Image Processing Reference
In-Depth Information
Figure 9.1
Example of an image of the sun's corona. This image is very clean with no CCD
speckle.
In the space environment, CCDs are bombarded by cosmic ray ions (CRs) that reg-
ister as counts in the CCD. Therefore, for space-based use, CCDs are shielded and
radiation-hardened to minimize the permanent damage. In particularly high-radia-
tion environments, radiation hits can significantly degrade the quality and useful-
ness of the data. Even for ground-based observations with long integration times,
CR hits can be problematic.
Figure 9.1 shows an example of an image taken with LASCO onboard the
SOHO. This image is very clean with no evidence of CR speckle. Conversely, the
image shown in Fig. 9.2 has suffered significant particle hits. This was caused by
high energy particles accelerating close to the sun and impacting the CCD leading
to the characteristic “snow” that in some cases almost completely whites out the im-
age. 2
The effects of this speckle noise may be significantly reduced by the applica-
tion of a correctly designed soft morphological filter.
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