February 27, 2013
Researcher Says Space Dust Culprit Behind Falling Satellites
Lee Rannals for redOrbit.com - Your Universe Online
According to an aeronautics and astronautics professor at Stanford University, "space dust" is the likely culprit behind why satellites fail.Satellites are threatened by both asteroids and "space junk," which are particles of man-made debris that orbit Earth. However, the threat from these impacts is actually relatively low, and most satellites that have died in space were knocked out by something entirely different.
Space dust, also known as cosmic dust, is a general term for debris up to 0.003-inch in size, or as small as a few molecules. Space dust can come from comets, asteroids, the Kuiper belt and asteroid impacts.
Cosmic dust is too small to cause direct harm to satellites, yet Stanford researcher Sigrid Close believes that it is nonetheless a likely accomplice in satellite failures. She says that when these tiny, rapidly traveling particles collide with an object, they turn into a quasi-neutral gas of ions and electrons known as plasma. According to Close, this plasma can create a radio signal that damages or even completely shuts down satellites.
This electromagnetic pulse (EMP) is similar to what is generated by nuclear detonations. For example, the Chelyabinsk meteoroid that exploded in the sky over Russia on February 15 created a massive EMP that knocked out cell phones towers across the region.
"Spacecraft transmit a radio signal, so they can receive one that might potentially disable them," Close explained. "So our question was: Do these plasmas emit radio signals, and if so, at what frequencies and with what power?"
To test her theory, Close performed experiments at the Max Planck Institute for Nuclear Physics in Germany. Sigrid and her colleagues fired off tiny dust particles at targets that resembled satellites at speeds of 37 miles 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.
She believes plasma that results from space dust collisions could help to explain mysteries like the European Space Agency's loss of its Olympus communication satellite in 1993. This Ka band satellite had an operating life of seven years but lasted just four of those years.
"Olympus failed during the peak of a meteor shower, but they never detected a momentum transfer, which means whatever hit it wasn't big enough to be detected mechanically," she explained. "And yet this multimillion-dollar spacecraft was effectively taken out."
Close believes that her experiments could eventually lead to a breed of satellites that are able to withstand the plasma created from space dust impacts.
"Spacecraft are being hit all the time by these particles," said Close. "So we feel like we found a smoking gun here in the sense of explaining why this doesn't always happen. And once we know what's going on, there are solutions we could implement to save billions and billions of dollars."
Sigrid is working with James Smith and Henry Garrett of NASA's Jet Propulsion Laboratory to design an experiment that could be anchored to the International Space Station to test her hypothesis.
Last year, researchers analyzing particles recovered by the Japanese asteroid probe Hayabusa found that space dust could be giving asteroids their shape.
“Our findings show the landscape itself of the very surface of an asteroid,” said Eizo Nakamura, who worked on the Hayabusa study with colleagues at Okayama University in Tsushimanaka, Japan. “An asteroidal surface is not a quiet place, but is heavy with bombardment.”
After analysis, the team found evidence of hundreds of collisions with space dust, indicating that nanoparticles were traveling at tens of thousands of miles per second. The impacts at this speed changed the chemical properties of the asteroidal surface, producing enough heat for localized melting.