Tiny bits of space junk reveal their wherabouts when they collide, boffins hope
It's hard to see, but when they rendezvous in orbit sparks ignite
Tiny bits of space junk too small to track using current methods could be detected by a novel process using by ground-based radio dishes, according to the latest research.
Big pieces of space junk, like parts of spent rocket boosters or broken satellites, are easy to spot because their orbits are known and they’re big enough to get a reading on. But the millions of smaller items are harder to find, and more are appearing as large items of orbital debris slowly degrade and fragment.
Astroboffins fear that as more such objects come into existence, the risk of debris colliding to create a dangerous chain reaction is increasing. Now, a team of researchers led by the University of Michigan believe it may be possible to hunt for space junk smaller than ten centimeters across by spotting electrical pulses created when they crash into each other.
Some objects vaporize upon impact, creating charged gas and a small amount of electrical energy, explained Mojtaba Akhavan-Tafti, lead scientist on the project and a assistant research scientist in climate and space sciences and engineering at the University of Michigan.
"When the cloud of charged gas and debris fragments expands, it creates lightning-like energy bursts, similar to signals produced by static sparks that appear after rubbing a freshly laundered blanket," he said. The pulses can electrically charge other bits of nearby junk, leading to more short bursts of energy that last less than a second, but which could be detected by radio observatories on Earth.
The idea will be presented at the Second International Orbital Debris Conference this week.
"Right now, we detect space debris by looking for objects that reflect light or radar signals," said Nilton Renno, the principal investigator of the project and a professor of climate and space sciences and engineering and aerospace engineering at the University of Michigan. "The smaller the objects get, the harder it becomes to get sunlight or radar signals strong enough to detect them from the ground."
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In a research paper, the team said that some radio antennae like NASA's Deep Space Network system could be sensitive enough to measure the signals produced by small items colliding.
"We assume that the [electromagnetic pulse] signal generated at [geosynchronous equatorial orbit] is measured by a 500 MHz radio receiver with a band-width of 400 MHz connected to the [26-meter] dish, and that the [electric field emission pulse] signal is measured by an 8.48 GHz radio receiver with a bandwidth of 20 MHz like those of NASA's Deep Space Network (DSN) X-band receivers, but also connected to the 26m dish," they wrote [PDF].
The researchers are still figuring out the characteristics of these signals, by simulating different impact scenarios in computer models. They eventually want to perform real experiments and incite collisions between bits of space junk of different sizes and speeds.
The frequencies from the electrical pulses created from the reactions can then be measured and located. The boffins can then begin to analyze how different types of colliding materials might create different types of electrical signals. All that info can then be used to predict the size and orbit for newly-created space junk.
The current project is funded under the US government's Intelligence Advanced Research Projects Activity Space Debris Identification and Tracking program. The tiniest fragments of leftover junk traveling an average velocity of 22,500 miles per hour (a little over 10,000 meters per second) can damage a satellite or an ISS window, potentially frazzling GPS, other navigational or communications systems that Earth relies on.
There are reportedly over 100 million objects larger than a millimeter in size currently orbiting around our planet, but less than one percent of the debris capable of damaging spacecraft is being monitored. ®