Satcom To Aircraft: Providing Communications To Smaller Jets

By | January 1, 2008 | Cover Story, Telecom

The insatiable hunger for bandwidth is not limited to the ground, as demand for connectivity now extends well into the stratosphere. A variety of end users are clamoring for more bandwidth, and the reason is simple: Increased connectivity while aloft multiplies the effectiveness of airborne applications. Stabilized platforms are commonplace on vessels and trains, and they are growing in popularity on smaller jets.

Making data fly is no longer just a speed consideration. Companies literally are making it fly by providing specialized communication systems that allow aviators and their passengers to communicate with anyone around the globe via satellite while in flight, and the market for providing satellite-based communications to aircraft continues to grow. The market for high-bandwidth satellite communications generally is aimed at larger private jets with transcontinental capabilities and military aircraft, while the market for lower bandwidth communications to all types of smaller aircraft is much broader and growing just as rapidly.

The Challenges Of Flight

The biggest engineering challenge for the market is keeping an aircraft-based antenna locked onto the proper satellite, which requires either a gimbaled parabolic antenna or steerable array mounted somewhere on the fuselage. Both types of antennas use positioners that keep them in the proper orientation. The positioner receives input from the inertial navigation system on the aircraft so it can track the satellite.

All military aircraft, including fighters, will be equipped with satellite terminals in the not too distant future. As you can imagine the needs of a combat aircraft and a business jet are significantly different. As a rule, most business executives are not fans of snap turns and barrel rolls; therefore, maintaining lock on the satellite is relatively easy for most civilian satellite communications systems. The exception would be a tight turn where the wing or fuselage momentarily interrupts line of sight to the satellite. Military aircraft, on the other hand, make cat-like turns and twists, requiring multiple antennas to maintain lock on a satellite. Antenna positioners must be lightning fast and be able to withstand tremendous strain.

Service Options

There are a handful of service providers that have carved out profitable niches in the aviation segment, with Iridium and Inmarsat the two standard bearers when it comes to providing low- and medium-speed satellite communications to aircraft.

Iridium operates a constellation of 66 low-Earth orbit satellites and is the only commercial satellite operator that provides truly global coverage, says Iridium President Matt Desch. The aviation market is the company’s smallest but fastest growing market segment. “The reason why we have been so successful in the aviation market is that we have very low latency and our hardware has very low power requirements, which means we can use very small antennas and small electronic packages. You don’t have to have these very large things in the tail of the aircraft that point towards the satellite. Therefore the overall costs of the system are lower,” he says. The nominal data rate of Iridium’s network is 2,400 bits per second — slow by broadband standards but entirely adequate for air traffic controls instructions and flight planning information.

Iridium teams with partners who specialize in the aviation market, such as Blue Sky Network. In addition to providing in-flight voice and data, Blue Sky Network provides a number of value-added services which are accessible through its SkyRouter Web portal. Asset tracking is one such service that is popular with clients, such as the U.S. Forestry Service, which requires a huge number of aircraft to detect and fight fires every year. Fire season begins early in the year in Florida, and as the weather warms, forest fires begin appearing in other states. Keeping track of 1,500 aircraft that constantly are being dispatched throughout the United States is a huge task. Blue Sky Network’s asset tracking service provides the Forestry Service instant updates on each of the contracted aircraft’s location, which eliminates the guessing game for firefighting strategists.

Inmarsat launched its SwiftBroadband service in the Atlantic and Indian Ocean regions in October. As the name implies, SwiftBroadband band is the aeronautical equivalent of Inmarsat’s Broadband Global Area Network service and provides data rates up to 492 kilobits per second (kbps) via Inmarsat’s two I-4 satellites. The channel is shared among multiple users and throughput will vary. Inmarsat traditionally has billed customers by the minute for service but is changing strides with SwiftBroadband, which uses a throughput-based billing system.

Stratos Global Corp., the largest provider of Inmarsat services around the globe, serves the aviation market directly and through distribution partners, and Bob Roe, president of Stratos Government Services, sees strong potential with SwiftBroadband. “The business and government aviation markets are growing,” he says. “Executives want to stay in touch and take their offices with them on a trip, requiring connectivity for voice, e-mail and video conferencing applications. With broadband connectivity, an executive can make a phone call while downloading a data file. They couldn’t do that in the past. The need for value-added services in the aviation market is growing at a fast clip.”

Stratos uses partners such as Satcom Direct to provide additional services through SwiftBroadband such as weather, fuel and business services, says Roe. Stratos also allows customers to manage their SwiftBroadband service through a Web portal. Since the service is traffic sensitive, the dashboard allows the client to monitor the usage in real time so there are not any surprises when the bill arrives.

