Two Satellites Have Spent 10 Years Staring at the Sun

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Two Satellites Have Spent 10 Years Staring at the Sun

STEREO A and B have been vital in helping us understand our Sun, and now the mission celebrates its 10th birthday.


On October 25, 2006—ten years ago—NASA strapped two satellites onto a Delta II rocket and sent them skyward with an important mission—to figure out what our Sun is all about.

Given that it’s the brightest object in our solar system and the big ball of fire that keeps us alive, you’d think humans would know all kinds of stuff about or friend, Sol. But, of course, for most of human history we’ve been staring at the Sun from one vantage point, and that’s the soil beneath our feet. For the past decade, though, two satellites named STEREO-A and STEREO-B, part of the Solar Terrestrial Relations Observatory mission, have been traveling ahead and behind Earth’s orbit to get a more complete picture of our sun than ever before.

The results have been stunning. Here’s a brief history of STEREO and its many, many accomplishments.

STEREO B, In The Beginning

Although other missions, like ESA and NASA’s SOHO satellite, have traversed space in search of answers to our Sun-related questions, the primary goal of STEREO was to capture the first fully 3D image of our Sun, a simultaneous rendering of our life-giving star, as well mapping coronal mass ejections (CMEs) more accurately. To achieve that feat, NASA needed to coordinate the orbits of two separate satellites, one just inside and one just outside of Earth’s own orbit, to get data from three distinct areas in our solar system.

In this image, we see nearly completed Stereo B, the satellite destined to travel behind Earth’s orbit, at NASA’s Applied Physics Laboratory in Maryland in 2005. These satellites come with an extreme ultraviolet imager, two white-light coronagraphs, and a heliospheric imager—all for studying the evolution of  CMEs  as they travel from the Sun through its atmosphere (the corona).

STEREO Is Ready For Launch

This one-minute clip shows the Delta II launch from Cape Canaveral on October 25, 2006.

After the launch, scientists hailed the satellites as ushering “a new dawn for solar observation,” with plans to also accurately measure and predict solar storms. The correct prediction of these storms could help protect future astronauts from radiation when humans finally make that long, perilous trek to Mars.

Getting Into Orbit

This is an extended animation of what STEREO’s completed and planned orbit is until late 2019. By now, STEREO-A and -B have flown by each other on the other side of the Sun and are now on their return journey to Earth. You can see the satellite’s current positions right here.

This stereoscopic image of the sun, captured in April 2007, recreates what it would be like for two human eyes to stare at the Sun (albeit on a galactic scale). This data was captured during the early portion of STEREO’s mission as its twin satellites were still near Earth.

The Sun Now Comes in 3D

 This “Eye of Sauron”-like image is the exact moment when in 2011 STEREO-A and B were in the exact position to completely capture the Sun in nearly real-time. This is the first time scientists had ever seen the Sun all at once.

Strangely, it was the first time we could say without a doubt that the Sun was indeed a sphere (though we had a good idea that was the case already.)


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