Telescopes are incredible. You can stand on your porch and, like Galileo, view the major moons of Jupiter. On a much grander scale, if you put a really big telescope in orbit, you can see billions of years back in time.
But telescopes, as classically conceived, are cyclopean—with just one eye, you get only a flat view of the world. You need two eyes on the sky if you want to add some depth to your field of view, and for stereoscopic views of our own star, you need two satellites in solar orbit. A Solar Terrestrial Relations Observatory, or STEREO, in fact.
NASA launched the two spacecraft that comprise the STEREO mission on Oct. 25, 2006, and as of last fall, they have now spent 10 years studying solar weather, the charged particles emitted from our star that can affect us on Earth, from the Northern Lights to power outages (see: 1989, Quebec). With STEREO-A (“Ahead”) orbiting the sun on a tighter, faster orbit than Earth and STEREO-B (“Behind”) in a wider, slower orbit than Earth, the mission has a unique set of viewpoints and a situational advantage over other solar observation spacecraft, which orbit at the centerline between the sun and Earth.
In honor of STEREO’s decade in space, NASA released the above video, narrated by STEREO Deputy Project Scientist Terry Kucera, highlighting the mission’s top discoveries. Using multiple instruments, STEREO has studied the interaction of the solar wind with the tails of comets, the structure and dynamics of storms in the solar wind known as coronal mass ejections and, crucially, given NASA an eye on the far side of the sun from Earth to observe these storms. In monitoring our local star, two are definitely better than one.