US Military Developing Foldable Space Telescope - Video

The United States military's advanced research arm is working on a foldable space telescope that could image Earth in high resolution at a relatively low cost.

The Defense Advanced Research Projects Agency (DARPA) says the telescope design, known as the Membrane Optical Imager for Real-Time Exploitation, (MOIRE), would be of great use in geosynchronous Earth orbit, the spot 22,000 miles (35,000 kilometers) up where most telecommunications satellites reside.

"Membrane optics could enable us to fit much larger, higher-resolution telescopes in smaller and lighter packages," Lt. Col. Larry Gunn, MOIRE program manager, said in a statement.

The Membrane Optical Imager for Real-Time Exploitation (MOIRE) is in Phase 2 of ground testing. 

If it ever reaches orbit. the telescope is billed as lighter than conventional designs and able to get high-definiton pictures of Earth from geosynchronous orbit.

Credit: DARPA

"In that respect, we’re ‘breaking the glass ceiling’ that traditional materials impose on optics design," Gunn added.

"We’re hoping our research could also help greatly reduce overall costs and enable more timely deployment using smaller, less expensive launch vehicles."

MOIRE is now in Phase 2 of development since work began in 2010. When this phase is completed, a 16-foot (5 meters) prototype of the telescope's mirror should be completed for ground testing.

No space missions have been set for MOIRE yet, DARPA officials said.

There are both advantages and disadvantages to the MOIRE design. The membrane is not as efficient as the usual glass, but it is lighter, which allows prime contractor Ball Aerospace & Technologies Corp. to make larger lenses to increase the telescope's efficiency.

DARPA estimates that a membrane system should weigh 86 percent less than a more traditional system of the same resolution and mass.

The size of the Membrane Optical Imager for Real-Time Exploitation (MOIRE)'s mirror compared with that of the Hubble Space Telescope, the James Webb Space Telescope and Spitzer Space Telescope.

Credit: DARPA

Most telescopes either reflect light (using mirrors) or refract it (using lenses), but MOIRE's behaves differently.

Each membrane will instead diffract light using a piece of equipment known as a Fresnel lens.

"It is etched with circular concentric grooves like microscopically thin tree rings, with the grooves hundreds of microns across at the center down to only 4 microns at the outside edge," DARPA officials said in a statement. "The diffractive pattern focuses light on a sensor that the satellite translates into an image."

DARPA MOIRE: First folding space telescope

Instead of using traditional glass mirrors or lenses, MOIRE seeks to diffract light with Fresnel lenses made from a lightweight membrane roughly the thickness of household plastic wrap. 

MOIRE would house the membranes in thin metal “petals” that would launch in a tightly packed configuration. 

Upon reaching its destination orbit, the satellite would then unfold the petals to create the full-size multi-lens optics.

The capability of orbital telescopes to see wide swaths of the earth at a time has made them indispensable for key national security responsibilities such as weather forecasting, reconnaissance and disaster response.

Even as telescope design has advanced, however, one aspect has remained constant since Galileo: using glass for lenses and mirrors, also known as optics.

High-resolution imagery traditionally has required large-diameter glass mirrors, which are thick, heavy, difficult to make and expensive.

As the need for higher-resolution orbital imagery expands, glass mirrors are fast approaching the point where they will be too large, heavy and costly for even the largest of today's rockets to carry to orbit.

DARPA's Membrane Optical Imager for Real-Time Exploitation (MOIRE) program seeks to address these challenges.

MOIRE aims to create technologies that would enable future high-resolution orbital telescopes to provide real-time video and images of the Earth from Geosynchronous Earth Orbit (GEO)—roughly 22,000 miles above the planet's surface.

Size and cost constraints have so far prevented placing large-scale imaging satellites in GEO, so MOIRE is developing technologies that would make orbital telescopes much lighter, more transportable and more cost-effective.

Currently in its second and final phase, the program recently successfully demonstrated a ground-based prototype that incorporated several critical technologies, including new lightweight polymer membrane optics to replace glass mirrors.

Membrane optics traditionally have been too inefficient to use in telescope optics. MOIRE has achieved a technological first for membrane optics by nearly doubling their efficiency, from 30 percent to 55 percent. The improved efficiency enabled MOIRE to take the first images ever with membrane optics.

With a proposed diameter of 20 meters, MOIRE’s membrane optic “lens” would be the largest telescope optics ever made and dwarf the traditional glass mirrors used in the world’s most famous telescopes.

MOIRE technology houses the membranes in thin metal "petals" that would launch in a tightly packed configuration roughly 20 feet in diameter.

Upon reaching its destination orbit, a satellite would then unfold the petals to create the full-size multi-lens optics.

The envisioned diameter of 20 meters (about 68 feet) would be the largest telescope optics ever made and dwarf the glass mirrors contained in the world's most famous telescopes.