Prof Calls Space an Increasingly Crowded Place

The collision of two satellites above Siberia prompted concerns of a future cascade of crashes, and one space scientist says the vastness of space is getting cozier by the day.

“The North American Aerospace Defense Command tracks everything orbiting the earth much larger than about 3 cm, which is pretty small,” said Dr. Marc Hairston, research scientist at the UT Dallas William B. Hanson Center for Space Sciences. “Around 15,000 objects consisting of satellites, pieces of debris and even tools and tool bags left in space are being constantly monitored to watch for potential collisions.”

Getting crowded: A graphical simulation shows the cloud of satellites and debris in low Earth orbit. (Illustration courtesy of the NASA Orbital Debris Program)

Hairston and other space scientists believe the recent fireball in the skies above central Texas was a meteor and not satellite wreckage, but he says debris and objects orbiting the Earth will be around to create crash hazards for tens, if not hundreds of years.

“When objects collide in space, they produce a cloud of debris that spread out along the original orbit, and these debris threaten other functioning satellites,” Hairston said. “Something the size of a penny, or even much smaller, that is traveling at five miles a second can smash straight through another satellite and wreck havoc on electronics and other critical components.”

Hairston and a team led by Center for Space Sciences Director Dr. Roderick Heelis study the ionosphere with the Coupled Ion-Neutral Dynamics Investigation (CINDI) team. The debris trail from the satellite collision prompted concern for the long-term safety of the satellite that bears the CINDI instruments. The conditions of the upper atmosphere that are studied by CINDI have a direct effect on how long space debris remains in orbit.

“The Air Force and government labs have developed sophisticated programs for predicting the future paths of these debris to see if they could hit the space shuttle, the International Space Station or other crucial spacecraft,” Hairston said. “But these models are only as good as the data about the atmosphere that go into them. CINDI is helping us map and give real-time information about the critical physical parameters these models need.”

According to Hairston, the vastness of space offers ample room for satellites, but the increasing amount of space debris makes the likelihood of future catastrophic collisions almost a certainty.

“A rare set of circumstances have to fall into place for two objects in space to collide—it is like hitting a bullet with a bullet,” Hairston said. “Had the Russian satellite and the Iridium satellite missed each other by only 1/1000th of a second, they’d have missed each other by 7 meters (close to 21 feet) and nothing would have happened. But now that one of the satellites has been turned into a cloud of space debris, it’s like hitting a bullet with a thousand pieces of high-speed buckshot. The odds of a collision go up.”

Hairston warned that the other 65 Iridium satellites and all other satellites that orbit at altitudes of about 500 miles are at an increased risk after last week’s collision, and this higher risk will last for several years.

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