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Satellite and spacecraft operators may eventually be able to detect small pieces of debris orbiting the Earth using methods proposed by researchers at the University of Michigan.
Currently, we detect space debris by looking for objects that reflect light or radar signals," said Nilton Renno, principal investigator of the University of Michigan team and professor of climate and space science and engineering and aerospace engineering. "The smaller the object, the harder it is to get a strong enough sunlight or radar signal to detect them from the ground.
Today, objects larger than softballs are the only traceable pieces of this "space junk", nearly 1Of the 700 million pieces of garbage, less than 1%. The new method can detect fragments less than a millimeter in diameter, similar to the thickness of a pencil lead.
Renno will present the findings with Yun Zhang, a postdoctoral researcher in climate and space science and engineering, at the 2nd International Orbital Debris Conference on December 5. These results are the first to come from a larger collaborative project, the Space Debris Identification and Tracking Program for the Advanced Intelligence Research Project (AHCR) activity. The project is being led by military contractor Blue Halo, including Alaska Fairbanks University.
Junk in space is not only ugly, it's dangerous. At a typical orbital speed of 22,000 miles per hour, a piece of space debris the size of a plum can hit another object with the same energy as a car crash on a highway and could bring a satellite to a halt. Even smaller pieces of debris can damage spacecraft, so tracking them is essential for satellites and spacecraft that need evasive action.
The Earth's orbit is becoming more and more chaotic, which makes it more difficult to protect satellites. Space debris often collides with each other, resulting in larger fragments being turned into small, undetectable fragments. Some experts fear that the amount of space debris could grow exponentially as individual pieces of debris continue to collide, eventually wreaking havoc on the infrastructure we rely on, such as GPS, cell phone data, weather monitoring, and more.
While potentially catastrophic, collisions between space debris could prove to be the best way to track tiny pieces of space junk. When small pieces of space debris collide, they explode into tiny fragments, some of which evaporate into charged gases due to the heat generated by the impact.
When the charged gas and the cloud of debris fragments expands, it produces a lightning-like burst of energy, similar to the signal produced by the electrostatic spark that appears after rubbing a freshly washed blanket," said Mojtaba Akh**an-Tafti, an assistant research scientist in climate and space science and engineering and the project's chief scientist.
After this initial burst of energy, charged solid fragments can generate electric field pulses when close enough to each other, creating additional lightning-like bursts. These electrical signals last only a fraction of a second, but they can help track the space debris and microscopic debris clouds that form when the debris collides.
According to the team's recent computer simulations, when two pieces of aluminum collide at typical orbital speeds, they emit a burst of electricity strong enough to be detected from the ground by a 26-meter dish antenna with a high-quality radio receiver. Similarly, electric field pulses should be detected with more sensitive radio arrays, such as NASA's deep space network.
There's still a lot to do. The frequency of the electrical signal varies with the velocity of the collision and the composition of the debris, which can complicate detection. To see electrical signals, they need to be stronger than the background signals of ground-based instruments and pass through the Earth's upper atmosphere.
The team plans to refine their approach with additional computer simulations by measuring real-world signals through NASA's deep space network and analyzing data from ultra-high-velocity experiments at the Naval Research Laboratory and NASA Ames Research Center. Using lasers from these facilities, the team can launch different kinds of debris at targets within a range of orbital velocities and measure the electrical emission characteristics of impacts.
If these experiments reveal a method for detecting various electrical signals generated during the collision of space debris, they can determine not only the location of space debris, but also its appearance and composition.
We want to know if an object is hard or soft, because that affects its orbit as well as how destructive it is," said Akh**an-Tafti.
More information: Research: "Non-thermal electromagnetic radiation from space debris collisions" (3 p.m. Beijing time, 3 p.m. Beijing time, 5 December, IOC SINTRA meeting).