SwiftBroadband will be rolled out in the Pacific region after the launch of their I-4 satellite, which is scheduled for the first quarter, and the development of SwiftBroadband has not sounded a death knell for Swift64, an earlier service delivered by Inmarsat. Swift64 allows streaming service, which is not yet available through SwiftBroadband. Aircraft owners can connect Swift Broadband and Swift64 terminals to existing antennas and use either service, or both, simultaneously.

At the upper end of the aviation communications market, Arinc’s SkyLink service uses Ku-band satellites and delivers the highest throughput of any commercially available satellite communications service to aircraft, with inbound speeds between 1 and 3.5 megabits per second and a return channel with speeds of 128 to 512 kbps.

The SkyLink service uses airborne satellite hardware and a ground infrastructure developed by ViaSat. The on-board terminal uses a 30-centimeter antenna, which is housed inside a radome and has a beam width of 6 degrees. To avoid splashing other satellites with interference, a spread spectrum technique is employed to lower the spectral power density, thereby lowering the interference effects below those of a traditional 1.2-meter antenna.
SkyLink is available over the continental United States, Western Europe, the Caribbean and the northern third of South America. The footprint also covers a large amount of ocean, including the Northern Atlantic between North America and Europe, the Gulf of Mexico and large portions of the Pacific.
Each of these services offer different advantages and disadvantages to users, and each is aimed at a specific audience. Iridium provides the smallest hardware package and the least amount of power, and its global availability makes it a good choice for trans-oceanic flight. Although the service is traffic sensitive it is a cost- effective means of delivering reliable weather and flight data to the cockpit.

SwiftBroadband also enjoys global coverage, but the hardware footprint, weight and power usage is greater than Iridium. The satellite channels are shared, much like a system that uses cable modems, and throughput can suffer during peak times. The service is traffic sensitive and end users will pay more for Voice Over IP and e-mail connectivity.

The SkyLink service provides much higher throughput but can only be installed on larger jets due to the size and power requirements of the on-board platform. The hardware cost is the highest of all but the recurring cost per bandwidth is the lowest on a per bit basis.

Military Initiatives

It is hard to imagine that just 20 years ago the majority of military aircraft relied solely on ultra high frequency and very high frequency frequencies to communicate, but improvements are being made rapidly due to the concept of netcentric warfare, which envisions every aircraft, vehicle and ship communicating through the same network. Satellite communications is central to this effort. Satellite-based communications to smaller military jets — including fighters — is the wave of the future, and generals and admirals — the military equivalent to titans of industry — and their VIP aircraft are the first to be being outfitted with terminals so commanders are in constant contact.

“Once data is sent to a satellite, it can be relayed anywhere,” says David Smith, vice president and general manager of EMS Technologies’ Defense & Space Systems division. “When satcom terminals are installed on aircraft and live video can be uplinked, the Pentagon can see exactly what the pilot sees. This will have a tremendous impact. For instance, command officers can make a call if there is a question about the rules of engagement,” he says.
The Pentagon’s larger aircraft also are being upgraded with satellite communications capabilities. Northrop Grumman is developing an extremely high frequency satellite communications system for the U.S. Air Force’s B-2 stealth bomber. The system is designed to enable the B-2 to send and receive battlefield information up to 100 times faster than its current satellite communications system and allow the bomber to connect to the Department of Defense’s Global Information Grid. EMS provides the antenna system and radome for the B-2 upgrade project. “The B-2 bomber is a good example of the need for satcoms,” says Smith. “Currently, the B-2 doesn’t have a satellite link and it can take a while to download target information, making it more difficult to fulfill its mission.”

Also central to the delivery of next-generation satellite services to the military is the Advanced Extremely High Frequency (EHF) constellation of satellites being built by Lockheed Martin. Three satellites will blanket the earth with global beams, and eventually these satellites will handle traffic from fixed and mobile terminals on aircraft, vessels and vehicles. The first satellite is being tested, and launch is scheduled for late 2008. The U.S. military also will invest $300 billion throughout the next 10 year in a program known as the Future Combat System, which will redefine weaponry and how the military communicates.

Smith also oversees a classified project for EMS which links F-22 fighters together with pencil-sized beams of radio frequencies. Among other things, the system allows a single plane to fly 50 miles in front of its squadron and control and fire the weapons systems in the aircraft to the rear. In concept, the network is much like a wireless LAN. Adding a satellite link will leverage the wireless infrastructure that already is in place and enhance its capabilities. Sending live video from any warplane is the goal, and a significant amount of research and development dollars is being directed toward the development of satellite communications systems for fighter aircraft.

The uptake of satellite communications equipment in the aviation market will drive improvements in technology and will eventually drive equipment footprints and hardware pricing down, expanding the market even more.

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