WASHINGTON -- Space gridlock. It’s not quite solar-panel-to-solar-panel traffic above Earth -- but it is getting crowded as more and more nations vie for their own space byways.
In a decade’s time, nearly 1,500 active
satellites are expected to be circling our planet. That is more than twice the number beeping away today.
What may be needed is something akin to air-traffic control, but built for day-to-day steering of satellites, piloted shuttles and occupied
space stations.
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After all, a
fender bender at spacecraft speeds is no minor violation. It would be a ticket to disaster.
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The MSX satellite has spotted upwards of 100 space objects that had been lost. |
Spotter scope
A step in the direction of space-traffic control is use of the Midcourse Space Experiment (MSX) satellite. The just-under $1 billion Pentagon satellite was launched in April 1996. The spacecraft was built and equipped to carry out studies for the Ballistic Missile Defense Organization.
During its primary mission, the MSX used a super-cooled infrared sensor to detect and track test warheads that were sent skyward from Earth. That duty ended in February 1997 as the satellite’s on-board coolant supply used to chill the infrared instrument ran out.
However, a host of other sensors on the spacecraft remain fully functional.
One of those devices is the Space-Based Visible Sensor. Built by the Massachusetts Institute of Technology’s Lincoln Laboratory in Lexington, the optical sensor is being used to scan deep space.
The hunt has paid off.
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"We’re coming up to 150 objects in the last three years that were completely lost, or nearly lost," said Curt von Braun, program manger for the MIT Lincoln Laboratory Space-Based Visible Sensor. "We’re blazing a trail here. Nobody else has done this before. This is the only operational space-based space surveillance instrument," von Braun told SPACE.com.
Lost and found department
From the MSX vantage point -- now orbiting at 559 miles (900 kilometers) above Earth -- big chunks of space debris and derelict rocket bodies have been spotted, as have scads of Russian payloads and a host of commercial communications satellites, some of them wandering aimlessly through space.
The satellite sensor has proven most helpful in keeping an eye on highflying spacecraft, particularly in geosynchronous orbit -- some 22,300 miles (35,880 kilometers) above the planet. At that altitude a belt of satellites from a variety of nations coexist.
The
Air Force Space Command has a tough time cataloging and tracking objects in geosynchronous orbit using their network of ground equipment, MIT’s von Braun said. That ground-up view is also limited by location, weather and time of day.
Some satellites can drift away from their last known position. "It becomes a needle in a haystack at that point," von Braun said.
Bump-free belt
For the last three years, the MSX space-scanning sensor has reduced the number of lost satellites in key orbits from 63 to 13, said Roger Sudbury, a spokesman for Lincoln Laboratory.
Given the ability of MSX to better track objects in high-altitude satellite orbits, the spacecraft has been handed over to the Air Force Space Command. It is now part of the Space Surveillance network, Sudbury said.
Von Braun said use of MSX for space surveillance from orbit has had a big impact.
The U.S. Air Force would like to begin orbiting a small constellation of spacecraft by 2010, said von Braun, tasked to keep an eye on the surrounding space that each satellite zips through -- over and under.
Can a space-based satellite-traffic control system be far behind?
"I think it’s possible. This is the beginning of such an idea. You obviously have to know where everything is," von Braun said.
While a dedicated space-traffic control may be many years off, von Braun said that keeping an eye on geosynchronous orbit is a start.
"Everyone in the geosynchronous belt has certain positions that they’ve been allocated. Each entity must remain within those positions. Nobody wants to bump into other things," von Braun said.
At present, the Air Force Space Command in Colorado Springs, Colorado has the charter to keep an eye on the whirling whereabouts of both military and civilian spacecraft, as well as chunks of space junk.
"Traffic control is a term used quite often, in conceptual terms. We don't really know what that term means as yet," said Nicholas Johnson, chief scientist in NASA's orbital debris program office at the Johnson Space Center in Houston, Texas.
At what time the capacity of the current network of ground-based sensors might be exceeded is unknown, he said.
Orbital tracks of the space shuttle and the International Space Station are closely monitored, Johnson said.
Program managers are advised of any collision avoidance maneuvers that may be required.
In the past, Johnson said, several shuttle orbiters had to jet themselves out of harms way to avoid any prospect of running into derelict debris. "But very few other spacecraft ever do that," he said.
MSX has proven the concept of space-based space surveillance, he said. However, space-traffic control is not, at this time, a pressing issue, Johnson said. "My personal assessment is that it's going to be a few more years before people get serious about what we really need to do for the long term."
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