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March 1, 2024

Finding new ways to detect space threats

By BARBARA HOLT | March 14, 2013

Seven thousand tons of dense rock hurtles towards the Earth in a fiery cloud, exploding into smaller fragments about 20 to 30 miles above the Earth’s surface. The sheer force of the meteor’s impact with the atmosphere results in a blinding flash and releases the destructive blast of a sonic boom, shattering glass and triggering alarms for miles and miles around.

While this may sound like the familiar opening to your typical science fiction film, this is precisely what occurred over Chelyabinsk, Russia on February 15.

Due to the Chelyabinsk meteor’s unusually hard composition, approximately 5 percent of its mass evaded disintegration within the Earth’s atmosphere and deposited itself upon the Siberian landscape. Over 1,000 people were injured as a result of this minute fraction alone.

A mere 13,000 miles above the planet, inside the orbit of Earth’s communication satellites, a football stadium-sized asteroid was simultaneously passing by. The asteroid, dubbed 2012 DA14, was three times the Chelyabinsk meteor’s size, measuring an approximate 150 feet in diameter.

The last time an asteroid of 2012 DA14’s size struck Earth, which occurred as recently as 1908, the 220 million-pound asteroid flattened an area of 800 square miles across, roughly the size of Washington D.C., after exploding five miles above the ground with an energy blast equivalent to 185 Hiroshima bombs.

Occurring likewise in Siberia, the resulting shock wave registered a 5.0 magnitude reading on the Richter scale from as far away as Great Britain.

“The threat to on orbit satellites is very, very small...their cross section and the NEO coming though being small cross section makes it a low probability,” John “Jack” Anthony (Colonel, Retired), former Commander of the United State’s Air Force’s 1st Space Operations Squadron and current leader of the Air Force Academy’s satellite engineering program, said. “However, the energy dissipated in the entry and impact is tremendous, that’s a big threat.”

Even more disturbing than the threat of entry and impact, however, is our present inability to detect approaching asteroids before it’s too late. While NASA can account for 90 percent of all larger space objects near Earth, the 10,000 tracked asteroids only account for 1 percent of the total estimated asteroid population. Fortunately, several initiatives in response to the threat are already underway, with even more proposed ideas for future technology.

Space-field experts insist the key to defending Earth from asteroids is early detection. Since the viewing potential of Earth-based telescopes is limited by the obscuring atmosphere, the best bet for improving our detection ability seems to be moving telescopes into space.

“There is tremendous use of ground based telescopes scanning the outer region for these objects, and there are initiatives to build and operate space-based sensors to see even smaller objects,” Anthony explained. “Upon discovery, astrodynamics experts can model the trajectory and see if there is potential for collision.”

Sentinel telescope, currently under development by the private B612 Foundation, is a 0.5 meter diameter infrared telescope designed to orbit between Earth and the Sun. Looking outward at the asteroid swarm, it should be capable of tracking 90 percent of all potentially hazardous objects larger than 460 feet.

In the event that a threatening asteroid is identified, the focus must then turn to deflection. Simply exploding an asteroid would not guarantee the Earth’s safety, as even a nuclear warhead may not be able to disintegrate its material into small-enough fragments.

Instead of destroying the asteroid, experts believe the most viable option is to alter the asteroid’s trajectory so precisely that it both misses Earth and avoids “boomeranging” back around the Sun and into another collision path.

As with detection technologies, proposals for asteroid deflection technology abound. However, the simplest solutions are often the best.

One promising idea involves the use of a “gravity tractor,” a giant spacecraft that would shepherd an asteroid in the desired direction using the gravitational attraction of its mass.

Less precise possibilities include slamming a spacecraft into the asteroid, detonating a nuclear bomb in the vicinity, and accelerating debris in a specified direction to achieve opposing force.

“It’s not an easy chore and it’s fraught with risk. But, viable ideas are being considered,” Anthony said. “I have faith in the scientists and engineers who would be predicting that...we’d need to trust them.”

 


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