncing radar signals off the moon. The Navy continued such experiments throughout the ‘50s and ‘60s with a clear understanding that the country that dominated space also ruled the battlefield. Today, satellite communications (SATCOM) are an essential force multiplier in aiding commanders to see through the “fog of war,” especially during special forces operations.

“Satellite communications are typically used when wireline or fiber infrastructure is not available, or when the range exceeds what can be provided by line-of-sight radios,” explained Scott Whatmough, vice president of integrated communication systems, Raytheon. “Satellite communication has the advantage of being usable anywhere there is an unobstructed view of the sky and an available satellite.”

The first military satellite communications network, the Defense Satellite Communication System (DSCS), went live in the late 1960s. Over the years much has changed, and been learned, about improving, remodeling and redesigning satellite technologiesfor the needs of DoD. Subsequent generations of SATCOM have been driven by the need to provide more secure and jam-resistant links to tactical users with smaller and more powerful, yet less power hungry terminals on the ground.

This meant satellites needed to have more powerful and more efficient solar cells, and eventually, new telemetry techniques and attitude control that allowed more time in proximity to permit more sustained capture of the sun’s energy. Such capabilities, along with ground control of satellite positioning and orientation, are now fundamental to all military satellites.

According to an official spokesperson with U.S. Strategic Command (STRATCOM), “Satellite communications play a vital role in warships, aircraft, missile guidance and several other critical programs that support multiple areas of responsibility. Traditionally our ‘transportable’ communication systems have had the capability of being deployed by mobile communication units to our larger forward operating bases. These types of deployments were typically used to support units of 50 to more than 100 warfighters, offering a complete suite of communications capabilities. In the past decade, deployment sizes have changed; so have traditional thinking and the needs of the warfighter on the ground.”

Today, what has really made SATCOM the dominating force multiplier it has become, especially in the SOF community, is the development and deployment of mobile and tactical military satellite communication systems. Such small and portable SATCOM systems typically are composed of ground terminals with very small antennas that can be mounted traditionally on ships, submarines and aircraft, and more recently on ground vehicles and lightweight man-pack terminals, which can transmit to tactical radio handsets that in some cases are not much larger than cell phones. These mobile systems primarily transmit voice and data, and in the latest generations even leverage video and other broadband real-time tactical applications.

“As the war in Iraq went into full swing, auto deploy antennas became very popular with the U.S. Army,” said David Provencher, general manager for Orlando, Fla.-based Cobham Antennas SATCOM Landsystems. “Comm-at-the-pause very small aperture terminal (VSAT) technology really took off and dominated the DoD market. The next evolution in controls technology was comm-onthe- move. There is comm-on-the-move all the way from UHF to Ka-band today. In 2007, we developed what we call a mid-profile comm-on-the-move antenna. The thing that is driving and dominating [the comm-on-the-move] market today is ISR on UAVS.”

According to STRATCOM’s spokesperson, “In the past few years, a decrease in the size of deployed units made the typical deployable command, control, communications, computers and ISR systems impractical. The communications systems designed to be transportable and support large units are now too large to meet the demands of today’s streamlined rapidly-deployable forces. The challenge today is how to scale back the footprint of these systems while still offering a robust capability for the deployed forces so that we have ‘satellite communications availability’ at the lowest level for our warfighters.”

Global Network, Global Power

In addition to STRATCOM, another entity largely responsible for developing, maintaining and operating the nation’s MILSATCOM network is the Space and Missile Systems Center MILSATCOM Directorate (SMC MILSATCOM) based out of Los Angeles Air Force Base in El Segundo, Calif. At present, the directorate encompasses a total force of approximately 102 assigned military, 148 assigned civilians, 184 federally funded research and development center contractors, and 378 other contractors. That combined group of experts and thought leaders is dedicated to meeting some of the challenges facing DoD when it comes to next-generation satellite communications. According to an SMC MILSATCOM spokesperson, “The greatest challenge facing the DoD with respect to satellite communications is meeting the growing demand for connectivity, capacity and protection in a more affordable manner in order to support the foundational level of space our nation relies upon. The MILSATCOM Systems Directorate has released a broad agency announcement to involve industry in addressing the development of future MILSATCOM architectures, to include better business practices to optimize capability and minimize costs.”

He added that “the recent airborne flight demonstration of a low-profile Advanced Multiband Communications Antenna System prototype at EHF/SHF frequency bands is an example of such technology risk reduction efforts. In addition, the directorate is investigating approaches to leverage commercial SATCOM capabilities and services.”

