11 November 2012

Atmospheric CO2 risks space junk build-up

Agençe France-Presse
Increasing levels of carbon dioxide in the upper levels of Earth's atmosphere risks causing a faster accumulation of man-made space junk, scientists said.
Lower Earth Orbit space junk

Computer-generated image of objects in Earth's lower orbit that are currently being tracked. Approximately 95% of the objects are orbital debris – not functional satellites. The orbital debris dots are scaled to optimise their visibility and are not scaled to Earth. Credit: NASA/JSC

PARIS: Increasing levels of carbon dioxide in the upper levels of Earth’s atmosphere risks causing a faster accumulation of man-made space junk, scientists said.

While it causes warming on Earth, CO2 conversely cools down the atmosphere and contracts its outermost layer, the thermosphere, where many satellites including the International Space Station (ISS) operate, said a study published in the journal Nature Geoscience.

A contracted thermosphere, in turn, reduces atmospheric ‘drag’ on satellites. This drag is what causes satellite orbits to change, drawing them closer to Earth, which means that orbiters like the ISS have to boost themselves back on course with on-board engines.

Many more ‘near-misses’

Commenting on the paper, space expert Hugh Lewis, from the University of Southampton in the U.K., said a cooler troposphere will extend the lifetime of space junk – staying farther out for longer instead of burning up in the lower layers of the atmosphere, closer to Earth.

“Consequently, space junk will accumulate at a faster rate and we will see more collisions between space objects as a result,” he said.

“We will also see many more ‘near-misses’ and these have an important effect on spacecraft operators.”

Plus side: satellites can carry less fuel

Lewis said there would be no increased risk for us on Earth as the rate at which satellites re-enter would be reduced.

“However, we would see some effects on services provided from space if an important satellite was destroyed by a collision,” he said.

On the positive side, satellites would no longer need to boost themselves back into orbit quite as often, meaning they can carry less fuel.

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