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Image artifacts - Debris

Occasionally one will see bright blobs or streaks appearing in the STEREO coronagraph images. These have been seen before by the SOHO mission, and are caused by micrometeorite impacts knocking off small pieces of the multi-layer insulation blankets which are wrapped around the spacecraft. These small debris particles are brightly illuminated by the Sun, and are easily seen by the coronagraphs if they wander into the field of view. They are tremendously out-of-focus, and often appear as "donut" shapes in the COR1 and COR2 telescopes because of the central occulter in these telescopes. The bigger the piece of debris appears, the closer it is to the telescope. Because the COR1 and COR2 images are generally built up from a series of images, the same piece of debris will often show up multiple times.

Debris event observed by the STEREO Ahead COR1 telescope on December 23, 2008		Same event as seen in COR2
Same event as seen in HI1		Same event as seen in HI2

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