Space: Bandwidth Blues


April 30, 2007: About three years late, the U.S. Department of Defense is ready to launch its first new communications satellite. These WGS (Wideband Gapfiller Satellite) are actually modified versions of the Boeing 702 communications satellite. Boeing has orders for 19 of these, which are built on the earlier, and very successful, 600 series communications satellites.

Seemed like a slam-dunk, basing needed military commo birds on a solid civilian model. A few tweaks and additions to deal with military security needs, and off we go. The Department of Defense wants to build six WGS birds, at a cost of some $220 million each. The WGS has ten times the throughput (three gigabits) of the earlier DSCS III commo satellites. The first WGS bird in orbit would more than double the transmission capacity of the Department of Defense satellite system.

There is a growing need for more commo birds. Between 2000 and 2002, Department of Defense satellite bandwidth (data transmission demand) doubled, and more than doubled every 18 months after that. Back in 2000, some 60 percent of Department of Defense satellite capacity had to be leased from commercial firms. While the Department of Defense had it's own communications satellite network (MILSAT), it underestimated the growth of demand. Greater use of the internet and reconnaissance aircraft and UAVs using video cameras quickly used up MILSATs capacity and forced the military to lease capacity on commercial satellites. This was done on the "spot market," meaning the Department of Defense had to pay whatever the market would bear at that moment. Since the military needed more capacity because of combat operations, the media was also in the market for more capacity to cover the war. The Department of Defense paid more than ten times as much as it would have if it had leased (for one to fifteen years) satellite capacity earlier. The situation was made worse by the fact that it was an emergency situation, so every heavy user of satellite communications was making their own deals. This resulted in some users (air force, or, say, the Atlantic Fleet) having some extra capacity when someone else, like Army Special Forces, was still short.

During the 1990s, the U.S. armed forces moved to satellite communications in a big way. 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, less than half 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.

With the growing number of UAVs, ship, ground vehicle and aircraft requirements for bandwidth, the Department of Defense expects to need more than 16 gigabits (thousand megabits) by 2010. Thus the rush to get those WGS birds up.

Attempts to get capacity from civilian satellites was complicated by the fact that there was a shortage there as well. This was created by the tremendous overbuilding of fiber optic cable networks on the ground (and under oceans) in the late 1990s. This provided cheaper bandwidth for civilian uses and has meant fewer communications satellites being put up. In fact, the fiber optic glut reduced planned satellite launches by some 60 percent for the first few years of this decade.

The solution was the WGS birds, with the first one going up in 2004. But there were design problems, manufacturing problems, and scheduling problems getting an American launcher (having a Russian or Chinese rocket put these birds into orbit was not an option, for security reasons.) These problems have been solved, and two WGS birds will be launched this year, with another next year, and the remaining three by 2013. That will provide nearly 20 gigabits of capacity, which will still not be enough.


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