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Comment by bobmoretti | Hacker News Reader

No matter what you do, you still have to deal with diffraction [1], which means the resolution is inversely proportional to the aperture. I think the Trump/Iran release was estimated to be pretty close to the diffraction limit.

[1] https://en.wikipedia.org/wiki/Angular_resolution#Explanation

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Just took a radars course and we definitely spent a whole section on just atmospheric effects / defraction. My only guess about how you could maybe lower the error is by monitoring and measuring the condition of the atmophere and building a model that can use that data to apply corrections and reduce error to your image.

If there was a known object in an image could a high resolution image of the known object be used to compensate for atmospheric diffraction effects?

One example is a laser guide star: https://en.m.wikipedia.org/wiki/Laser_guide_star

Yes. Ssshhh.

As I mentioned above, there is a technique called lucky imaging, where you take lots of short exposures and only use the best ones. In astronomy, this can be used to reach the diffraction limit. You need a bright source, however, and it provides a narrow field of view.

Another technique is to use multiple camera sources spread out over an area. The angle between the cameras is known, so differences in the images caused by diffraction and atmospheric aberrations can be computed out to some degree.

Yep.

  angle = k (wavelength / diameter)

And the diameter is going to be limited by the launch vehicle. But multiple satellites could improve this.

Can multi-camera/multi-view photogrammetry defeat this limit and create super-resolution imagery?

How about optical interferometry? IIRC, this can beat the diffraction limit.

Optical interferometry means you have a wider telescope. Same limit formula.

Yes, but the aperture of the interferometer is no longer limited in the same way, so we could say that interferometry gets around the “naive” diffraction limit.

Well, but if you have a bunch of these in orbit, able to image the same site, at the same time...

Can you expand on "the Trump/Iran release was estimated to be pretty close to the diffraction limit"? What is this in reference to?

https://mobile.twitter.com/realDonaldTrump/status/1167493371...

https://www.npr.org/2019/08/30/755994591/president-trump-twe...

I think your question was misunderstood, as the other replies do not go into any details on diffraction limit at all.

I too would be interested in knowing if this image is showing all we got, or because someone else looked at it and said "sure you can release it, we've got better than that anyway."

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