NASA sensor to study space debris too small to be seen from Earth | Science


A fragment of space debris much smaller than a millimeter ripped a 7-millimeter-wide chip in a window of the International Space Station.


By Ilima Loomis

The movie Gravity dramatized the risks of space junk. But while flying keys and broken rockets may pose the most lethal threat to spacecraft, most orbital debris is actually much smaller, like paint chips and shattered satellites. Now, NASA hopes to learn more about the dust-sized microdeposits that orbit the Earth with the Space Debris Sensor (SDS), which will be attached to the International Space Station (ISS) after a cargo launch on December 4 by SpaceX

based on radars, the United States Air Force tracks approximately 23,000 objects larger than a baseball, so satellite operators can avoid collisions by maneuvering out of the way. But much less is known about the smallest debris, says Brian Weeden, director of program planning for the Secure World Foundation, a non-profit organization focused on space sustainability in Washington, DC. The SDS will study objects smaller than one millimeter, and at high speeds they can still cause real damage, says Weeden. "If a satellite is in orbit for 10 or 15 years, those small abrasions can have an impact by degrading sensors or degrading materials on the satellite," he says.

NASA previously studied microdebris by inspecting the windows and radiators of space shuttles, which returned to Earth with small impact marks. "A detailed ground inspection could estimate what sizes were the objects that impacted it, but there is limited information that can be obtained from that," says Joseph Hamilton, orbital debris scientist and SDS principal investigator at the Johnson Space Center in Houston, Texas.

After it is mounted on the ISS, the new sensor will offer better management of the true population of micro-debris. The 1-square-meter detector in the SDS contains layers of thin sensors embedded within a mesh of thin wires. When garbage hits the surface of the SDS, it will break a number of these wires, which correlate with the size of the particle. The damage to the layers below gives a feeling of velocities and trajectories of particles. The back plate will measure the intensity of the impact, helping scientists estimate the density of the object.

With these data, scientists can determine the orbits of particles, which provide clues to their origins. An elliptical orbit, for example, suggests that a particle is a natural micrometeoroid, while a circular orbit implies that it probably came off a satellite. And by obtaining a more accurate estimate of the microdebric population, scientists can extrapolate and better predict populations of objects larger than 1 millimeter, but less than 10 centimeters. These objects can cause more significant damage to spacecraft, but they are still too small to be tracked by radar, says Hamilton.

The SDS, which will orbit the ISS altitude of about 400 kilometers, is considered a technology demonstration. If successful, future missions could study microdebrials at altitudes in the range of 700-1000 kilometers, a more congested area of ​​space where less is known. The findings could help satellite designers to develop better protection, while improved models of the microdebric population could help them find an orbit where space dust is a minor problem.

Some companies have detected opportunities to study space junk. Astroscale, a private satellite services company headquartered in Singapore, developed a 22 kilogram microsatellite called IDEA OSG 1 that studied waste at these higher altitudes, between 600 and 800 kilometers. On November 28, it was one of the many satellites launched on a Russian Soyuz rocket that failed to reach its target orbit, and is presumed to have been lost. Prior to the launch, Astroscale's director of operations, Chris Blackerby, based in Tokyo, said the company was looking for opportunities to share data collected by the satellite through agreements with government agencies or private organizations. Astroscale did not respond to requests for comment on the failure of the Russian rocket.

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