4 ms·

For low-frequency radiation, I wonder if you could build a big and light radio dish in orbit

dylan604 2y ago
Why not do something similar to VLA instead. So rather than a single "big and light" dish in orbit, you make a constellation of smaller dishes that equal a single larger dish? We know SpaceX is more than capable of that kind of deployment.
- lizknope 2y ago
  I think the scientists don't think it is worth it. The reason we need the James Webb telescope in space is because the infrared wavelengths it studies are absorbed by the Earth's atmosphere. We can observe a lot of the radio spectrum from ground based telescopes https://en.wikipedia.org/wiki/Atmospheric_window https://en.wikipedia.org/wiki/Atmospheric_window https://en.wikipedia.org/wiki/Radio_window https://en.wikipedia.org/wiki/Radio_window https://en.wikipedia.org/wiki/Radio_telescope#Radiotelescopes_in_space https://en.wikipedia.org/wiki/Radio_telescope#Radiotelescope... > Since 1965, humans have launched three space-based radio telescopes. The first one, KRT-10, was attached to Salyut 6 orbital space station in 1979. In 1997, Japan sent the second, HALCA. The last one was sent by Russia in 2011 called Spektr-R. https://public.nrao.edu/ask/are-there-space-based-radio-telescopes/ https://public.nrao.edu/ask/are-there-space-based-radio-tele... > There have been a few radio telescopes launched into space over the years, most with the purpose of linking with ground-based radio telescopes to form an array with very long baselines (distances between antennas). One such recent project, which ceased operation just a few months ago, is RadioAstron. I don’t believe that there are any currently-operating radio telescopes in space, though.
  - namibj 2y ago
    One use would be to hide behind the moon to block interference from Earth, at the L2 point in the earth-moon system. Use a laser to, say, a repeater at L4 or L5, and from there further to either LEO or directly the surface.
- dotnet00 2y ago
  Going off the challenge that doing that for imaging the black holes was, I figure the limiter is the amount of data generated and the amount of processing needed to put it all together.
  - dylan604 2y ago
    That is a fair point, but is that level required to get better data than the VLA but maybe not imaging an black hole? It would be a lot of data to receive via radio especially seeing how the signal being received was radio to start. I'm not intimately familiar with the signal loss from listening under the blanket of the Earth's atmosphere
- ianburrell 2y ago
  Lots of smaller dishes get you resolution but not sensitivity. You can image the black hole at center of galaxy, but you can't detect the red-shifted radio waves from beginning on universe. Also, doing interferometry is much harder when the telescopes are moving.
  - dylan604 2y ago
    You say this as if the earth based ground telescopes are not moving either, which is quite confusing since they most definitely are moving.
    - FredPret 2y ago
      Not relative to one another
      - dylan604 2y ago
        I get it, but even on terra firma, they are having to track relative to each other in 2 axis. In space, they would have to add that 3rd dimension and I stipulate that extra dimension is not linear in complexity. However, tracking on the ground in RA and Dec per object across the distances of VLA is not "simple".

Why not do something similar to VLA instead. So rather than a single "big and light" dish in orbit, you make a constellation of smaller dishes that equal a single larger dish? We know SpaceX is more than capable of that kind of deployment.

lizknope 2y ago
I think the scientists don't think it is worth it. The reason we need the James Webb telescope in space is because the infrared wavelengths it studies are absorbed by the Earth's atmosphere. We can observe a lot of the radio spectrum from ground based telescopes https://en.wikipedia.org/wiki/Atmospheric_window https://en.wikipedia.org/wiki/Atmospheric_window https://en.wikipedia.org/wiki/Radio_window https://en.wikipedia.org/wiki/Radio_window https://en.wikipedia.org/wiki/Radio_telescope#Radiotelescopes_in_space https://en.wikipedia.org/wiki/Radio_telescope#Radiotelescope... > Since 1965, humans have launched three space-based radio telescopes. The first one, KRT-10, was attached to Salyut 6 orbital space station in 1979. In 1997, Japan sent the second, HALCA. The last one was sent by Russia in 2011 called Spektr-R. https://public.nrao.edu/ask/are-there-space-based-radio-telescopes/ https://public.nrao.edu/ask/are-there-space-based-radio-tele... > There have been a few radio telescopes launched into space over the years, most with the purpose of linking with ground-based radio telescopes to form an array with very long baselines (distances between antennas). One such recent project, which ceased operation just a few months ago, is RadioAstron. I don’t believe that there are any currently-operating radio telescopes in space, though.
- namibj 2y ago
  One use would be to hide behind the moon to block interference from Earth, at the L2 point in the earth-moon system. Use a laser to, say, a repeater at L4 or L5, and from there further to either LEO or directly the surface.
dotnet00 2y ago
Going off the challenge that doing that for imaging the black holes was, I figure the limiter is the amount of data generated and the amount of processing needed to put it all together.
- dylan604 2y ago
  That is a fair point, but is that level required to get better data than the VLA but maybe not imaging an black hole? It would be a lot of data to receive via radio especially seeing how the signal being received was radio to start. I'm not intimately familiar with the signal loss from listening under the blanket of the Earth's atmosphere
ianburrell 2y ago
Lots of smaller dishes get you resolution but not sensitivity. You can image the black hole at center of galaxy, but you can't detect the red-shifted radio waves from beginning on universe. Also, doing interferometry is much harder when the telescopes are moving.
- dylan604 2y ago
  You say this as if the earth based ground telescopes are not moving either, which is quite confusing since they most definitely are moving.
  - FredPret 2y ago
    Not relative to one another
    - dylan604 2y ago
      I get it, but even on terra firma, they are having to track relative to each other in 2 axis. In space, they would have to add that 3rd dimension and I stipulate that extra dimension is not linear in complexity. However, tracking on the ground in RA and Dec per object across the distances of VLA is not "simple".