2 ms·

There's a hard physical limit (the Rayleigh criterion) on the resolution of an optical system by how big the open end is. You won't get "super zoom" capabilitie

There's a hard physical limit (the Rayleigh criterion) on the resolution of an optical system by how big the open end is. You won't get "super zoom" capabilities without a satellite the size of a stadium. https://en.wikipedia.org/wiki/KH-11_KENNEN#Resolution_and_ground_sample_distance https://en.wikipedia.org/wiki/KH-11_KENNEN#Resolution_and_gr...

alganet 2y ago
What about multiple satellites working to get one image? Like the arrays we have on Earth pointing to space, but instead, arrays on space pointing to Earth. I know there probably isn't that many KH-style satellites to do it, but would it be possible?
- GlenTheMachine 2y ago
  The alignment has to be better than half a wavelength. That's doable for RF, but for optical telescopes you're talking nanometers. That's not possible (currently or in the foreseeable future) for a spacecraft constellation.
  - sbierwagen 2y ago
    Amusingly enough, there's been some groundwork laid here by gravity wave interferometer constellations: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant... You could imagine a deep-infrared mission (longer wavelength, to soften the alignment requirements) launched into deep space (Jupiter+) where both the solar wind density is lower (reducing space weather perturbations) and reduced solar flux would reduce heat loads on the structure, (objects in Jupiter orbit get 3.6% as much light as in Earth orbits) making cooling easier. An interferometer design would also improve resolution. A not-widely advertised feature of the JWST is that, due to the same Rayleigh limits, its far infrared modes have dramatically lower resolution than its near infrared camera. A problem with a 6 meter mirror, less of a problem with a kilometer mirror.
  - wuming2 2y ago
    I remembered European Southern Observatory employing optical interferometry on the ground. And indeed it does: https://www.eso.org/public/news/eso1905/ https://www.eso.org/public/news/eso1905/
wkat4242 2y ago
Cool to see Clifford Stoll mentioned there, he was also the one detecting one of the first international state-sponsored hacking attacks on the US and wrote a book about it, The Cuckoo's Egg.

alganet 2y ago

What about multiple satellites working to get one image? Like the arrays we have on Earth pointing to space, but instead, arrays on space pointing to Earth. I know there probably isn't that many KH-style satellites to do it, but would it be possible?

GlenTheMachine 2y ago
The alignment has to be better than half a wavelength. That's doable for RF, but for optical telescopes you're talking nanometers. That's not possible (currently or in the foreseeable future) for a spacecraft constellation.
- sbierwagen 2y ago
  Amusingly enough, there's been some groundwork laid here by gravity wave interferometer constellations: https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Antenna https://en.wikipedia.org/wiki/Laser_Interferometer_Space_Ant... You could imagine a deep-infrared mission (longer wavelength, to soften the alignment requirements) launched into deep space (Jupiter+) where both the solar wind density is lower (reducing space weather perturbations) and reduced solar flux would reduce heat loads on the structure, (objects in Jupiter orbit get 3.6% as much light as in Earth orbits) making cooling easier. An interferometer design would also improve resolution. A not-widely advertised feature of the JWST is that, due to the same Rayleigh limits, its far infrared modes have dramatically lower resolution than its near infrared camera. A problem with a 6 meter mirror, less of a problem with a kilometer mirror.
- wuming2 2y ago
  I remembered European Southern Observatory employing optical interferometry on the ground. And indeed it does: https://www.eso.org/public/news/eso1905/ https://www.eso.org/public/news/eso1905/

wkat4242 2y ago

Cool to see Clifford Stoll mentioned there, he was also the one detecting one of the first international state-sponsored hacking attacks on the US and wrote a book about it, The Cuckoo's Egg.