Important notice about STEREO Behind
Welcome to the STEREO Learning Center
Image artifacts - Cosmic rays
Cosmic rays and solar energetic particles are highly energetic particles that
travel through space. Some of these originate from the Sun. Others, known as
galactic cosmic rays, come from outside the solar system. When they pass
through the detectors, they produce thin bright spots or streaks.
|Close up of cosmic ray track seen on the STEREO Behind COR2
The high compression factors used for the temporary
images can cause cosmic ray events to be significantly distorted, as shown in
the sample images below. Even the full resolution data have some compression
applied to them, resulting in a small amount of distortion of the brightest
|Two cosmic rays distorted by the high compression factors
applied to beacon data, as seen by the STEREO Behind EUVI telescope on
January 18, 2010
||Same cosmic rays as seen in the full resolution data. Many
more cosmic ray events are visible. Only the brightest two show up in
the beacon image.
On July 19, 2011, the software for generating the browse images was changed to
not apply smoothing when making JPEG images that are larger in size than the
original data. The smoothing, as seen in the left image above, was found to
contribute to making the cosmic ray features look like artificial structures.
The unsmoothed images, although not quite as pleasing looking, are more
representative of the actual data.
Back to image artifacts page.
Last Revised: Wednesday, 20-Jul-2011 13:34:54 EDT
Responsible NASA Official:
Webmaster: Kevin Addison