Space: Smaller Satellite Substitutes

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March 7,2008: Once the troops got a taste of satellite communications in the 2003 invasion of Iraq (especially via Blue Force Tracker), there was no going back to the bad old days. Traditional military radios, be they AM (which have longer range, but variable sound quality) or FM (clear sound, but line-of-sight range, and often blocked by hills or buildings), are much less effective than a satellite based system. But the U.S. Department of Defense has known for several years that it cannot afford sufficient satellites to meet the growing demand. So the satellite transponders are now being mounted in smaller and smaller UAVs, enabling divisions or brigades to put up their own "satellite substitute," for as long as they are willing to keep their Shadow 200, or larger, UAV in the air.

Communications satellites cost at least $250 million each, and even the much touted micro-sats still cost about ten percent of that. These take years to build and launch. That's not fast enough. While weather balloons, equipped with satellite commo gear, have been suggested as high altitude "satellite replacements", there is the control problem. Even tethered balloons (they look like blimps) are vulnerable. But any "satellite replacement" is a major advantage because most of the satellite communications needed by combat troops is with other people in the same general area. So the commsat replacement (a balloon, UAV or B-52) can do the job, passing off the long distance stuff to the real commsat.

The major cause of more commsat use is live video being generated by the increasing number of vidcams on the battlefield. These vids are being exchanged by the units cooperating in an operation. Since that's all local, a "satellite substitute" (a balloon, or aircraft carrying the comm. Gear) will work. That's why comm gear in UAVs, including special UAVs that just fly circles high in the sky, is seen as an attractive satellite substitute. These substitutes cost less than ten percent, per hour in use, of what satellites cost.

The satcomm shortage problem began actually during the 1990s, when the U.S. armed forces moved to satellite communications in a big way, at least for headquarters. Most of the troops kept using the traditional AM and FM radios, This made sense, especially where troops often have to set up shop in out of the way places and need a reliable way to keep in touch with nearby forces on land and sea as well as bases and headquarters back in the United States. At the time of the 1991 Gulf War, there was enough satellite military communications capacity (commonly known as "bandwidth") in the Persian Gulf for about 1300 simultaneous phone calls. Or, as the geeks put it, 100 mega (million) bits per second. But while the military has a lot more satellite capacity now (the exact amount is a secret), demand has increased even faster. UAV reconnaissance aircraft use enormous amounts of satellite capacity. The Global Hawk needed 500 megabits, and Predators about half as much. The major consumer of bandwidth is the live video.

UAVs have other sensors as well, as do aircraft. A voice radio connection only takes about 2,000 bits per second, and each of the multiple channels needed to control the UAVs use about the same. But it adds up, especially since the military wants high resolution video. At the moment, the U.S. has far more demand for satellite communications than it can support. As a result, not all the Predator and Global Hawk UAVs in combat zones have sufficient bandwidth to send their video back to the United States. Data compression and using lower resolution is often necessary, or using satellite substitutes (aircraft carrying transponders) to send the video to local users. The substitutes are becoming more common, simply because there is neither the money, nor the time, to get sufficient satellites into orbit.

 


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