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IOWA CITY -- Late last month, a NASA sounding rocket carrying a University of Iowa instrument – along with others – made an evening foray nearly 100 miles straight up into the Earth’s ionosphere, captured a trove of data and then splashed into the Atlantic Ocean all within about 10 minutes.
The mission of VIPER, standing for VLF trans-Ionospheric Propagation Experiment Rocket, was to investigate hard-to-study radio waves that escape through Earth’s ionosphere – an expanse stretching 50 to 400 miles above Earth, forming the boundary between where humans live and outer space.
If successful, scientists will achieve a better understanding of the “basic science” impacting the environment surrounding GPS and geosynchronous satellites – like those used for weather monitoring and communications.
“We're just trying to do some basic physics to understand how waves propagate through the ionosphere,” said UI research scientist and engineer George Hospodarsky, who led the UI contribution to the project. “That’s a region of the Earth's atmosphere that’s hard to measure because planes can't get high enough … and satellites can't get low enough.”
At NASA’s Wallops Flight Facility along the coast of Virginia, just south of its border with Maryland, a sounding rocket carrying the VIPER successfully launched at 9:15 p.m. May 26 – descending only minutes later and disappearing into the Atlantic Ocean.
Hospodarsky told The Gazette preliminary data seems promising. “It looks interesting,” he said. “But it's going to take a lot more analysis to really understand it all.”
For the mission, Hospodarsky and fellow UI researchers designed and built a key component of a magnetic field instrument on the rocket – its “search coil magnetometer,” used to study the magnetic component of low-frequency electromagnetic waves in space.
The project’s principal investigator is John Bonnell, a research physicist with the University of California-Berkeley. Other collaborators came from University of Colorado-Boulder, for example, and the mission involved ground-based systems in Maine, North Carolina, Georgia, Colorado, and Virginia.
The late-night timing of the launch was key because the very low-frequency radio waves the project aimed to study, which are produced by both natural and artificial means, remain trapped in the ionosphere during the day.
But at night, some escape and accelerate electrons in the Van Allen Radiation Belts – discovered by famed UI Professor James Van Allen in 1958, described as “a doughnut-shaped region of charged particle radiation trapped by the Earth’s magnetic field.”
“Those belts of intense energetic electron fluxes cover a range of distances from the Earth, from as close as 14,300 miles altitude out to 23,500 miles altitude,” Bonnell said in a NASA news release. “So, satellites in those orbits are often engulfed by the Van Allen Radiation Belts and have to tolerate the effects those energetic particles have on electronics and materials.”
Not only will this novel data set bolster basic science researchers attempted to investigate in the 1960s, it will enable confirmation and comparison with existing computer models of how waves propagate through the ionosphere.
“People now have computer models to try to simulate what they think happens when the waves propagate through the ionosphere,” Hospodarsky said. "Of course, those are computer models. Unless you have measurements, you don't really know -- is it giving you the right answer?“
Once scientists have the right answer, they can then ask another question -- can they manipulate the radiation belt in some way?
“Scientists have proposed that we may be able to mitigate the radiation belt -- by putting transmitters into space we could actually make the radiation belts weaker,” Hospodarsky said. “There have been some proposals by scientists, and I don't know how likely you could actually pull it off, but could we actually put transmitters up, or even put transmitters on the ground with this new theory, and ... make the radiation belts weaker and help protect the satellites.”
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