New Space Telescope Tech Could Be 1,000 Times Sharper Than Hubble

A new type of orbiting telescope could take images more than 1,000 times sharper than those snapped by NASA’s famous Hubble Space Telescope, the technology’s developers say.

Researchers have dubbed their concept the “Aragoscope,” after French scientist Francois Arago, who was the first to discover that light waves diffract around a disk. The Aragoscope would consist of an orbiting space telescope sitting tens or hundreds of miles behind an opaque disk up to 0.5 miles (0.8 kilometers) wide.

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Quite an interesting person, Monsieur Arago:

http://en.wikipedia.org/wiki/Fran%C3%A7ois_Arago#Scientific_studies

A very busy science fellow and a Prime Minister

That image actually makes sense, perhaps. The diffraction of light around the edge of a disk results in what is known as a “Poisson spot” – a bright spot forms in the centre of the shadow made by a disk. Naming it after Poisson is wrong, because Poisson derived it as a trivial consequence of Fresnel’s Equations as an unsuccessful attempt to discredit Fresnel. When the spot was actually found it confirmed Fresnel and disproved Poisson. Calling it the Arago spot makes more sense.

The images show diffraction from a series of concentric ring slits. The focussing ability of this could be calculated from Fresnel’s equations.

A DIY science experiment to test this telescope using a laser pointer and round-headed pin is http://physicsed.buffalostate.edu/pubs/StudentIndepStudy/EURP09/Spot/spot.html
To use this to test the focal length and focussing ability of the space telescope replace the pinhead with a black disk surrounded by black concentric circles printed on a transparent film (i.e. a mask). Try out several different combinations of dimensions of radii for the concentric circles.

To work out the best mathematical spacing of concentric circles for the mask, and assuming that you don’t want to solve the full Fresnel equations, use Huygens principle of treating each unmasked ring of light from the mask as a light source.

What you want is the exact opposite of what is known in astronomy as an “Apodizing”. Apodizing is the process of setting up a mask to minimise the effects of diffraction.

mollwollfumble said:

That image actually makes sense, perhaps. The diffraction of light around the edge of a disk results in what is known as a “Poisson spot” – a bright spot forms in the centre of the shadow made by a disk. Naming it after Poisson is wrong, because Poisson derived it as a trivial consequence of Fresnel’s Equations as an unsuccessful attempt to discredit Fresnel. When the spot was actually found it confirmed Fresnel and disproved Poisson. Calling it the Arago spot makes more sense.

The images show diffraction from a series of concentric ring slits. The focussing ability of this could be calculated from Fresnel’s equations.

A DIY science experiment to test this telescope using a laser pointer and round-headed pin is http://physicsed.buffalostate.edu/pubs/StudentIndepStudy/EURP09/Spot/spot.html
To use this to test the focal length and focussing ability of the space telescope replace the pinhead with a black disk surrounded by black concentric circles printed on a transparent film (i.e. a mask). Try out several different combinations of dimensions of radii for the concentric circles.

To work out the best mathematical spacing of concentric circles for the mask, and assuming that you don’t want to solve the full Fresnel equations, use Huygens principle of treating each unmasked ring of light from the mask as a light source.

What you want is the exact opposite of what is known in astronomy as an “Apodizing”. Apodizing is the process of setting up a mask to minimise the effects of diffraction.

I see a problem which explains why this hasn’t been used up until now. The distance for best possible focussing is L = d^2/λ where d is the diameter of the circular ring on the mask and λ is the wavelength of light. In a nutshell, different diameters are needed for different wavelengths at the same focus length. Using concentric rings won’t focus properly at a given wavelength. So either some mechanical method is needed to open and close rings on the mask to ensure that only one ring is open at one time, or a single ring and the detector slides back and forth a large distance, or a single ring with multiple detectors used at different distances with a filter on each.I bet they’re planning on using a mechanical method to open only one ring at a time.