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I was looking at the Galleries in the NASA Scientific Visualization Studio and in the banner they show an image from SDO - the Solar Dynamics Observatory. I've posted it below along with a cropped, reversed tone of the green channel.

I see these "echoes" - really just periodic tire-tread-like little blip-artifacts (blipifacts) from time to time when there are certain bright events. They do seem to have a roughly cartesian distribution, spreading out away from the bright spot along all four diagonals. The vertical "spike" suggests the CCD axis is aligned to (x, y), so maybe it is vane-related? Does the instrument have a secondary supported by vanes?

What are they?

UPDATE: I found a photomontage of a bright event shown with six different wavelength bands. It's the Cinco de Mayo Flare of May 5, 2015. Many show the same effect, but different wavelengths have different patterns - strongly suggesting this is interference or diffraction, not electronic. There is always a short-period "tire-tread" combined with a long period envelope - maybe a dozen blips, then nothing, then a dozen blips... It reminds me of the diffraction pattern from a square array of points.

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Image: svs.gsfc.nasa.gov/vis/a010000/a010900/a010925/SDO_2012-03-07_171_X5Flare-Closeup.00369

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Image: The "Cinco de Mayo Flare" 05-05-2015: www.nasa.gov/feature/goddard/nasas-sdo-observes-cinco-de-mayo-solar-flare

HMI Continumum | 171Å upper transiti | 304Å Chromosph | 193Å Corona/Flare | 131Å Flaring reg.

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You can use this guide to compare the artificial color-coding to get the actual UV wavelength for each image. From here.

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  • $\begingroup$ Someone mabye could explain this image, but i am supposing that one possible reason could be a camera effect something that has to do with resolution of the image since the distance where is taken is far. The camera used for this image it may be high quality and high technology but photographing the sun compared to the planets, could be different situation since here we have to do with different intensities of solar rays which are constantly changing. Mabye this could cause this optical effects. $\endgroup$
    – Mark777
    May 22, 2016 at 11:53
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    $\begingroup$ Looks like normal diffraction in the lens of the camera. See "diffraction grating" and "airy discs". Here it is more pronounced than in a regular image as these are monochromatic. The "grouping" you notice might be due to an overlay of two different interference patterns. $\endgroup$
    – asdfex
    May 23, 2016 at 11:47
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    $\begingroup$ According to this paper they are diffraction patterns caused by a wire mesh that supports the filters. $\endgroup$
    – 2012rcampion
    May 23, 2016 at 13:48
  • $\begingroup$ Read this under "Saturation trail". They seem to be quite common with CCDs. $\endgroup$
    – Andy
    May 23, 2016 at 14:43

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2012rcampion found a nice paper detailing all the visual effects caused by the optical system of the satellite. According to the paper, the many small artifacts are caused by diffraction:

The optical setup of each AIA telescope is characterized by structures with uniform wire meshes used to support the thin filters that create the EUV passbands. The interaction between the incoming EUV radiation and the grids generates a diffraction effect.

This is the same optical effect that produces e.g. the shiny colors you see on the bottom side of a CD or any other microscopic and regular structure.

The banding of this pattern, i.e. groups of higher and lower intensity of these artifacts is not mentioned in the paper, but I suspect these to be an overlaying diffraction pattern caused by the aperture of the lens system (see "airy discs").

The vertical band is, as you wrote, a blooming effect commonly seen on all CCD-based photo sensors and caused by their specific electrical structure.

As the paper describes, these artifacts are not only an error in the final image, but can actually be used to increase the quality of the data. In your example images it is clearly visible that the most central regions are so bright that the camera sensor is saturating and not able to show any detailed structures. The diffraction patterns, on the other hand, are more or less precise copies of this region, but at lower intensity. Hence, they can be used to reconstruct the missing information in the central region. The paper shows some examples of this process, including some of the math involved to re-calculate the original image.

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  • $\begingroup$ Oh, this is really great stuff! I didn't think about it, but sure - EUV photolithography uses almost exclusively reflective optics - multilayer mirrors, since nothing more than a few microns thick will allow transmission. So these multilayer filters must be suspended by grids. The inverse diffraction method (trick) to recover more information is pretty cool - a moveable neutral density filter would be better - but not practical or reliable enough maybe for a spacecraft. Thank you very much for this! It's been bugging me for years - I thought I was the only person who saw it :) $\endgroup$
    – uhoh
    May 23, 2016 at 16:18
  • $\begingroup$ @2012rcampion Thank you also for tracking this down - the paper is great! $\endgroup$
    – uhoh
    May 23, 2016 at 16:19

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