Designing a satellite to hunt small space debris

A University of Alaska Fairbanks scientist is participating in a U.S. government effort to design a satellite and instruments capable of detecting space debris as small as 1 centimeter, less than one-half inch.

Debris that small, which cannot currently be detected from the ground, can damage satellites and other spacecraft in low-Earth orbit.

The idea is to outfit future satellites, such as those vital for communication systems, with technology to avoid space debris collisions.

Space debris travels at high speeds, about 17,500 mph. A 1-centimeter object traveling at that speed has an impact energy equivalent to that of a small explosive such as a hand grenade.

Space debris comes in many shapes and sizes and consists of defunct satellites, spent rocket stages, fragments from collisions, and other human-made objects that no longer serve a purpose.

UAF Geophysical Institute research professor Paul Bernhardt and colleagues from the University of Calgary in Canada have devised a method to determine a small object’s distance from a satellite or spacecraft and the angle of its approach.

The method is based on their discovery that an object in orbit creates waves as it passes through naturally occurring plasma disturbances—known as striations—that occur along Earth’s magnetic field lines. Plasma is a gas-like state of matter made of free-floating negative electrons and positive ions.

Bernhardt and colleagues are developing the instruments that would use that method. He is also designing the satellite that will carry the instruments for this initial test. He calls it the Space Debris Hunter.

“The whole satellite will be dedicated to detection of space debris too small to be seen from the ground,” he said.

The direction to a piece of space debris would be determined by an on-board sensor that simultaneously measures electric and magnetic wave fields to detect signals emanating from the space object. A separate sensor would record changes in signal frequency over time. Analysis of these data would then be used to determine direction and distance to the space debris to reveal its location.

“Several measurements of this type are sufficient to predict the future path of the debris,” Bernhardt said. “That’s the new science we’re exploring.”

That knowledge will allow satellites to be steered away from the path of the debris, Bernhardt said, adding that operators of the Starlink system take more 20,000 collision avoidance actions per year.

The new detection method was detailed in a Jan. 8 paper in Physics of Plasmas. Bengt Eliasson of the University of Strathclyde in Great Britain is the lead author.

The work is part of a U.S. government effort to track space debris. It was performed in collaboration with contractor Blue Halo in the IARPA Space Debris Identification and Tracking program.

The U.S. debris-tracking program estimates that more than 100 million objects greater than 1 millimeter in size orbit the Earth, but that less than 1 percent of debris that can cause mission-ending damage is tracked. Because of that, the program’s website states, “there is an increased interest” in tracking small debris.