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First complete image of the far side of the sun taken on June 1, 2011. Credit: NASA/STEREO

The far side unveiled! This is the first complete image of the solar far side, the half of the sun invisible from Earth. Captured on June 1, 2011, the composite image was assembled from NASA's two Solar TErrestrial RElations Observatory (STEREO) spacecraft. STEREO-Ahead's data is shown on the left half of image and STEREO-Behind's data on the right.

The STEREO spacecraft reached opposition (180° separation) on February 6 but part of the sun was inaccessible to their combined view until June 1. This image represents the first day when the entire far side could be seen.

The image is aligned so that solar north is directly up. The seam between the two images is inclined because the plane of Earth's - and STEREO's - orbit, known as the "ecliptic", is inclined with respect to the sun's axis of rotation. The data was collected by STEREO's Extreme Ultraviolet Imagers in the SECCHI instrument suites.

STEREO was built and is operated for NASA by the Applied Physical Laboratory of the Johns Hopkins University; the spacecraft were launched on October 25, 2006 aboard a Delta II. The SECCHI instrument suite is a collaboration led by the Naval Research Laboratory, and the EUVI instruments were built by the Lockheed Martin Solar and Astrophysics Laboratory.

For more about the STEREO mission visit www.nasa.gov/stereo