After seventeen years, a spacecraft makes its first visit home — ScienceDaily

 The dual STEREO (Photo voltaic TErrestrial RElations Observatory) spacecraft launched on Oct. 25, 2006, from the Cape Canaveral Air Pressure Station in Florida. STEREO-A (for “Forward”) superior its lead on Earth as STEREO-B (for “Behind”) lagged behind, each charting Earth-like orbits across the Solar.

In the course of the first years after launch, the dual-spacecraft mission achieved its landmark objective: offering the primary stereoscopic, or multiple-perspective, view of our closest star. On Feb. 6, 2011, the mission achieved one other landmark: STEREO-A and -B reached a 180-degree separation of their orbits. For the primary time, humanity noticed our Solar as a whole sphere.

“Previous to that we had been ‘tethered’ to the Solar-Earth line — we solely noticed one facet of the Solar at a time,” mentioned Lika Guhathakurta, STEREO program scientist at NASA Headquarters in Washington, D.C. “STEREO broke that tether and gave us a view of the Solar as a three-dimensional object.”

The mission completed many different scientific feats over time, and researchers studied each spacecraft views till 2014, when mission management misplaced contact with STEREO-B after a deliberate reset. Nevertheless, STEREO-A continues its journey, capturing photo voltaic views unavailable from Earth.

On Aug. 12, 2023, STEREO-A’s lead on Earth has grown to 1 full revolution because the spacecraft “laps” us in our orbit across the Solar. Within the few weeks earlier than and after STEREO-A’s flyby, scientists are seizing the chance to ask questions usually past the mission’s attain.

A 3D View of the Solar

In the course of the Earth flyby, STEREO-A will as soon as once more do one thing it used to do with its twin within the early years: mix views to realize stereoscopic imaginative and prescient.

Stereoscopic imaginative and prescient permits us to extract 3D data from two-dimensional, or flat, photos. It is how two eyeballs, searching on the world from offset places, create depth notion. Your mind compares the pictures from every eye, and the slight variations between these photos reveal which objects are nearer or farther away.

STEREO-A will allow such 3D viewing by synthesizing its views with NASA’s and the European House Company’s Photo voltaic and Heliospheric Observatory (SOHO) and NASA’s Photo voltaic Dynamics Observatory (SDO). Higher but, STEREO-A’s distance from Earth adjustments all through the flyby, optimizing its stereo imaginative and prescient for various sized photo voltaic options at completely different occasions. It is as if scientists had been adjusting the deal with a a number of million-mile-wide telescope.

STEREO scientists are utilizing the chance to make much-needed measurements. They’re figuring out lively areas, the magnetically advanced areas underlying sunspots, hoping to uncover 3D details about their construction often misplaced in 2D photos. They will additionally take a look at a brand new concept that coronal loops — large arches typically seen in close-up photos of the Solar — aren’t what they seem like.

“There’s a current concept that coronal loops may simply be optical illusions,” mentioned Terry Kucera, STEREO mission scientist at NASA’s Goddard House Flight Heart in Greenbelt, Maryland. Some scientists have advised that our restricted viewing angles make them seem to have shapes they could not really have. “For those who have a look at them from a number of factors of view, that ought to change into extra obvious,” Kucera added.

Inside a Photo voltaic Eruption

It is not simply what STEREO-A will see because it flies by Earth, but in addition what it should “really feel,” that might result in main discoveries.

When a plume of photo voltaic materials often known as a coronal mass ejection, or CME, arrives at Earth, it could actually disrupt satellite tv for pc and radio alerts, and even trigger surges in our energy grids. Or, it might have hardly any impact in any respect. All of it depends upon the magnetic discipline embedded inside it, which may change dramatically within the 93 million miles between the Solar and Earth.

To grasp how a CME’s magnetic discipline evolves on the way in which to Earth, scientists construct laptop fashions of those photo voltaic eruptions, updating them with every new spacecraft remark. However a single spacecraft’s information can solely inform us a lot.

“It is just like the parable in regards to the blind males and the elephant — the one who feels the legs says ‘it is like a tree trunk,’ and the one who feels the tail says ‘it is like a snake,'” mentioned mentioned Toni Galvin, a professor on the College of New Hampshire and principal investigator for one among STEREO-A’s devices. “That is what we’re caught with proper now with CMEs, as a result of we usually solely have one or two spacecraft proper subsequent to one another measuring it.”

In the course of the months earlier than and after STEREO-A’s Earth flyby, any Earth-directed CMEs will go over STEREO-A and different near-Earth spacecraft, giving scientists much-needed multipoint measurements from inside a CME.

A Essentially Totally different Solar

STEREO-A was additionally near Earth in 2006, shortly after launch. That was throughout “photo voltaic minimal,” the low-point within the Solar’s roughly 11-year cycle of excessive and low exercise.

“The Solar was so quiet at that time! I used to be wanting again on the information and I mentioned ‘Oh yeah, I acknowledge that lively area’ — there was one, and we studied it,” Kucera mentioned, laughing. “OK, it wasn’t fairly that unhealthy — nevertheless it was shut.”

Now, as we strategy photo voltaic most predicted for 2025, the Solar is not fairly so sleepy.

“On this section of the photo voltaic cycle, STEREO-A goes to expertise a basically completely different Solar,” Guhathakurta mentioned. “There may be a lot data to be gained from that.”