NASA's Giant Pinhole Camera

Cecil writes "The University of Colorado at Boulder has come up with an interesting proposal, and NASA has decided it has enough merit to give it funding. They're developing what is in essence a pinhole camera where the pinhole is 30 feet wide, and the "film" is tens of thousands of miles away. The "New Worlds Imager" as it is called, may eventually have enough resolution to get visual images of extrasolar planets as small as Earth's moon around stars 100 light years away, and would be able to search them for the key signs of life-as-we-know-it, like oxygen, water, and ozone. Other ideas that NASA will be developing include a lunar space elevator and magnetized beam plasma propulsion."

Re:Magnification?

[Critter92]

"A spacecraft equipped with a telescope would trail tens of thousands of miles behind the starshade to collect and process the light." How about reading the article (all 297 words) before posting?

Re:Huh?

[Profane MuthaFucka]

The dark box isn't necessary if you can restrict the light getting to the film some other way. The article mentioned that the detector would be attached to a telescope, so that would prevent light entering from any place other than the pinhole lens.

Most large telescopes don't have tubes either, since they aren't strictly needed, and they weigh a lot. See the photo of the scope at: http://gemini.physics.ox.ac.uk/photos/geminin-tele scope-lr.gif [ox.ac.uk] or at http://www.apo.nmsu.edu/Site/3.5m_Images/telescope 06.JPEG [nmsu.edu]

Re:Huh?

[Smidge204]

Obviously it does not NEED to be enclosed. The point being that the shade will block most of the light entering the telescope coming from whatever direction the scope is looking. by blocking this "ambient noise" you can get a better image of what you are aiming at.

The reason fro the "enclosed box" is, with a traditional camera, you also have to worry about ambient light from all directions exposing the film. Using a telescope automatically eliminates most of this problem, and in space there isn't much ambient light that would be reflecting off the back of the shade to make a difference.
=Smidge=

Re:Magnification?

[Profane MuthaFucka]

Magnification of a telescope is figured by dividing the focal length of the objective by the focal length of the eyepiece. The type of objective doesn't matter, just it's focal length.

So here, we've got a focal length of 10,000 miles. At the eyepiece end, the article talks about a telescope being mounted there. That telescope would be for all intents and purposes an eyepiece. Don't know what the focal length of that would be, but it would be a very small fraction of the 10,000 miles, making the final magnification of the telescope very large.

Magnetized beam plasma propulsion ?

[Jesrad]

I think the correct name for that is magnetohydrodynamics. It's been researched since the late 60s in various countries (US, France, Russia, and a couple others I think), but it is rumoured that only the US ended up having an applicable, working technology.

Cue to the rumours of Aurora and B2 making use of this to attain crazy hypersonic velocities...

Re:Magnification?

[pfdietz]

Diffraction is how this thing works, and why the telescope is so far back from the shade.

The purpose of the shade is to null out the light from the star without affecting the light from the planet. The shade is extremely effective at doing this, and doing it in a way that is insensitive to wavelength.

I'm not sure they need a hole; using the edge of a large disk should also work.

Re:Magnification?

[John Hasler]

> So here, we've got a focal length of 10,000
> miles.

No you don't. A pinhole doesn't focus.

Forget the "pinhole camera" red herring. This is not a camera or telescope of any kind. As the article says, it is a _starshade_. The angular diameter of the hole from 10,000 miles back is not much larger than the angular diameter of a planet 100 light-years away. Thus viewing the planet through the hole from 10,000 miles back blocks out the light of the star the planet is orbiting.

It's sort of the inverse of an occultation disk.