Bad space weather -- everything from solar flares, geomagnetic storms and electromagnetic radiation has wreaked havoc on a number of satellites over the years and much more needs to be done to protect these systems that provide so much of our communications systems.
Those were a couple conclusions discussed by a team of Massachusetts Institute of Technology researchers looking into the impact of space weather on satellites in a paper they published in the journal, Space Weather.
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The MIT team analyzed space weather conditions at the time of 26 failures in eight geostationary satellites between 1996 and 2012 . 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 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, the MIT researchers stated.
To undertake the study, the MIT team partnered with the London-based Inmarsat telecommunication firm to analyze some 665,000 hours of telemetry data from eight of the company's satellites, including temperature and electric-current measurements from the satellites' solid-state amplifiers. From these data, the researchers analyzed scientific space-weather data coinciding with 26 anomalies from 1996 to 2012, the majority of which were considered "hard failures" -- unrecoverable failures that may lead to a temporary shutdown of the spacecraft, MIT stated.
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Specifically, the researchers said they analyzed what's known as the Kp index, a measurement of geomagnetic activity that is represented along a scale from zero to nine. Satellite engineers incorporate the Kp index into radiation models to anticipate space conditions for a particular spacecraft's orbit. However, as the team found, most of the amplifier failures occurred during times of low geomagnetic activity, with a Kp index of three or less -- a measurement that engineers would normally consider safe. The finding suggests that the Kp index may not be the most reliable metric for radiation exposure.
The team said they found that many amplifiers broke down during times of high-energy electron activity, a phenomenon that occurs during the solar cycle, in which the Sun's activity fluctuates over an 11-year period. The flux of high-energy electrons is highest during the declining phase of the solar cycle -- a period during which most amplifier failures occurred. Over time, such high-energy electron activity may penetrate and accumulate inside a satellite, causing internal charging that damages amplifiers and other electronics. While most satellites carry back-up amplifiers, these amplifiers may also fail, MIT said.
"Once you get into a 15-year mission, you may run out of redundant amplifiers," said Whitney Lohmeyer, a graduate student in MIT's Department of Aeronautics and Astronautics in a statement. "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."
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