Aug. 11 (UPI) — On Saturday, NASA’s STEREO-A spacecraft will pass between the Earth and the sun for the first time since it was launched 17 years ago.
The Solar Terrestrial Relations Observatory spacecraft was launched in 2006, along with a sister satellite called STEREO-B, with the goal of creating three dimensional images of the sun.
The two satellites were able to create the first stereoscopic view of the sun while following an orbit around the sun that was similar to the Earth’s orbital path.
By 2011, “STEREO-A and -B reached a 180-degree separation in their orbits. For the first time, humanity saw our Sun as a complete sphere.”
That was important, NASA STEREO program scientist Lika Guhathakurta said, because “prior to that we were ‘tethered’ to the sun-Earth line — we only saw one side of the sun at a time,” and that “STEREO broke that tether and gave us a view of the sun as a three-dimensional object.”
In 2014, NASA lost contact with the STEREO-B spacecraft but STEREO-A continued its mission.
NASA hopes to use STEREO-A’s closer proximity to the Earth to help create detailed three-dimensional images of the sun by synthesizing with observations from NASA’s Solar Dynamics Observatory and the European Space Agency’s Solar and Heliospheric Observatory.
“STEREO-A’s distance from Earth changes throughout the flyby, optimizing its stereo vision of different sized solar features at different times, it’s as if scientists were adjusting the focus on a several million-mile-wide telescope,” NASA said.
NASA hopes the flyby will offer insight into a phenomenon known as “coronal loops,” arch-like structures that are made up of plasma and appear in the sun’s atmosphere.
Some scientists have proposed a theory that coronal loops are optical illusions created by observing the sun from a single perspective.
“If you look at them from multiple points of view, that should become more apparent,” said NASA STERO project scientist Terry Kucera.
Scientists also hope that potential interference to STEREO-A’s instruments could shed light on coronal mass ejections, when plasma and magnetic fields shoot off of the sun.
