It’s not a huge spoiler to reveal that "Gravity" isn’t about an event-free spacewalk in the unspoiled vacuum of Earth’s low orbit.
What causes the drama is also what compels former Utah State professor Gil Moore: the clutter.
"It’s all the general question of how do you manage all of the material that’s floating around up there in space," he says.
There’s a dense web of space junk in our planet’s lower orbit — home to the International Space Station, military and GPS satellites, and debris both manmade and extraterrestrial. In the far-fetched "Gravity," the material collides in a deadly chain reaction caused by a Russian missile strike, but in the real world, U.S. Strategic Command prevents catastrophe by accurately predicting the objects’ flight paths.
Or at least, they try.
Each object is a different shape and creates a unique "drag" through the upper atmosphere, which is a vacuum by terrestrial standards but is nonetheless not-quite-empty space. Complicating matters further is that the atmospheric density can vary wildly due to solar flares and coronal mass ejections (CMEs) that occur 93 million miles away on the Sun. And that’s why Moore’s POPACS were born.
Three 10-centimeter Polar Orbiting Passive Atmospheric Calibration Spheres hitched a ride Sept. 29 aboard an unmanned Falcon 9 rocket that SpaceX launched from Vandenberg Air Force Base in California. The spheres weigh 1, 1 ½ and 2 kilograms and will orbit the Earth for 10, 12 ½ and 15 years, respectively, while students and scientists record their activity. Because they are perfectly round and lack the geometric complexities of, say, a space station, the orbs should provide simple data with which to judge the effects of a stormy Sun.
Moore isn’t the only person with Utah State ties involved in the project. Former USU master’s student David Yoel is CEO of American Aerospace Advisors, which cut and polished the spheres and filled them with bismuth shot and commemorative sand from early U.S. rocket launches. And Planetary Systems Corporation founder Walter Holemans, another USU master’s grad, built the box (or technically, "canisterized satellite dispenser") that successfully ejected the three spheres into space. He didn’t charge Moore for his previously Earthbound design — "I needed to prove that this dog could hunt."
POPACS won’t have profound meaning for communications satellites, which are farther out in what is called geosynchronous orbit, meaning they take a day to orbit the Earth. Currently POPACS are orbiting Earth every 100 minutes. But before anybody launches a low-orbit military or GPS satellite, they’ll want assurances that it’s not going up there to be destroyed when something else comes floating along.
"And floating is the wrong term," said Tremonton resident Tyler Allred, who shoots astrophotography from his backyard observatory and pitched in to separate POPACS from the rest of the junk. "Most of these things are moving really fast — many, many times faster than a bullet."
The spheres will each get as close to Earth as 316 kilometers and as far as 1,488 kilometers, eventually settling in a circular orbit of 316 kilometers and burning up. Their orbit will be roughly polarized to cause the spheres to pass through what are known as auroral zones — known to the layman for the remarkable nighttime light shows of aurora borealis and aurora australis but significant to POPACS because of their high concentration of ionized solar particles. University students — the Aggies’ Get Away Special space research team among them — and U.S. Strategic Command will track the objects and measure the effects of solar events on their orbits.
If satellites continue to populate the upper atmosphere without accurate predictors, Holemans says, the consequences may not be Hollywood-worthy, but it might lead to a "runaway problem." People in the space industry "could find ourselves out of a job," he said, barred from the void by a layer of spinning debris.
Moore enlisted NASA’s help for POPACS’ predecessor, 19-inch disco balls dubbed Project Starshine that were hauled into space on a shuttle and then tracked by children worldwide as they flashed through the night sky. This time it wasn’t so easy; Moore spent 10 years searching for a POPACS vector before he eventually reached a square deal with the private SpaceX, helmed by PayPal founder Elon Musk.
Told that the eventuality described by Holemans seems mighty dire and asked why his project wasn’t greenlighted sooner, Moore said he’s not sure.
"I’ve always asked the same question," Moore said. "‘Why isn’t everybody anxious to put up my satellites to do this work?’ It’s taken me 10 years to get these suckers up there, so all I care about is that they’re there, finally."
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