Defense News January 18, 2009
10-Centimeter Satellites
By William Matthews
Getting the 2-pound satellite into space isn't the hard part. Controlling it while it's up there will be the real challenge, Norman Fitz-Coy said.
The 10-centimeter cube-shaped satellite that sits in a University of Florida aerospace engineering lab is the latest addition to a new generation of "CubeSats" being built and launched by universities across the United States as part of government-funded efforts to inject innovation into U.S. aerospace programs.
With money from the National Science Foundation, a dozen University of Florida students built the tiny satellite and plan to launch it later this year. Total cost: about $100,000. By contrast, building and launching full-sized satellites can cost hundreds of millions of dollars.
The Florida satellite's chief task is to test a new satellite attitude controller called a "rapid retargeting and precision pointing" system, said Fitz-Coy, who is director of the university's Advanced Space Technologies Research and Education Center.
Small satellites have proved difficult to control in space.
Lacking the bulk of 5- or 10-ton communications and image collecting satellites, tiny CubeSats also lack the inertia that keeps them hurtling steadily forward, Fitz-Coy said. "The smaller they are, the more susceptible they are to disturbances."
And because they're small, they also have limited power systems. That means they have to fly at lower altitudes - about 400 miles above the Earth - to communicate with the ground. But lower altitude means they pass overhead faster, so for missions like reconnaissance, they must be able to keep sensors accurately focused on targets passing below.
Fitz-Coy thinks a compact three-axis attitude controller will be the solution. The U.S. Air Force is among those interested in how well it works, he said.
But the performance of the controller is just part of a broader experiment into how small satellites might change the nature of U.S. aerospace.
Today, satellites are basically large, custom-designed, hand-built spacecraft that are enormously expensive.
But what if satellites could be mass-produced? Cost and production time could be dramatically cut, Fitz-Coy said.
"We want to develop protocols to make it a lot more efficient. And the National Science Foundation's objective is to get to the point where we can do it really quickly."
But what is the value of a 4-inch cubic satellite?
"Size imposes limitations," Fitz-Coy conceded. Optics, for example, "need real estate." There has to be enough space on the satellite to accommodate high-quality cameras, infrared sensors, radars and the like.
Meanwhile, small batteries and tiny solar cells provide a bare minimum of electricity.
"We're trying to make existing sensors more power-efficient," Fitz-Coy said.
But there may be ways to overcome the limitations of tiny satellites by launching a bunch of them, linking them wirelessly and having them work together.
The U.S. Defense Advanced Research Projects Agency (DARPA) is examining the same idea. Its "fractionated satellite" program is examining large current-generation satellites with the idea of reproducing their capabilities using constellations of smaller satellites.
"DARPA is looking at how you might fractionate a big satellite into smaller ones. We're looking at how to use multiple small satellites" to create the capabilities of a large one, Fitz-Coy said.
In theory, at least, a "swarm" of small satellites ought to be able to do "anything you need to do with a satellite - reconnaissance, communication, blue force tracking, repeaters for global positioning satellites, communications hubs," he said.
It's unlikely that small satellites will fully replace their bigger, older counterparts any time soon. More probably, they will complement existing satellites by adding new capabilities, Fitz-Coy said.
Availability for quick launch may prove to be the small satellites' biggest appeal, said Charles Vick, a senior analyst at GlobalSecurity.org.
"They may be especially useful when you're going into a situation where some satellite has been taken out by an adversary or an equipment failure and you need a replacement immediately, even if it's only a replacement to a limited extent," Vick said.
"We have a large issue in terms of [a lack of] quick response. The Air Force has been looking at it for some time," he said.
Indeed, since 1999 the Air Force Office of Scientific Research has sponsored a University Nanosatellite Program, under which students at 25 universities across the country have designed and built small satellites.
"The technology is moving along," Vick said. "But how far along it is now is not clear."
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