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 by 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.
Instead of reflecting light with mirrors or refracting it with lenses, MOIRE’s membrane optics diffract light. Roughly the thickness of household plastic wrap, each membrane serves as a Fresnel lens–it is etched with circular concentric grooves like microscopically thin tree rings. The diffractive pattern focuses light on a sensor that the satellite translates into an image.
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.
