Are these photographic artifacts of some kind and if so how would they occur? They are almost the same exact shape and size. It is a photo of the Kuiper Belt from the New Horizon space probe taken directly from NASA web site. If it is not a common photographic event then what could it be?
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$\begingroup$ They’re present only next to bright stars, so I would suppose it has something to do with imaging captor “bleed” of the light to neighbouring pixels… $\endgroup$– Pierre PaquetteJul 11 at 17:56
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1$\begingroup$ Looks like maybe the CCD is being read-out raster wise and the pixels following saturated pixels can't be read correctly. Looks like some of the less-saturated pixels have the same effect, but shorter. Also probably a lot of data compression going on with images from New Horizons. $\endgroup$– antlersoftJul 11 at 18:03
1 Answer
Weaver et al. 2020 discusses New Horizons LORRI instrument performance in detail. The introduction says:
The LORRI CCD incorporates anti-blooming technology to eliminate bleeding of the electrons along columns when bright targets saturate (i.e., when the signal in a pixel exceeds the full-well capacity of ∼80,000 electrons).
Otherwise the tails of bright stars would be white and blocky. Figure 5, another deep image of a star field, explains similar artifacts:
The brightest stars are saturated and have black tails due to amplifier undershoot.
Jenkins et al. 2010, section 2, addressed a similar issue for the Kepler mission:
The analog electronics chain exhibits memory, necessitating the application of a digital filter to remove this effect, called Local Detector Electronics (LDE) undershoot.