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."

Comments

Magnification?

[JCMay]

The NEI doesn't seem to have any form of magnification; so we'll have a VERY SMALL picture of something VERY FAR away?

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:Magnification?

[torpor]

Define small?

And anyway, its better than what we've got now, which is practically nada ..

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.

Re:Magnification?

[Anonymous Coward]

Magification is usually useless in modern-time astrophotography. What matters (and is correctly mentioned in the article, but hey, who reads that...) is resolution - the ability to discern small details. The resolution doesn't come from magnification, it comes from the ability to gather light from a specific source (compared to the effect of other sources around), and the absence of several possible types of distortion. Large focal length (or rather small focal ratio) is useful for one thing: it enables us to limit light coming from other sources than what we're interested in - decreases the field angle and at the same time limits noise. But with modern CCD photography, it has little importance for magnification, as that is achieved by placing CCD in the right distance from the focal point.

Re:Magnification?

[Profane MuthaFucka]

This telescope is an afocal type. The article mentions specifically that it has a telescope at one end, and a pinhole at the other. That's basically an eyepiece in front of the CCD, so you could definitely calculate a magnification here independent of the resolution of the CCD.

So what do you think of the theoretical limits of resolution? 30 feet doesn't seem to be much of an objective lens for what they are proposing. I would think that diffraction effects would wipe out whatever resolution gains you would hope to achieve. This is only 10 meters, so even on the ground this isn't the biggest scope we could think of, just the longest focal length. This scope would still be diffraction limited to 0.01 arc seconds of resolution, just like Keck (if it were in space).

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.

Huh?

[El]

A pinhole camera, also known as camera obscura, or "dark chamber", is a simple optical imaging device in the shape of a closed box or chamber. So... where are they getting this 10,000 mile long "closed box or chamber"?

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 or at http://www.apo.nmsu.edu/Site/3.5m_Images/telescope 06.JPEG

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:Huh?

[2nd Post!]

The box exists to exclude light from contaminating the image created from the pinhole.

I suppose they'll have to come up with an alternative means of separating the light from the lens and stray light reaching the trailing spacecraft. (From the article)

Inverse Pinhole: Occulation

[G4from128k]

Onc can do similar observations with inverse optics using asteroid occultations. I suppose one could create an artificial asteroid and watch as it passes in front of stars as it orbits or create a detector satellite with an ion engine that visits occultation zones between selected stars and satellites.

OK, I'll hold the part with the pinhole...

[Picass0]

You hold the film and go stand back.

Farther.

Farther.

Farther!

Farther!!

Farther!!!

Yeah, right

[swillden]

There's no way this is going to work. I mean, how the hell are they going to lift into space a pin big enough to poke a 30-foot hole. Where are they even going to *find* a pin that big?

Gotta be the most hare-brained scheme ever. Sheesh.

Re:Yeah, right

[Tablizer]

how the hell are they going to lift into space a pin big enough to poke a 30-foot hole. Where are they even going to *find* a pin that big?

Here's your big needle.

Re:Yeah, right

[spitzak]

Not to mention the danger of keeping that pin anywhere near those inflatable space habitats!

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:Maybe I'm missing something.

[deglr6328]

IANAP but I just can't see how this will work. Imagine a hubble size telescope (still relatively tiny in the scheme of things here) staring at the "pinhole", a couple hundred foot wide hole TEN THOUSAND miles away....What's it going to get, like 10 photons a second or something ridiculous?? Therefore, I would tend to think the exposure times required to create any kind of meaningful image using this scheme would be insanely long....like...weeks. How can you possibly image a planet like earth orbiting its star like that? It's just going to look like a smear due to movement in its orbit and rotation during such a long period.

Think back to the high school elective photography class you probably didn't take. The first thing we did was to make positive images on photo paper with pinhole cameras, I remember distinctly that the exposure times, where you had to sit perfectly still with your little cardboard box, were agonizingly long!!

Yet again, NASA wastes taxpayers $$$s

[Anton Anatopopov]

I am so fed up with NASA wasting taxpayers dollars on what are little more than MIT-style 'hacks'. Why on earth should the taxpayer foot the bill for these boffins to do 'cool' stuff? There should be a clear payoff for any of the money NASA spends. Be it military applications or products that can be commercialised. This 'blue sky' wasting of our hard-earned cash HAS TO STOP!!!

Re:Yet again, NASA wastes taxpayers $$$s

[Anton Anatopopov]

This is not a troll. I am sick of the waste of money that is NASA.

Re:Yet again, NASA wastes taxpayers $$$s

[Tablizer]

Finding earth-like planets is not a waste of money because this planet is getting more crowded and more dangerous. We need more baskets to put our eggs on. Some religious fanatics would kill every human on this planet if they could, and with the progressive ease of building WMD in a garage, someday it will happen (at the current pace). Call it the "Moores-law-of-MWD".

Re:Yet again, NASA wastes taxpayers $$$s

[shobadobs]

Pure science solves loads of problems that applied science never would.

Re:Yet again, NASA wastes taxpayers $$$s

[N3WBI3]

Normally I agere, I would have to see the specifics on what they want. I don think there is a place for pure science and depenging on the proposed budget worthwile..

Re:Maybe I'm missing something.

[Profane MuthaFucka]

That's another good question about this, and I think your description of the problem is right on the money. The f/ratio of this thing is going to be astronomical (pun intended).

On the other hand, the targets it's supposed to look at are bright, and this might not be such a problem if they use extraordinarily sensitive detectors. I know that on Earth, the reason telescopes are getting so much larger is not really for their light gathering ability as for their resolving power. Before adaptive optics, there wasn't much reason to make a scope larger than 2 meters, because the atmosphere limits resolution to about .05 arc seconds, which is also the theoretical limit of a 2 meter scope. Not that adaptive optics are available, scopes are once again getting larger. They're even talking about scopes using interferometry for an effective apeture of 100 meters, strictly for the resolving power.

Rocket Fuel Proposal

[74Carlton]

Time to submit my vinegar and baking soda rocket fuel formula!

Re:Rocket Fuel Proposal

[SuperGlue]

I was thinking along the lines of a very large amount of Match Heads balled up in Aluminum Foil.........

Weeeee

Excellent

[tm2b]

Let's get NASA out of the business of basic space access and back into the basic research without economic incentive that wouldn't be done otherwise.

Ferrying people and objects to space should be a commercial or military activity, instead of NASA trying to be all things to all people