Ball Aerospace [BLL] is participating in a technology demonstration program for the Defense Advanced Research Projects Agency (DARPA) that has an eventual goal of providing persistent, real-time tactical video to warfighters via a light weight, more transportable and more cost-effective telescope.
Known as the Membrane Optical Imager for Real-Time Exploration (MOIRE), Ball incrementally demonstrated the technologies needed to develop a large, lightweight, space-based telescope for geosynchronous orbit (GEO) using advanced diffractive membrane optics, according to a company statement. MOIRE is demonstrating the manufacturing of large collection area telescopes (up to 20 meters) and the large structures needed to hold the optics tight and flat. MOIRE is also demonstrating the additional optical elements needed to turn a diffraction-based optic into a wide bandwidth imaging device.
It would be optimal to have real-time images and video of any place on the earth at any time, DARPA said in a statement, but, unfortunately, this capability doesn’t currently exist. Aircraft are used to meet much of the military’s imagery requirements, but because of the quantity of aircraft needed and because aircraft do not fly high enough to see into denied territories, spacecraft also play a vital role in providing the imagery data needed for successful military planning and operations.
Spacecraft face their own unique set of challenges when it comes to persistent imagery coverage. The size, or aperture, of the optics needed and the limitations of producing and launching extremely large precision reflective, or mirrored, optics means it is unfeasible to place such a system in GEO orbit, where it could provide persistent coverage.
What makes MOIRE different is the unique diffractive pattern employed on the membranes as opposed to traditional reflecting of light via mirrors. The telescope concept Ball developed employs thin (less than 1/1000th of an inch) transparent membranes etched with a diffraction pattern as the primary optical element used to focus light. The MOIRE program seeks to develop the enabling technologies required for very large optic space platforms that reduce the areal density (the mass of the optics compared to the size of the spacecraft) by four-to-five times of current systems.
“The real value here is that low mass of the membrane and the low cost and the fast development cycle,” Ball Space Sciences Director Makenzie Lystrup told Defense Daily in a recent interview. “So we see that…kind of rapid-cycle, lower-cost, lower-mass option as the real value for some of these applications.”
The big advancement is getting away from the mirrors that are currently used in modern state-of-the-art telescopes like the James Webb Space Telescope (JWST), for which Ball provided the optical telescope portion. Ball believes membrane telescope apertures found on MOIRE could reduce spacecraft mass by a factor of seven, cost by a factor of 10 and development time by a factor of eight. Ball believes instead of taking 24 months to develop a polished, gold-coated beryllium mirror segment like on JWST, it could take three months for one etched transmissive diffractive membrane. Instead of multi-millions of dollars for one mirrored segment, Ball believes it can get one membrane segment for $200,000.
Upon reaching its destination orbit, the MOIRE satellite would then unfold the petals to create the full-size, multi-lens optics. The envisioned diameter of about 20 meters would be what DARPA called the largest telescope optics ever made and dwarf the glass mirrors found in the world’s most famous telescopes.
Ball built the telescope demo, Ball Systems Engineering Department Payload Systems Engineer Jeanette Domber said, and has been focusing lately on testing some of the structures. Domber said Ball recently completed thermal vacuum testing on the primary structure that holds the membrane in place. Domber said that testing went “very well” and that the structure was more stable than the company anticipated.
The DARPA portion of the program will end later this year and Ball is looking for potential customers. In addition to persistent earth observation, Ball believes MOIRE has applications for other capabilities, including remote sensing of greenhouse gases like methane and ethane. It also can provide optical communications as low-weight, large-diameter telescopes can provide high data rate communication links for planetary exploration. It can also perform large aperture astronomy missions as large diameter, lightweight aperture enables high-resolution, low-light science imagery with reasonable mission cost, the company said. MOIRE can also perform exoplanet spectrometry missions.
Nexolve Materials of Huntsville, Ala., developed the membrane for MOIRE.