Aeronautics and astronautics Assistant Professor Sigrid Close.
Credit: Norbert von der Groeben / Courtesy of Stanford University)


Scientist closes in on a mystery that impedes space exploration

February 27, 2013 by Simon Firth

(—New research by Stanford aeronautics and astronautics Assistant Professor Sigrid Close suggests she’s on track to solve a mystery that has long bedeviled space exploration: Why do satellites fail?

In the popular imagination, satellites are imperiled by impacts from “space junk” – particles of man-made debris the size of a pea (or greater) that litter the Earth’s upper atmosphere – or by large meteoroids like the one that recently exploded spectacularly over Chelyabinsk, Russia.

Although such impacts are a serious concern, most satellites that have died in space haven’t been knocked out by them. Something else has killed them.

The likely culprit, it turns out, is material so tiny its nickname is “space dust.”

These natural micro-meteoroids are not directly causing satellites harm. When they hit an object in space, however, they are traveling so fast that they turn into a quasi-neutral gas of ions and electrons known as plasma. That plasma, Close theorizes, has the potential to create a radio signal that can damage, and even completely shut down, the satellites they hit.

The signal is an electromagnetic pulse, or EMP – similar in concept but not in size to what is generated by nuclear detonations. (Tellingly, a massive EMP knocked out cell phones when the Chelyabinsk meteoroid hit.)

“Spacecraft transmit a radio signal, so they can receive one that might potentially disable them,” Close said. “So our question was: Do these plasmas emit radio signals, and if so, at what frequencies and with what power?”

Now, through experiments she’s led at the Max Planck Institute for Nuclear Physics in Germany, Close has proof that particles that mimic space dust can indeed cause trouble.

The researchers fired tiny dust particles at targets resembling satellites at speeds of 60 kilometers per second. “We found that when these particles hit, they create a plasma or quasi-neutral gas of ions and electrons, and that plasma can then emit in the radio frequency range,” Close said.

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