The new Nature Astronomy paper The impact of satellite trails on Hubble Space Telescope observations (Kruk et al. 2023) describes an AI-based object classification method used to find satellite trails in Hubble Space Telescope images.
Hubble images with satellite trails are now in the popular news. I checked several links and this one from Gizmodo's Satellite Swarms Like SpaceX’s Starlink Are Increasingly Spoiling Hubble Telescope Images caught my eye.
A particularly bad satellite streak appears in this Hubble image. Image: NASA/ESA/S. Kruk et al., 2023
Two linear features stand out; the vertical one associated with the overexposed object looks to me to be a diffraction spike of some type, but half of the photo is overwhelmingly dominated by a huge fuzzy, diffuse bright streak crossing at an angle.
The caption labels this only as a "particularly bad satellite streak" but I don't see any other way right now than to conclude that this satellite passed so close in front of Hubble that it was out of focus!
It's not broad due to overexposure - we can confirm this by checking gray levels and by noticing we can still see stars behind it.
Question: Did this satellite streak past Hubble so close that it was out of focus? If so, just how close was it?
note: the caption for Figure 1 does call this a "broad out-of-focus trail (ja4tg4lsq)" because that's what it looks like, but without an identification of the satellite (position (within a few kilometers I suppose) and direction during the exposure time should make that fairly easy) there could be other artifact mechanisms that might be responsible.
Since Hubble's aperture dimension is known, all we need is a plate scale for this image to estimate the distance due to DOF issues.
Related, potentially helpful:
Hubble's resolution is 0.014 arc seconds (6.8e-8 radian) and its mirror diameter is 2.4 m. So objects closer than (2.4/2)/6.8e-8 m ~= 18,000 km will become detectably blurred and would benefit from refocussing.