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Space Fence reinvented

U.S. wants ground-based network to see tiny objects in orbit

Oct. 1, 2008 - 03:45AM   |  
By Jim Hodges   |   Comments
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When the U.S. Navy started bouncing radio waves off Russian satellites to track them, there wasn't much for its new Space Surveillance System to see.

But even when the space catalog had only one item in it Sputnik launched in October 1957 the Navy saw the future. Within a year of Sputnik's launch, officials began working on the series of radar transmitters and receivers that would be known colloquially as the Space Fence.

"There became a lot of concern that, ‘Hey, there's a lot of space up there, and we have no idea what's in it,'" said Air Force Lt. Col. John Brendle, who manages what is now the Air Force Space Surveillance System at Hanscom Air Force Base, Mass. The Navy declared the surveillance system operational in 1961, and the Air Force took over the program in 2004 at the direction of then-Defense Secretary Donald Rumsfeld.

Other U.S. sensors look at spacecraft in more detail, but the Space Fence is the primary reason the U.S. government's space catalog has grown to about 10,500 objects.

The Air Force is showing fresh interest in the fence because it is the service responsible for protecting America's spy satellites, the Global Positioning System constellation and U.S. commercial satellites from orbital debris and from a new breed of microsatellites that could be equipped to harm them.

The Air Force plans to revamp the Space Fence by 2015 with more powerful radars and sites overseas for more expansive coverage. The service is inviting companies to compete for the work, and it expects to award a contract Feb. 25. The total cost is expected to be about $1 billion, including $350 million in an initial concept development phase.

Observers expect Northrop Grumman, Lockheed Martin and Raytheon, which have researched Space Fence improvements under initial study contracts, to be the primary bidders.

Advocates said a new Space Fence is necessary because the smallest satellites are too tiny for the current system to see. "There are 10-centimeter satellites in orbit today," Brendle said. And there is a growing threat from orbital debris, such as the pieces left over when China destroyed one of its dead weather satellites in 2007 to demonstrate an anti-satellite missile.

A better Space Fence is expected to expand the space catalog to more than 100,000 objects.

The Space Fence is the oldest segment of the nation's system for tracking objects in space that doesn't involve a telescope. It is a system of three VHF radar transmitting stations and six receiving stations spread roughly along the 33rd parallel from Tattnall, Ga., to San Diego. The system costs about $33 million a year to run, with most of the money going to power the radars. Its most powerful transmitter is at Lake Kickapoo, Texas, where an output of 766,800 watts feeds a two-mile-long antenna array.

The Space Fence's radar provides a continuous wave or fence over the U.S. that detects basketball-sized or larger objects passing on orbits as high as 15,000 nautical miles above Earth. It logs more than 5 million detections a month and sends its data to a Navy center in Dahlgren, Va.

The cluttered space situation might only get worse. In January 2007, a Chinese anti-satellite missile hit an old weather satellite 504 miles up, adding another 1,000 objects to the space catalog. No one knows how many pieces from the kill might be too small to be detected by the fence but big enough to damage orbiting satellites. "That stuff is going to take years, maybe decades, to fall out of orbit," Brendle said.

The debris, the trend toward smaller satellites and an increasing concern about threats in and from space have captured the attention of the Defense Department and Congress. The phrase "Space Situational Awareness" is becoming doctrine, and the National Defense Authorization Act of 2008 directed the Defense Department to "develop a strategy, to be known as the Space Protection Strategy, for the development and fielding by the U.S. of the space capabilities that are necessary to ensure freedom of action in space." A representative from the House Armed Services Committee said the space protection strategy will be classified when it is sent to Congress.

The budget request for 2009 marked a dramatic turnaround for the fence, with the Pentagon almost tripling the $14.7 million planned for it in the 2008 long-range spending plan. Not that long ago, defense officials gave thought to abandoning the fence altogether in favor of other surveillance systems. The Air Force rescinded a contract that the Navy had awarded to Raytheon in 2002. The Pentagon reduced allocations requested by the Air Force in 2005, 2006 and 2008, although Congress restored most of that money.

Now, the Pentagon's spending plan includes about $350 million in development funding for the Space Fence over the next few years. By the time it becomes operationally capable in 2015, the price tag is expected to exceed $1 billion.

What that would buy is a clearer view in space. Lockheed Martin, Northrop Grumman and Raytheon have been conducting initial risk-reduction studies of what a better Space Fence might look like. "We've been working with the Air Force on what is possible," said Scott Spence, Raytheon's program director for the Space Fence.

What the Air Force and contractors have come up with is a three-site system in which each site sends and receives S-band radar. With more power and smaller waves than the current VHF radar, the fence is expected to be able to detect objects as small as 5 centimeters in diameter slightly larger than a golf ball deeper into medium-Earth orbit, where GPS satellites travel. Rather than the current three transmitting sites and six receivers, only one radar transmitter will be in the U.S., likely at Lake Kickapoo. Dispersing the other sites around the globe would allow the fence to better track changes in orbits, which can yield important intelligence about satellites.

The Air Force is negotiating for foreign sites now and would not say where they would be located. "We need the first host nation agreement in place by 2010 so we can start planning," Brendle said. "The second would be shortly thereafter."

The capability of the new fence would carve out a new role for it. The current fence is largely a cataloging device, but the new fence "would become more of a part of the decision-making process," said Rich Davis, Northrop's director of space projects, comparing space protection to intelligence networking in conventional wars. "Now, if you go to war, you have data from the Global Hawk, from various [unmanned aerial vehicles] and from other assets," he said.

The Air Force has other systems for space surveillance and is growing even more, including the eagerly awaited Space Based Surveillance System, a Boeing satellite that is expected to be launched in January. Its 500-pound camera will help track objects in space and will complement other systems, including the Space Fence.

The SBSS is expected to be particularly valuable in tracking geosynchronous orbits that elude the Space Fence and other systems.

The aim is to be able to assign a signature, or fingerprint, to a satellite, much as sonar does to a submarine. The elements of that signature include such things as country of origin, orbit pattern, capability and intent, which are largely the elements of Space Situational Awareness.

The Space Fence would join other systems in determining that awareness. "The new Space Fence is going to have to be built to take into account existing systems and those systems that are to come," Davis said.

Raytheon's Spence agreed. "Technological advancement is going to continue, and the Space Fence is going to have to be flexible to take advantage of that advancement," he said.

The Air Force wants "to build it so that it can be updated at a later date to add power to see an even smaller object if so desired," Brendle said.

"Many more countries have the capability to launch into space," Brendle said. "Plus now you have direct defense [anti-satellite] weapons. We need to know what's there."

And what's coming in the future.

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