Sending data with lasers, rather than radio frequencies, has the potential to revolutionize the way the military communicates, proponents of the technology have said.
Laser communications, which transmits ones and zeroes in a data stream through narrow beams of energy, is not unlike widely used fiber-optic cable — it just doesn’t have the cable.
The military has been looking at “free-space optical communications” — the more technical term — for decades. Several defense contractors, meanwhile, have been investing their own dollars to develop laser communication applications — everything from blue-force tracking in small squads, to links between unmanned aerial vehicles and satellites, as well as communications on the move for ground troops riding in combat or tactical wheeled vehicles.
One vendor said it has already been fielded with a U.S. government customer he could not disclose.
NASA recently began a project to demonstrate how it can use the technology to link Earth-based ground stations to spacecraft traveling millions of miles away in the solar system.
Contractors say after years of development, the technology is ready to be widely fielded.
“We’re talking data rates that can be 100 to 1,000 times or more greater than what you can get with [radio frequency] data links,” said Michael Perry, vice president of the laser-electric optic business unit in General Atomics Aeronautical Systems Inc.'s reconnaissance systems group. The UAV maker is partnering with a German satellite company to demonstrate laser links between a Reaper remotely piloted aircraft and a satellite in geo-stationary orbit some 25,000 miles above the Earth.
The finite amount of radio spectrum available to the U.S. military has been an ongoing issue. At the same time, the demand for it is insatiable. The advent of unmanned aerial vehicles that need to send live, streaming video to bases around the world has driven the high demand, and forced the military to lease time on commercial satellites. The demand is likely to increase as higher resolution, next-generation sensors that require more bandwidth proliferate in the coming years.
The overcrowded airwaves are also prone to interference, or “fratricide” as radio engineers like to call it. Adversaries can also try to intercept messages or jam signals.
Laser communications do not use any of the radio spectrum. And, advocates point out, it is inherently protected. To disrupt a transmission, an enemy would have to be able to detect the narrow beam and find a way to put an object in front of it. To actually intercept data, he would have to place a receiver in its path.
In its simplest form, the energy is transmitted in pulses with the “1” digit being a pulse and the “0” a gap. But modulating the timing can create more sophisticated pulses.
Perry described it as: “Morse code but at ridiculously high rates.”
How high? Two gigabytes per second and upwards of 20 gigabytes per second are possible, he said.
Radio frequency transmissions can go to 200 megabytes per second, but 45 megabytes is more typical, said Gary Tarantino, manager of advanced systems and strategic initiatives at ITT Exelis. ITT is working on lasers that can do communications on the move terrestrially between aircraft, ground vehicles and ships.
“You have a tremendous amount of bandwidth that allows you the flexibility to transmit the [intelligence, reconnaissance and surveillance] information in a timely manner,” he said.
The downside is that the beams can’t bend or penetrate buildings. There must be a line of sight between two points.
“Rain and fog we go through much better than people expect,” said Steve Sampson, vice president of advanced programs at Cubic Defense Applications.
Cubic is working on lasers that can do small unit blue-force tracking and tactical communications.
General Atomics, ITT Exelis and Cubic are all betting their own internal research-and-development funds on laser communications. All three will be demonstrating the technology for U.S. military customers in the coming year.
Cubic did receive seed money from the Defense Advanced Research Projects Agency to develop its dismounted combat identification system. DARPA wanted blue-force tracking capability for dismounted troops. Such systems currently are installed on vehicles, and are too bulky to be carried.
The laser is inside a rifle scope. All the troops in the unit have a small modulating retro reflector, or tag, that could be mounted on a helmet. When the directed energy hits the tag, it reflects back and shows up inside the scope as a “friendly.” Other people or objects, such as trees, will also show up, but would remain unidentified. Since the tag reflects the energy, instead of generating it, it is lightweight, about one-inch-by-one inch, and doesn’t require batteries.
“It is about as low weight and low battery consumption as anything out there,” Sampson said.
The wavelengths are not visible to any common battlefield sensors, which makes it attractive to units that carry out covert missions.
Cubic has adapted the technology for two-way voice communication, which has been sold and fielded to a government customer whom he declined to name.
On a larger scale, laser communications were once part of the Air Force’s transformational satellite program. It envisioned high-throughput military communication spacecraft using the technology. That program, however, ran into cost overruns and was canceled in 2009.
Laser communications in space are still alive, though.
General Atomics is partnering with German company Tesat Spacecom to demonstrate the linking of a Reaper unmanned aircraft with a satellite as early as the fourth quarter of 2013. Tesat is placing a laser terminal on the Alphasat, a public-private satellite being launched next year by the European Space Agency and commercial communications provider Inmarsat.
