[X] My Assistant

[JRehling]

This thought keeps nagging at me, so I wanted to share it -- figuring the specs comes down to solving some problems in quantum mechanics, which is way out of my expertise, but the idea intrigues me:

Let's say we had an occulting element that was at a good distance from a very large light-gathering telescope. I'm tentatively picturing an occulting element like a fan blade: A central rotating hub with two (or so) wires connected by ballast weights to the hub. Obviously, in space, once you got the rotation going, it would keep going.

The observation event would involve the occulting element passing in front of the object to observe. Let's say Pluto, for example. If the trajectory worked out just right, you could have the planet occulted by a wire crossing the planet first in one dimension, then later by a wire at right angles to that one. If you were collecting photometry data of the planet during those two (or more) events, you could produce an image with pixels as fine as the wire appears to be from the distance between the telescope and the occultor. If the wire were 0.5 mm thick and the distance about 1 AU, the resolution would be extraordinary. And in principle, photometry could be performed with several broadband filters, producing multispectral images with great resolution of distant objects.

Now, for all the problems I've avoided mentioning: There is a direct tradeoff between resolution and time over which you integrate the photometric data. The goal would be to make the occultation last as long as possible, but with objects in different solar orbits, that would be tricky. You'd also want as much light gathering as possible, although you wouldn't necessarily need good resolving power (not even as good as a backyard telescope). The kicker upon which I can't comment is what QM does to light wrapping around the wire and hitting the sensor anyway. Presumably, there's something predictable about that, and maybe it could be divided out in the analysis, without complicating the mechanism. Having the wires be thicker (more like fan blades) would mean that light could only bleed around one edge at a time, rather than two.

It seems like in principle, high resolution multispectral images could be made even of extrasolar planets, even if we had to cover a square kilometer of the Moon with light-gathering telescopes to get the signal-noise high enough.

I don't know what the theoretical limits are, but it seems like we could have Voyager-like images of other solar systems without venturing outside our solar system.

[siravan]

A 100 m mirror working in visible light has a theoretical resolution of approximately 500 nm/100 m = 5x10^-9 radians (500 nm is the wavelength of the green light). At a distant of 1 AU (150x10^9 m), this translates into 750 m. Based on my rudimentary optical knowledge, this means that anything smaller is essentially invisible to the telescope. Note that a distant object (even a small planet) is not a point source to such a telescope, rather it is a diffraction circle of approximately 5x10^-9 radians wide (=0.001 arcseconds) and your mask needs to cover this definite size.