September 16, 2013
Satellites Need Better Protection From Space Weather
Lee Rannals for redOrbit.com - Your Universe Online
Scientists say space weather could be causing some satellite malfunctions due to high-energy electrons.
Space weather is a biproduct of solar activity. When an eruption takes place on the sun's surface, it ejects charged particles which sometimes head straight towards Earth. MIT researchers writing in the journal Space Weather say this phenomenon is causing some geostationary satellites to experience failures despite efforts to protect these orbiting communication tools.
Geostationary satellites orbit at the same rate as the Earth's rotation, which allows the satellites to maintain a constant location relative to the planet throughout their lifetime. Sensitive electronics aboard these satellites are covered with layers of protective shielding, but over time this armor gets beat down by radiation, degrading its components and performance.
"If we can understand how the environment affects these satellites, and we can design to improve the satellites to be more tolerant, then it would be very beneficial not just in cost, but also in efficiency," said Whitney Lohmeyer, a graduate student in MIT's Department of Aeronautics and Astronautics.
The team analyzed space weather conditions at the time of 26 failures in eight geostationary satellites over 16 years of operation. They found that most of the failures took place at times of high-energy electron activity during the declining phase of the solar cycle. The scientists believe this particle flux may have accumulated in the satellites over time, which created internal charging that damaged the amplifiers inside the orbiting objects.
Lohmeyer said that having a better understanding of how space weather affects satellites could provide a better, more prepared next generation of communications satellites. When a geostationary satellite experiences a failure, it can cause interruptions in cable television, Internet services and even global communications.
"Users are starting to demand more capabilities," Lohmeyer notes. "They want to start video-streaming data, they want to communicate faster with higher data rates. So design is changing — along with susceptibilities to space weather and radiation that didn't used to exist, but are now becoming a problem."
Engineers design geostationary satellites with space weather in mind, but it may not be enough.
"Space weather is a lot more dynamic than models predict, and there are many different ways that charged particles can wreak havoc on your satellite's electronics," Kerri Cahoy, an assistant professor of aeronautics and astronautics at MIT, said in a press release. "The hard part about satellites is that when something goes wrong, you don't get it back to do analysis and figure out what happened."
As a satellite ages, high-energy electron activity could penetrate and accumulate inside it, causing internal charging that damages amplifiers and other electronics.
"Once you get into a 15-year mission, you may run out of redundant amplifiers," Lohmeyer says. "If a company has invested over $200 million in a satellite, they need to be able to assure that it works for that period of time. We really need to improve our method of quantifying and understanding the space environment, so we can better improve design."