“Contrary to Hollywood’s ideas, today’s spy satellites that orbit the Earth at fast speeds and relatively lower altitudes can only snap photos for the U.S. military and intelligence agencies. Taking live video of a single location would require satellites to hover by matching the Earth’s rotation in geosynchronous orbit about 22,000 miles (36,000 kilometers) high — but creating and launching a space telescope with the huge optics arrays capable of seeing ground details from such high orbit has proven difficult.
If all goes well, U.S. military commanders and intelligence agents may someday get live streaming video and up-to-date images of battlefields or trouble spots around the world. Such capability could complement the swarms of cheap drones providing battlefield surveillance today, and might even spare the U.S. embarrassment from losing spy drones over Iran or other countries.” –Innovation News Daily
To meet national security requirements around the world, it would be optimal to have real-time images and video of any place on earth at any time—a capability that doesn’t currently exist. Today, aircraft are used for some imagery requirements. Because of the huge quantity of aircraft needed, and because aircraft do not fly high enough to see into denied territories, spacecraft are also used for imagery requirements.
Spacecraft, however, face different challenges in providing persistent coverage. The size (aperture) of the optics needed, and the limitations of producing and launching extremely large precision glass optics means it is infeasible to place such a system in geosynchronous earth orbit (GEO), approximately 36,000 kilometers high, where it could provide persistent coverage.
MOIRE is a GEO-based system that uses a lightweight membrane optic etched with a diffractive pattern. The diffractive pattern is used to focus light on a sensor. The MOIRE program seeks to enable the technologies required for these very large optics for space platforms. The program aims to demonstrate the manufacturability of large membranes (up to 20 meters), large structures to hold the optics flat, and also demonstrate the secondary optical elements needed to turn a diffraction-based optic into a wide bandwidth imaging device.
Source: DARPA
Recent News: Ball Aerospace Completes Preliminary Design Review for MOIRE – December 12, 2011
