Close call puts focus on traffic jam in space
The International Space Station’s narrow miss last week highlights the risk of collisions with space junk.
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One reason satellite-on-satellite collisions don’t occur more often is that objects are mostly hundreds of miles apart, Dr. Finkleman explains. Even a close approach doesn’t necessarily translate into a high collision risk.Skip to next paragraph
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Still, operators tend to get antsy when the risk of a collision rises above about 1 in 10,000. “The concern is protecting investment rather than a cascading catastrophe,” says Finkelman.
For NASA, crew survival is critical, so flight controllers tend to be conservative about close passes.
Satellite operators know where their satellites are, but not necessarily know where everything else is, notes Brian Weeden, a former US Air Force captain who served with the squadron responsible for tracking and cataloging objects in space. He now consults for Secure World Foundation in Superior, Colo.
The problem close to Earth is dealing with a 50-year build-up of debris and derelicts. The issue could become at least as acute in geosynchronous orbit, some 22,000 miles from Earth. There, satellites are assigned a “box” roughly 600 miles a side. An operator may put several satellites in that box. They must all keep moving to counter the tug of war between Earth’s gravity and the moon’s, while trying to stay inside the box. At that altitude, it doesn’t take as heavy a punch to cause a problem as it does closer to Earth.
Military and civilian organizations are looking at various approaches to improving the ability to track objects. One approach involves setting up a “fence” of beams from a new generation of radar that can spot debris as small as 0.4 inches, Mr. Weeden says. It would cover low and medium Earth orbits.
For the geosynchronous orbit, commercial operators have started to feed their satellites’ position to the Space Standards and Innovation Center, which then calculates likely conjunctions and their chances of leading to a collision.
The Air Force is also exploring options to serve as an international clearing house for satellite information under its Commercial and Foreign Entities Support Pilot Program. The agency has a website for publishing the orbital and other satellite information it gathers, but Weeden points out that it doesn’t represent the most accurate information the Air Force has.
The Air Force is now looking at plans to offer services such as estimates of conjunctions, support for figuring out a satellite malfunction, or emergency help if something threatens a satellite or human life in orbit.
In the end, improving space “situational awareness” has to include greater data sharing, says Weeden. As more countries loft satellites, and the risk rises of an innocent collision being mistaken for hostile action, he says, it’s becoming clear that “you can’t do it through unilateral action."