Shiny new Space Fence to monitor orbiting junk, satellites

NASA, Northrop Grumman others looking to protect space as number of debris as small as half an inch exceeds 300,000

Some work has begun on tracking and detecting the overabundance of space junk which has become a growing priority as all manner of satellites, rockets and possible commercial space shots are promised in the coming few years.

Today Northrop Grumman said it grabbed $30 million from the US Air Force to start developing the first phase of a global space surveillance ground radar system. The new S-Band Space Fence is part of the Department of Defense's effort to track and detect what are known as resident space objects (RSO), consisting of thousands of pieces of space debris as well as commercial and military satellites. The new Space Fence will replace the current VHF Air Force Space Surveillance System built in 1961.

According to, the current Space Fence includes nine sites located on a path across the southern United States from Georgia to California along the 33rd parallel and consists of three (3) transmitter and six (6) receiver sites. The main transmitting station located at Lake Kickapoo, Texas, has an average power output of 766,800 watts feeding a two-mile long antenna array. It provides the primary source of illumination. Two other transmitting stations are located at Jordan Lake, Alabama, and Gila River, Arizona. These stations, with average power output of approximately 40,000 watts each, improve low altitude illumination at the sides of the main beam.

Australia is a candidate for the first new Space Fence location. Two additional sites in other parts of the world are also under consideration, Northrop stated.

The Space Fence will provide continuous space situational awareness by detecting smaller objects in low and medium earth orbit. The current system requires constant sustainment intervention to maintain operations and does not address the growing population of small and micro satellites in orbit, Northrop stated.

"The new Space Fence system will provide better accuracy and faster detection while allowing us to increase the number of satellites and other space objects that can be detected and tracked, thus avoiding collision and damage to other satellites," said Rich Davis, director of special projects at Northrop Grumman's Advanced Concepts and Technology Division. This contract

The need for such a system seems obvious especially since the Iridium satellite smacked into an inactive Russian Cosmos-2251 military satellite in February. In April, NASA’s Nicholas Johnson, Chief Scientist for Orbital Debris at the Johnson Space Center told a congressional hearing that the United States Space Surveillance Network, managed by U.S. Strategic Command, is tracking more than 19,000 objects in orbit about the Earth, of which approximately 95 percent represent some form of debris. However, these are only the larger pieces of space debris, typically four inches or more in diameter. The number of debris as small as half an inch exceeds 300,000. Due to the tremendous energies possessed by space debris, the collision between a piece of debris only a half-inch in diameter and an operational spacecraft, piloted by humans or robotic, has the potential for catastrophic consequences, he stated.

The near-Earth space debris environment ranges in altitude from 100 to more than 20,000 miles above Earth, and the debris itself ranges in mass from less than an ounce to many tons. Consequently, this population of space debris is a matter of growing concern for all space-faring nations, Johnson stated.

According to Johnson, during 2008, NASA twice maneuvered robotic spacecraft of the Earth Observation System in low Earth orbit and once maneuvered a Tracking and Data Relay Satellite in geosynchronous orbit to avoid potential collisions. Twice since last August, the International Space Station has conducted collision avoidance maneuvers.

For the 35 years from mid-1961 to mid-1996, the population of cataloged objects that are four inches in size or larger in Earth orbit increased at an average rate of 270 per year. However, with the concerted efforts of the major space-faring nations of the world, the rate dropped dramatically to only 70 per year for the next decade.

Unfortunately, the intentional destruction of the Chinese Fengyun-1C weather satellite in January of 2007 and the accidental collision of American and Russian spacecraft in February of this year have increased the cataloged debris population by nearly 40%, in comparison with all the debris remaining from the first 50 years of the Space Age, Johnson stated.

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