Replicated Diffractive Optics/MOIRE
Membrane Optical Imager for Real-Time Exploitation
Artist concept, image credit DARPA
Very large aperture telescopes can meet a growing range of requirements for space-based missions. Embarking on those new missions is often hampered by launch vehicle size, development time and cost issues related to aperture size. Demonstrating agility to innovate, Ball’s revolutionary approach for very large aperture telescopes uses replicated diffractive optics to reduce cost and development time.
Ball Aerospace has developed a telescope design that uses diffractive membrane optics that are manufactured using replicative techniques, overcoming time and cost limitations imposed on traditional reflective large aperture space telescope designs. Ball’s game-changing approach allows the production of 20 meter-plus apertures that dwarf any space telescope currently under development. This design can be used for many narrow spectral bandwidth applications.
Working under a contract awarded in 2010 from the Defense Advanced Research Projects Agency (DARPA), Ball developed the Membrane Optical Imager for Real-Time Exploitation (MOIRE). The technology matured for the MOIRE program enables narrow-band, persistent, real-time video of areas on the Earth from geosynchronous orbit 22,000 miles above the surface.
The telescope concept that Ball developed employs thin (less than 1/1000th of an inch) transparent membrane segments etched with a diffraction pattern as the primary optical element used to focus light. The narrow-band, large collection area technology can be rapidly manufactured, significantly reducing cost compared to reflective systems, and is extremely lightweight, enabling the use of existing launch vehicles.
A complete end-to- end demonstration telescope, utilizing a 45 degree wedge of a 5 meter primary optical element was assembled. The optical and imaging quality of the telescope was measured for a single panel with color correction over a narrow spectral bandwidth, showing the quality imaging capabilities of this new technology.
Two segments of a 10 meter primary optical element with flight-like hinges have been tested for deployment repeatability. In May 2014, two sections of the primary composite back structure and the structure deployment hinges successfully underwent environmental tests to simulate the temperature range and vacuum of a space environment. This environmental testing competed the final phase of the DARPA MOIRE risk reduction program and increased the technology readiness level for future uses.
Replicated diffractive optics in very large telescope apertures can be used for many applications, including persistent surveillance, long distance optical communications, Earth science and targeted astrophysics missions. Some examples are remote sensing of greenhouse gases like methane and ethane, high data rate communication links for planetary exploration, and large aperture astronomy missions because large diameter, lightweight aperture telescopes enable high-resolution, low-light science imagery at a reasonable mission cost.
The MOIRE telescope will also be able to perform exoplanet spectrometry missions, a follow on step for the Kepler mission, which Ball led as prime contractor. Recently Ball delivered the optical element for the James Webb Space Telescope, which will be the largest aperture telescope to fly in space.
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