A new Massachusetts Institute of Technology study sheds light on the connection between space weather and satellite equipment failures, important information for scientists as they try to better engineer critical weather- and climate-watching tools before they are launched into space.
Exactly how space weather harms costly satellites is not well-understood, because if something goes wrong, researchers aren't able to retrieve the satellite from space to figure out what happened. The study attempts to pinpoint exactly when and how space weather might have caused past failures, giving engineers an idea of how to build stronger, safer satellite parts in the future.
"This research really serves as a starting ground to better understand failure mechanisms," said co-author Whitney Lohmeyer, Ph.D. candidate at MIT's Department of Aeronautics and Astronautics. "It helps us determine ways to design satellites to be more tolerant to these mechanisms."
Space weather most commonly comes from the sun, when the star produces high-speed solar winds, solar flares and coronal mass ejections -- massive eruptions of magnetized plasma and solar winds from the sun's outer atmosphere.
These phenomena interfere with the Earth's magnetic field, spurring geomagnetic storms that are thought to cause satellite components to stop working.
The MIT researchers examined a series of failures that happened on a fleet of eight commercial geostationary telecommunications satellites over 16 years, attempting to quantify the impact of space weather on the satellites.
Specifically, they looked at 26 anomalies that happened in what is called a solid-state power amplifier, an important part of satellite communication systems because it enhances signals that have become faint after traveling from Earth. (Backup amplifiers ensured that none of the anomalies caused the entire satellite to shut down.)
By comparing when the failures occurred to the space weather conditions at the time that were tracked by other satellites, including the National Oceanic and Atmospheric Administration's Geostationary Operational Environmental Satellites, the researchers tried to draw a connection between different stages of solar activity and the failures.
A solar wind stream hit Earth's magnetic field during the early hours of March 1st, 2011. The impact sparked a polar geomagnetic storm that was, at first, minor, but the storm had intensified throughout the day. Photo by NASA Goddard Photo and Video
With little data, connection between space weather and failures still fuzzy
The sun goes through what is called the solar magnetic activity cycle about every 11 years. At solar maximum, solar flares and coronal mass ejections happen more often.
But surprisingly, the researchers didn't see a clear connection between high geomagnetic activity and the anomalies.
"If you look at those anomalies ... [they] are occurring during the declining phase of the solar cycle, when geomagnetic activity is generally known to be high," Lohmeyer said, "but at the actual time of the anomalies, the geomagnetic activity is low."
Because satellite amplifiers are highly shielded, the researchers guessed that the malfunctions were not due to surface charging -- when the geomagnetic activity causes charged particles to build up on the outside of the satellite.
"This suggested that we should investigate internal charging because we thought maybe there's an accumulating effect," Lohmeyer said. "Maybe it takes time for the charge to build up to a certain level."
The results of the study suggest that space weather causes high-energy electrons to penetrate satellites' structure and accumulate over time, eventually causing a sudden electrostatic discharge that disables the amplifiers.
But despite the fact that the researchers had 16 years of data to work with, there isn't yet enough evidence to prove that accumulation of internal charging is behind the failures.
To get a clearer picture of how space weather affects satellite components, Lohmeyer said, more telecommunications companies have to provide researchers with access to data. She explained that information about satellite failures is usually kept secret so people won't think a certain company's telecommunications services are unreliable.
With this study, Inmarsat PLC, a U.K.-based telecommunications firm, became one of the first companies to collaborate with researchers, and Lohmeyer hopes this will set an important precedent for future research on space weather and satellites.
Lohmeyer also stressed that her research was not meant to show that Inmarsat's communications satellites were more prone to failures than satellites operated by other communications companies.
"Relatively speaking, the numbers are quite small," she said, "but anomalies are still occurring, so that means there are ways that we can improve design."
NOAA satellites troubled by more than space weather
Janet Green, a space weather physicist with NOAA, said the research has possible applications to her agency's GOES satellites. GOES satellites hover 22,300 miles above Earth, providing critical "big picture" data to forecasters about severe weather and other atmospheric phenomena.
"So far, for the current fleet of GOES satellites, we haven't had any permanent failures related to space weather," she said. "But that doesn't mean that we couldn't have an event that could go beyond what the design limits are and cause some problems."
Amid a challenging budget environment, the launch of a new series of NOAA geostationary satellites, GOES-R, has been pushed back to mid-2016. Ultimately, the satellites will play a major role in monitoring changing climatic conditions and severe weather, and the delay raises concerns about possible gaps in critical data (E&E Daily, Sept. 20).
But there's also good news about satellites and space weather coming from NOAA: Earlier this month, the agency announced that the Deep Space Climate Observatory satellite, or DSCOVR, is set to launch in 2015.
DSCOVR will float about 1 million miles away from the Earth, providing scientists with an early warning system for solar storms before they interfere with communications systems and satellite operations and cause other potential damage.
DSCOVR was the brainchild of climate change advocate and then-presidential candidate Al Gore, who wanted it to provide continuous footage of the Earth in addition to its other functions. But the satellite was placed in storage in 2001 when Republicans dubbed it "GoreCam" and delayed the project (Greenwire, Aug. 8, 2001).
Reprinted from ClimateWire with permission from Environment & Energy Publishing, LLC. 202-628-6500.
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