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DARPA developing giant folding space telescope


December 8, 2013

Artist's concept of the foldable plastic telescope

Artist's concept of the foldable plastic telescope

Image Gallery (5 images)

DARPA has announced planes to use a foldable plastic lens to “break the glass ceiling” of space telescopes. It’s part of the agency’s Membrane Optical Imager for Real-Time Exploitation (MOIRE) program, which aims at replacing conventional glass optics with lightweight polymer membranes that may one day make possible a foldable plastic orbital telescope 20 m (65 ft) wide that will be capable of seeing a medium-sized dog on Earth from 36,000 km (22,000 mi) away.

Putting telescopes into Earth orbit was one of the earliest and most successful goals of the space age. They’ve revolutionized astronomy with the groundbreaking discoveries of the Hubble and Kepler missions soon to be added to by the planned James Webb Space Telescope. Less obvious, but equally important are the telescopes that point in the other direction to keep an eye on the Earth for tasks ranging from weather forecasting to military reconnaissance.

The problem is that these telescopes are based largely on glass lenses and mirrors. These do a splendid job with an efficiency of 90 percent, but glass has its limitations – not the least of which is its weight. Glass is heavy. On Earth, telescope mirrors are limited in size because they start to deform under their own weight. In space, its even worse because, according to DARPA, optics in satellites are rapidly reaching the point where putting a larger mirror into orbit will be beyond the power of the largest rocket.

Section of the MOIRE membrane optic

DAPRA’s solution to this is its MOIRE program, which aims to sidestep the whole glass problem with optics made out of a lightweight polymer membrane that is not only of comparable quality to glass, but can also be folded.

MOIRE is a two-phase project aimed at creating technologies that could be used to place a future high-resolution orbital telescope in geostationary orbit for real-time video surveillance of the Earth. It uses a polymer membrane that is the thickness of household plastic wrap. This membrane doesn’t reflect or refract light like conventional mirrors and lenses. Instead, it diffracts it like a Fresnel lens by means of microscopic concentric grooves etched into the plastic. These grooves range in size from hundreds of microns wide down to only four microns.

The optical membrane is less efficient than glass, but it makes up for this in size. And since it’s lightweight and can fold up, an orbital polymer telescope’s size can be very big without weighing much. DARPA estimates that such telescopes will be one-seventh the weight of a comparable glass-mirrored version.

Size comparison of the foldable optic and conventional telescope mirrors

The idea is that the membranes would be mounted in thin metal petals that would fold up like origami to form a spacecraft about 6 m (20 ft) in diameter. Launched into geostationary orbit, the satellite would unfold a long support structure with the membrane lens at one end and a sensor suite at the other. The lens would then unfold to a diameter of 20 m (65 ft) and focus light on the sensors to form images.

According to DARPA, this would be the single largest telescope ever built – twice the size of the ground-based twin 10-m Keck telescopes. From its geostationary position, it would see about 40 percent of the Earth’s surface at a resolution of one meter while generating videos at one frame per second.

MOIRE is now in its second and final phase. With Ball Aerospace & Technologies as the primary contractor, MOIRE demonstrated a ground-based, proof-of-concept prototype. This consists of a section of a 5-m wide optic using polymer membranes to replace glass and the development of the secondary optics needed to operate the telescope. Aside from achieving the proper flatness and stability, the MOIRE telescope scored a first for membrane optics by nearly doubling their efficiency from 30 to 55 percent and creating the first images ever with membrane optics.

Concept of a space-based polymer telescope

DARPA says that the next part of Phase 2 will be an orbital test of the optical membrane as part of the US Air Force FalconSAT-7 program.

“Membrane optics could enable us to fit much larger, higher-resolution telescopes in smaller and lighter packages,” says Lt. Col. Larry Gunn, DARPA program manager. “In that respect, we’re ‘breaking the glass ceiling’ that traditional materials impose on optics design. We’re hoping our research could also help greatly reduce overall costs and enable more timely deployment using smaller, less expensive launch vehicles.”

The video below shows how the 20-m telescope would deploy.

Source: DARPA

About the Author
David Szondy David Szondy is a freelance writer based in Monroe, Washington. An award-winning playwright, he has contributed to Charged and iQ magazine and is the author of the website Tales of Future Past.   All articles by David Szondy

I'll go with a segmented mirror that is assembled is space.

8th December, 2013 @ 09:59 pm PST

Possible collisions with space trash seems like a problem.

8th December, 2013 @ 11:04 pm PST

George Orwell only got the date wrong.

Mel Tisdale
9th December, 2013 @ 03:24 am PST

Mel got it right. Starting out, the story looked like it would be a great way for looking deeper and better into space (it should be useful for that too) but the article lets us know that it's primarily for looking at earth, by DARPA.

Bob Tackett
9th December, 2013 @ 08:31 am PST

Well, since the NRO's keyhole satellites can resolve down to 4 inches (probably less - that's what declassified) it's not as if world watching scopes haven't been around for decades anyway. This is just a lighter technology with potentially more weakness (as @oskarsb points out)

9th December, 2013 @ 08:53 am PST

I doubt the new thinking robots will follow Azimov's rules of robotics.....

9th December, 2013 @ 12:58 pm PST

It would be great if they developed this technology to better see the universe, but to better able to spy on us with it??

Stacy Ann Young
9th December, 2013 @ 02:05 pm PST

They're pointing it in the wrong direction.

9th December, 2013 @ 03:58 pm PST

@ dsiple

Walking in a park on a sunny day can be seen as harm coming to you. All that nasty UV.

Asimov's 3 laws of robotics are poorly thought out.

9th December, 2013 @ 09:36 pm PST

Are they developing an energy weapon?

Kris Lee
11th December, 2013 @ 01:13 pm PST

It's a bitter statement about humankind and the USA in particular: Clever minds build a wonderful new telescope, which lesser minds of greed and fear point back at Earth.

John Matthias
13th December, 2013 @ 09:56 pm PST
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