空间气象可能造成卫星运行故障

Is your cable television on the fritz（发生故障）? One explanation, scientists suspect, may be the weather -- the weather in space, that is. MIT researchers are investigating the effects of space weather -- such as solar flares, geomagnetic storms and other forms of electromagnetic radiation -- on geostationary satellites（地球同步卫星）, which provide much of the world's access to cable television, Internet services and global communications.

Geostationary satellites orbit at the same rate as the Earth's rotation, essentially remaining above the same location throughout their lifetimes. These satellites are designed to last up to 15 years, during which time they may be bombarded（轰炸） by charged particles. Most satellites cover sensitive electronics with layers of protective shielding, but over time, radiation can penetrate and degrade a satellite's 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," says Whitney Lohmeyer, a graduate student in MIT's Department of Aeronautics and Astronautics.

Lohmeyer is working with Kerri Cahoy, an assistant professor of aeronautics and astronautics, to understand how sensitive components are to the weather conditions in space, and how space weather may contribute to failures.

In a paper published in the journal Space Weather, the team analyzed space weather conditions at the time of 26 failures in eight geostationary satellites over 16 years of operation. The researchers found that most of the failures occurred at times of high-energy electron activity during declining phases of the solar cycle. This particle flux, the scientists theorize, may have accumulated in the satellites over time, creating internal charging that damaged their amplifiers -- key components responsible for strengthening and relaying a signal back to Earth.

Lohmeyer says a better understanding of space weather's effects on satellites is needed not just for current fleets, but also for the next generation of communications satellites.

"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."