“We saw this as an opportunity to create not only a demonstration, but something that would have some enduring operational capability for the Reaper,” Perry said.
General Atomics has developed the airborne terminal that can transmit data through the energy beam to the spacecraft. It processes the information onboard, then retransmits it back to a ground station.
Laser communications allows links in environments that are “challenging for RF data links.” What those were, Perry declined to say.
ITT Exelis is working exclusively in the terrestrial realm. It is offering laser communication nodes that can be put on military platforms on land, sea and air. The company doesn’t see any utility in fixed sites, Tarantino said. It spent seven years developing with its own funds the “pointing acquisition and tracking” system that allows laser links between two moving vehicles.
“They have to be mobile systems. We don’t have a static military out there. They are moving. They are mobile,” Tarantino said.
Along with significantly higher throughput, he touted the technology’s security. The military has a renewed emphasis on anti-access/area-denial scenarios where the military may fight against peer competitors who are adept at jamming and electronic warfare. There may be situations where radios are knocked out. Laser might be the only secure way to communicate, he said.
The company has achieved air-to-air connections at 3 gigabytes per second at a distance of 130 kilometers. Air to ground reaches about 65 kilometers, and ground to ground about 35 kilometers. Because there has to be a line of sight, there must be connecting nodes, similar to radio repeaters, to expand the system over greater distances and over the horizon.
NASA, on the other hand, is looking at laser communications at distances that make these look miniscule.
For example, the Mars Reconnaissance Orbiter takes approximately 90 minutes to transmit a single high-resolution image back to Earth at 6 megabytes per second. NASA’s proposed optical communications transmitter would have the capacity to transmit data back at 100 megabytes per second or more, and to reduce the single image transmission time to about 5 minutes, according to a NASA press release. The distance between Mars and Earth averages about 225 million kilometers.
Meanwhile, the services have been clear on their needs as far as size, weight and power, Tarantino said. ITT Exelis has made the apertures as small as possible to accommodate what the military will want, although there are no formal requirements or programs of record — at least in the nonclassified world.
The four services will be coming to witness the company’s demonstrations next year, Tarantino said.
With the three companies poised to demonstrate laser communications, the question now becomes whether the military wants it, and more importantly, whether it can afford it.
All three executives acknowledged that under the current budget crunch, new, transformative technologies have been withering on the vine.
“That certainly is a big issue and we wouldn’t even be contemplating this if we didn’t have a satellite up there with a lasercom package on it,” Perry said. “These are really the first steps.”
A lasercom terminal on a Reaper is affordable “if you don’t have to purchase the satellite,” he added.
“We have been in discussions with the U.S. government and the German government as well,” he added. “We would not go forward into it without the understanding and support of the governments.”
Sampson said of the blue-force tracking system: “If there hadn’t been sequestration, I think we would have had these in the soldiers’ hands by now, but budgets have all been cut and we’re waiting to see what happens.”
Tarantino said ITT Exelis is striving to make the system affordable. Its system would not depend on satellites. “A high cost solution would not be the right approach, especially in this environment,” he added.
The Air Force, which operates most of the military’s communications satellites, does not have any new programs in the pipeline to replace the T-Sat program, said Lt. Gen. Susan Pawlikowski, commander of the Air Force Space and Missile Systems Center.
“Clearly, [laser communications] has some potential for high-capacity, high-speed communication, but I don’t have any near-term programs to use it right now,” she told National Defense.
She worked on the T-Sat program earlier in her career, and is familiar with the technology and its potential benefits.
“It certainly has a lot of promise, it is just a matter of whether we have the money to make that kind of investment,” she said. The main issue is the infrastructure change.
“We talk about satellites and payloads, but if you look at those compared to the cost of all the terminals, it is a small fraction.
“So when we talk about making a transition to something completely new like laser communication, you’re talking about a huge investment beyond just what it takes to put the payload on there.”
Steven H. Walker, the Air Force deputy assistant secretary for science, technology and engineering, testified before the Senate Armed Services’ subcommittee on emerging threats and capabilities that the Air Force Research Laboratory would be divesting its laser communications programs.
However, in June, the AFRL released a request for information seeking ideas for a space laser communications terminal for “future military satellite communication requirements.”
Laura McGowan, 88th Air Base Wing spokeswoman, said Walker was referring to reducing funding for a specific ground-based lasercom technology developed by the lab’s directed energy directorate.
Air Force investment in the other aspects of the technology is proceeding. The lab is completing work on ground-terminal technology development for high speed terrestrial laser communications.
“This is considered a mature technology and available for Air Force applications as needed,” she said.
As far as space applications, AFRL intends to continue investments at the space vehicles directorate for applications such as satellite crosslinks.
“Technology development efforts in these areas are currently funded in the future year defense program,” she said.
Photo Credit: Cubic