Making sure a critical sensor that will fly aboard NASA’s $1.5 billion Parker Solar Probe will work properly when the spacecraft is being blasted by fierce light and radiation a scant 6.2 million kilometres (3.9 million miles) from the Sun is no small task.
But researchers at the University of Michigan who manage the spacecraft’s Solar Wind Electrons Alphas and Protons investigation – SWEAP – came up with a novel solution. They bought four vintage IMAX movie projectors on eBay for a few thousand dollars each that could be rigged to simulate the expected heat at close range to Earth’s star.
The SWEAP sensor, known as a Faraday cup, was mounted in a vacuum chamber at the Smithsonian Astrophysical Observatory in Cambridge, Mass., that was pumped down to one-billionth of an atmosphere. The light from the four projectors was directed into the chamber and onto the Faraday cup.
“It turns out a movie theatre bulb on an IMAX projector runs at about the same 5,700 degrees Kelvin, the same effective temperature as the surface of the Sun,” Justin Kasper, the instrument’s principal investigator at the University of Michigan, said in a release. “And it gives off nearly the same spectrum of light as the surface.”
The IMAX projectors provided the blazing heat and light while an ion gun was used to beam electrically charged particles into the chamber to simulate the solar wind. And the instrument worked as expected, a final hurdle on the way to launch July 31.
“Watching the instrument track the signal from the ion beam as if it was plasma flowing from the Sun was a thrilling preview of what we will see with Parker Solar Probe,” Kasper said.
Once launched, the Parker Solar Probe will execute seven flybys of Venus over nearly seven years to reach its intended elliptical orbit well inside that of Mercury. Operating behind a 4.5-inch-thick carbon composite shield, the spacecraft’s four instruments will study the plasma environment around the Sun, electric and magnetic fields and the charged particles streaming away in the solar wind.
Major objectives of the mission are to help scientists understand the mechanisms responsible for heating the Sun’s corona to million-degree temperatures and how the solar wind and charged particles are accelerated.
A better understanding of those processes should help researchers improve solar weather forecasting in the wake of coronal mass ejections and other phenomena that can adversely affect satellites, GPS and radio communications and, in some cases, disrupt power grids.