4 Million Pounds of Space Junk Polluting Earth’s Orbit

Millions of nuts, bolts, pieces of metal and carbon, and whole spacecraft from thousands of missions and launches form an orbiting garbage dump spinning around the Earth at speeds up to 22,000 mph.

After the recent collision between a Russian and U.S. satellite, concern for the growing hazard of space junk is becoming even more acute within the international space community. In recent months, NASA and the European Space Agency have both diverted resources into monitoring space debris and researching ways of mitigating and—some day—removing it.

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Monitoring the space environment

Using an arsenal of ground-based radars, optical telescopes and forensic spacecraft observations, the NASA Orbital Debris Program Office estimates that 19,000 objects larger than 10 centimeters in diameter are known to exist. But the estimated population of particles between 1 and 10 centimeters is 500,000 and the number of particles smaller than 1 centimeter probably exceeds tens of millions, say scientists.

One particular study estimated that there are four million pounds of space junk orbiting in low-Earth orbit and any one of the pieces could potentially threaten spacecraft, the lives of astronauts, or any number of the spacecraft studying changes in our planet and atmosphere. And the debris that could potentially threaten the lives or the viability of a space mission need only to be the size of a raisin. As an example of the hazard, a tiny speck of paint from a satellite once dug a pit in a space shuttle window nearly a quarter-inch wide.

The good news is that most space junk is located between 550 and 625 miles above the Earth — the International Space Station flies in orbit at 250 miles above Earth, while space shuttles usually only reach about 375 miles high. The bad news, however, is that a recent NASA study forecast a ten-fold increase in the probability of collision with debris over the next 200 years.

Debris increasing exponentially

What makes the 21st century problem of space junk particularly intractable is that it will likely get worse before it gets better. Many orbital debris analysts point out that current forecasts may not give a complete picture as they assume no increase in the rate of space expeditions. Current predictions were also made prior to the 2007 intentional destruction of a Chinese weather satellite. The Chinese ASAT test deposited more than 2,300 pieces of debris larger than 10 centimeters into some of the most heavily used orbits where the world’s weather and climate monitoring satellites reside.

The satellite breakup and resulting debris cloud was “the most prolific and serious fragmentation in the course of 50 years of space operations,” according NASA’s Nicholas Johnson, Chief Scientist for Orbital Debris.

While overall levels of space debris are somewhat manageable at this time, many scientists believe there is a looming problem on the horizon, as escalating amounts of debris are located in the most heavily used orbits. Even if there were no more new pieces of debris added to the orbiting space junk cloud, the total number of bits hurtling though Earth’s orbit would continue to rise as larger pieces break apart.

“There is an emerging consensus among the technical community that simply preventing creation of new debris is not going to be enough,” said Brian Weeden, Technical Consultant for the Secure World Foundation.

Weeden says that up until now, the debris mitigation process has been focused mainly on the technical aspects, but more and more attention is now being paid to the legal dimensions of space debris. A first step towards this end was the recent establishment of the United Nations Space Debris Mitigation guidelines.

“At some point we will need to actively remove debris from orbit. Fortunately, new studies are showing that removing as few as five or six objects per year could stabilize the debris population over the long term,” said Weeden.

“The big question right now,” added Weeden, “is which objects to remove first and what is the best method to do so.”

Images via NASA
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