STEREO (Solar Terrestrial Relations Observatory) is a pair of nearly identical solar probes that were launched in 2006 into different heliocentric orbits in respect to Earth. This enabled stereoscopic imaging of the Sun and solar phenomena, such as coronal mass ejections. The second probe, STEREO-B lost contact with Earth on 2016, while STEREO-A remains operational to this day (as of 2022)
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