The United States is planning to shut down a key component of its space surveillance network that tracks satellites and "space junk" orbiting the Earth. As a result, satellite launches and flights to the International Space Station (ISS) may involve a higher degree of risk.

The Air Force Space Surveillance System known as Space Fence consists of three two-mile-long transmitter antennae and six receivers in the south of the country. It has been scanning the near-earth space for any orbital objects flying over America since the 1960s.

The Air Force Command has decided not to prolong a contract with the system's current operator. The company has until October 1 to remove its staff from all of the Space Fence facilities, at which point are going to be switched off. So far, it's unclear whether the system will be dismantled.

The Space Fence can detect space objects as small as 10 cm (four inches) in diameter and thousands of larger objects, including lots space debris circling our planet and posing a serious threat to satellites and the ISS. The latter receives warnings from Earth, which enable it to maneuver to avoid collisions with space junk.

The system's shutdown is unlikely to affect the ISS crew as other systems will start watching the orbit more thoroughly, Yuri Karash, a US-trained space expert and journalist and a corresponding member of Russia's Tsiolkovsky Academy of Cosmonautics, said in an interview. Russia will share its orbit surveillance data with the United States, he said, as in all that concerns crew safety the Russian and US interests overlap.

"Russia has the Okno ["window"] system whose key component is deployed in Central Asia. Also, there are similar systems within NASA's competency framework. So, I am absolutely sure that the closure of the Space Fence will not cause any potential threats to the ISS crew.

Igor Afanasyev, editor at the News of Cosmonautics magazine, drew attention to some peculiarities of the Space Fence.

"Whatever they say about the 'fence', the main advantage of this system is that it tracks objects at heights of up to 24,000 km, while the ISS has a significantly lower orbit. The other systems scan the near-Erath space within a radius of up to 1,000 km. So, I see no reason why the risk should increase," he told a VoR correspondent.

Not all experts share his view. Mike Coletta, the owner of the satwatch.org website, notes that the Space Fence requires no selective targeting. Its radars operate round the clock, detecting any object within their field of vision.

The system has made it possible to locate many pieces of the space rubble resulting from two incidents that led to a sharp increase in space junk - an anti-satellite weapon test by China in 2007 and a collision of a Russian and US satellites in 2009.

With the Space Fence out of service, it will be harder to predict the trajectories for space junk, particularly in the "busy" orbits used by the ISS.

The US Air Force Command has blamed the Space Fence shutdown on the sequestration, an argument that doesn't sound convincing, given the modest $14 million in annual allocations for the system.

Experts at the Rand Corporation believe that all that talk of the Space Fence closure is nothing more than an attempt by the industrial lobby to press Congress and the Pentagon into approving $3 billion in funds for a space surveillance network of a new generation.

Lockheed Martin and Raytheon have reportedly been entrusted to design the new system, which may be put into service in 2017.

However, with the space junk problem looming large, there still is a chance of preserving the Space Fence. Maybe, the military should follow the advice of UniverseToday.com and just go hat in hand to try to raise $14 million?

Voice of Russia