Solar Eclipse, Scientific Opportunity
Engineering team will measure effects on GPS; ultimate goal is citizen science
During the solar eclipse on August 21, the moon will completely block the sun’s energy from reaching Earth within a 60-mile shadow that will sweep across the US, presenting scientists with a unique research opportunity. Photo courtesy of NASA.
On August 21, 2017, the US will play host to a rare natural phenomenon: a complete solar eclipse that will cut a swath from Oregon to South Carolina. And as people across the country clamor outside, eclipse glasses in hand, to see the remarkable sight of the moon blocking the sun, Joshua Semeter and his research team will be busy using GPS sensors to gather data on the Earth’s upper atmosphere.
Semeter, a Boston University College of Engineering professor of electrical and computer engineering, and his team will scatter inexpensive GPS sensors in the path of the eclipse to take measurements as it moves overhead. If all goes as planned, the project will not only deepen our understanding of Earth’s upper atmosphere—which has the potential to disrupt technology like GPS navigation systems—but will also demonstrate how cheap GPS sensors like the ones in smartphones could be used for broader “citizen science” initiatives.
During the total solar eclipse, the Moon will turn off the ionosphere’s source of extreme ultraviolet radiation: The ionosphere will go from daytime conditions to nighttime conditions. Image courtesy of NASA’s Goddard Space Flight Center/Katy Mersmann.
During a total solar eclipse, the moon is perfectly aligned between the Earth and the sun, blocking the sun’s energy from reaching the Earth within a large shadow that moves across the Earth’s surface. On August 21, this eclipse shadow, which Semeter calls a “supersonic sun shade,” will be 70 miles across and sweep across the US at between 1,500 and 3,000 miles per hour, taking about 90 minutes to travel from coast to coast. People directly under the eclipse path will have the eerie experience of watching the sun seemingly disappear during broad daylight, while those further from the path will see the sun partially covered.
But this total solar eclipse is more than a rare natural phenomenon: for scientists, it is a unique research opportunity. “It’s like a controlled experiment,” Semeter explains. “Mother Nature is providing us a nice experimental environment.”
Semeter studies the ionosphere, a layer of charged particles (electrons and ions) between 30 and 600 miles above the Earth’s surface. The ionosphere is formed when ultraviolet radiation from the sun hits the Earth’s upper atmosphere, knocking electrons free from their parent atoms. This layer is a tricky challenge for GPS navigation systems: it slows down and bends radio waves passing through it, forcing GPS devices to correct for it. The size of the correction depends on the density of charged particles, or plasma, that the radio waves travel through on their way from satellite to GPS receiver.
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