Satellite operators agree that an increased reliance on commercial satellites may be the way forward in meeting DoD’s growing appetite for SATCOM. “Future deployments that require beyond line-of-sight services will be relying more on commercial offerings that complement military SATCOM,” said Steff Taylor, director of government services for Inmarsat. “In an asymmetric warfare environment, the need for costly MilSpec satellites in orbit is not as critical. It is now possible that policymakers and operational planners will outsource more to COTS [commercial off-the-shelf], including fully managed services.”

Inmarsat operates a fleet of 11 satellites, and is responsible for creating the Broadband Global Area Network, which provides secure and reliable mobile voice and broadband data communications “on the move” or “at the pause” for ground forces worldwide. Based in the United Kingdom, Inmarsat is currently working with Boeing to manufacture, deploy and operate a new constellation of satellites, the Inmarsat-5s. That will form the backbone of a the future Inmarsat Global Xpress network, which will be capable of delivering mobile broadband at speeds of up to 50 megabits per second.

Space Links

The issue with comms-on-the-move, according to Cobham’s Provencher, is “there is a huge tradeoff that has to take place between the size of the antenna and bandwidth efficiency. SOF wants small antennas, and the network really needs to be designed around the size of the antennae. Most satellite networks are comfortable and are legal to operate at Ku-band, and to a certain extent Ka-band, at around a 1.2-meter antenna. Obviously, you can’t put a 1.2 meter antenna on a UAV. But, when you go smaller than that, the beam width of the antenna gets wider, and that can cause adjacent satellite interference.”

Traditionally SOF is not under the same budgetary constraints as are other branches of the military. Provencher was not at liberty to disclose which units of SOF are customers of Landsystem’s comm-on-the-move antennas, but he did say, “If you are not on a tight operating budget for bandwidth, then you can use small aperture antennas, you can run the modulation schemes that don’t violate all of the international regulations and rules. So SOF does have an advantage there. But also even if it is not comm-onthe- move, but comm-at-the-pause, SOF has the same issues even when they are not moving. When you stop and break out a dish from your rucksack, set it up, it’s still very small, and has the same constraints and challenges of a comm-on-the-move antenna.”

System integrators realize that issues of size, weight and power are always of greatest concern with any gear operated by the SOF community. “Raytheon is engaged in several activities related to developing and deploying terminals on smaller platforms,” explained Raytheon’s Whatmough. Raytheon is the supplier of the Secure Mobile Anti-Jam Reliable Terminal (SMART-T) to the Army and Air Force and international partners.

Whatmough continued, “We have constantly evolved the electronics in our terminals over the past three decades to make them smaller, less expensive and higher in performance. One of the key technologies for smaller terminals is lightweight, low profile, high performance antennas. Over the years we’ve invested in antenna technologies that are suitable for smaller platforms and for mobile platforms.”

Moving forward, surmounting these kinds of beyond line-of -sight challenges facing special forces will require an integrated approach of manufacturers, system aggregators and satellite operators, Taylor predicted. “In order to be in a position to meet [DoD’s] changing requirements, the launch of our new Ka-band service, Global Xpress, will complete the portfolio of services that range from very low data rate through to true broadband capability in a highly mobile platform,” he said. “The Inmarsat portfolio fits exactly the requirements of special operations for mobility, reliability and ease of operation. These services will be available to military customers and will complement existing MILSATCOM in the future.”

Looking Up

The aerospace industry, along with STRATCOM and SMC MILSATCOM, has helped to dramatically improve and expand military satellite communications capabilities over the past few decades. Systems have evolved from single channel to today’s high-capacity systems, leveraging greater power, wider bandwidth and improved waveforms for secure tactical communications, with an ever-expanding assortment of terminal types. That development of small lightweight terminals has likely had the largest impact on the SOF community. From an early infrastructure of only a few large fixed terminals, SOF field operatives can now rely on thousands of small mobile terminals.

With more than 50 years of experience in providing the full range of military satellite systems in support of DoD, the contractors and vendors of the U.S. aerospace industry are uniquely positioned to apply lessons learned in space to the needs of the warfighters on the ground.

“As I see it,” concluded Cobham’s Provencher, “the biggest hurdle for SOF moving forward will continue to be, how do we make it small enough for these types of operators to carry along and use it inconspicuously, but give them the bandwidth that they need to do radio communications as well as ISR data rate communications? That’s a trade-off and requires cooperation from everybody, from the satellite manufacturers and operators, to the antenna makers, to the end-user.”

As military satellite communications systems continue to evolve and give way to the next even more advanced generation, these companies and military thought leaders will continue to make major contributions in each phase of acquisition, development and deployment.

Πηγή