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Will be interesting to see what they use for a receiving antenna. 90 dBi gain is about the limit for single aperture reflector antennas at RF, as you contended

Will be interesting to see what they use for a receiving antenna. 90 dBi gain is about the limit for single aperture reflector antennas at RF, as you contended with structure deformation at low frequencies, then surface roughness at high frequencies, not to mention tracking a fast moving object with that precision to keep it in the beam width. At X-rays, I don’t know how you would focus it as the roughness is in on a molecular scale. So going to higher frequencies has its limits. I don’t know what the equivalent gain of these large, optical telescopes are, but they seem to suffer from the same problems. The plasma penetration must the the real objective. You can get thru the plasma with standard RF, it just takes lots more power, or lower data rate, but a low reset beacon is feasible, just not voice comms.

jbay808 7y ago
Even to x-rays, smooth surfaces become reflective at grazing incidence, so you can make mirrors that are constructed on that principle. Not simple to do, but not impossible either.
- madengr 7y ago
  The gain falls off as the RMS surface roughness becomes a fraction of a wavelength; see figure 1 here: https://arxiv.org/pdf/1007.4600.pdf https://arxiv.org/pdf/1007.4600.pdf So it would be interesting to see how that effects it. I suppose a crystal fractured along the lattice for an atomically smooth surface.
xioxox 7y ago
In X-ray astronomy we often use Wolter Type 1 optics based on grazing incidence. These can be made with various techniques depending on the spatial accuracy (point spread function) required, e.g. foils for low accuracy or even stacked silicon wafers planned for the Athena telescope. The effective area of the telescope is smaller than the physical mirror size as everything has to be reflected at grazing incidence. We often use CCDs to detect the X-rays.

jbay808 7y ago

Even to x-rays, smooth surfaces become reflective at grazing incidence, so you can make mirrors that are constructed on that principle. Not simple to do, but not impossible either.

madengr 7y ago
The gain falls off as the RMS surface roughness becomes a fraction of a wavelength; see figure 1 here: https://arxiv.org/pdf/1007.4600.pdf https://arxiv.org/pdf/1007.4600.pdf So it would be interesting to see how that effects it. I suppose a crystal fractured along the lattice for an atomically smooth surface.

xioxox 7y ago

In X-ray astronomy we often use Wolter Type 1 optics based on grazing incidence. These can be made with various techniques depending on the spatial accuracy (point spread function) required, e.g. foils for low accuracy or even stacked silicon wafers planned for the Athena telescope. The effective area of the telescope is smaller than the physical mirror size as everything has to be reflected at grazing incidence. We often use CCDs to detect the X-rays.