In physics, a moire pattern is an interference pattern created when two grids are overlaid at an angle, or when they have slightly different mesh sizes. It’s an appropriate name for DARPA’s Membrane Optic Imager Real-Time Exploitation (MOIRE) project, which aims to use diffractive optic membranes to conduct tactical video surveillance from space. That’s very useful when looking at territory where an intruding UAV is likely to be shot down, or when conducting operations to find, say, mobile SCUD missiles within a large potential area.
Making that happen involves a 20-meter diameter optic membrane surveying an area of more than 10 x 10 km at least once a second, with ground resolution better than 2.5 meters, and the ability to detect moving vehicles. Field of regard would be larger, of course, at 10 million square kilometers that could be covered from geosynchronous orbit. Finally, all of this has to cost less than $500 million per copy. How hard could all that be? Hard enough for DARPA, apparently…
DARPA’s MOIRE Program
Scientists have believed for over a decade now that diffractive optical membranes have great potential for space telescope applications, given their potential performance and especially their light weight, which lowers launch costs. They’re made by using a lightweight membrane optic that’s held very flat. It’s etched with a diffractive pattern, which is used to focus light on a sensor.
DARPA believes that a system like that may also have potential for staring through the atmosphere. Despite the $500 million per satellite ceiling, a comparison to the operational costs and risks of conducting that surveillance by other means in hostile territory means that MOIRE could actually be a cost improvement. Nor has the US military forgotten the immense difficulty it had in finding Iraqi SCUD mobile ballistic missiles during the 1991 Desert Storm war, despite its full control of the air.
In terms of geosynchronous, wide area, medium-to-high resolution imaging, MOIRE would be the only game in town. The size of the optics needed, and the limitations of producing and launching extremely large precision glass optics, make it infeasible to place a conventional optical system with that capability in geosynchronous earth orbit (GEO).
DARPA sees the following as key technical factors for MOIRE:
1. Large low cost, lightweight, deployable, diffractive membrane optics for geosynchronous orbit imaging systems.
2. Near real time image stabilization and tactical geolocation knowledge, exploiting exquisitely accurate attitude determination and control systems and ground truth controls.
3. A telescope design that increases spectral bandwidth
4. Stability and dynamics of the large MOIRE structure in geosynchronous orbit
5. Target motion detection capability for highway speeds (later revised to “target motion detection capability at > 0.1 Hz”).
6. Probability of detection for a SCUD-class [missile] launch of 0.99, with less than one false alarm per month.
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DARPA’s announcement envisioned a pair of $4-5 million awards in Phase 1, designed to validate the optical prescription, design and structure, and remove major optical risks. They’ll perform testing on a 1 meter diameter primary optic, and on “coupons” of key materials used. Ball Aerospace and Nexsolve Corp. appear to have received the awards. Phase 1 ended with a System Concept Design Review and a Payload Preliminary Design Review.
DARPA expected a $30-40 million award for Phase II, which came to pass in September 2011 with an award to Ball Aerospace. Phase 2 will produce and test a 5 meter brassboard telescope, showing a technological path to flight aboard a satellite. Membrane fabrication must also be trace-to-flight, and phase 2 will incorporate either sub-scale or fractional demonstration of the system’s unfurling in space. Phase 2 will end with a System Preliminary Design Review.
If there is a Phase III, it would be the subject of a separate solicitation. A Critical Design Review (CDR) will be conducted early in this phase, which is necessary because DARPA is thinking in terms of designing, building, launching, and demonstrating a deployable 10 meter diffractive optics space telescope in geosynchronous orbit. This on-orbit demo would validate modeling, simulation and ground testing done in Phases 1 and 2, and show traceability to an operational 20 meter system meeting MOIRE’s final goals. Still, space launch isn’t cheap – not even as a secondary payload with a launch mass under 1000 kg/ 2,200 pounds on an EELV-M class medium rocket.
Contracts & Key Events
Unless otherwise noted, the US Defense Advanced Research Projects Agency (DARPA) manages the contracts.
Dec 5/13: Testing. DARPA has some good news from the program. Based on the results of tests, a system using MOIRE optics would weigh about 1/7 as much (85.7% reduction) as a traditional system with the same resolution and mass. On the other hand, it looks like they won’t be launching an actual satellite. From DARPA, “First Folding Space Telescope Aims to “Break the Glass Ceiling” of Traditional Designs”:
“Currently in its second and final phase, the program recently successfully demonstrated a ground-based prototype that incorporated several critical technologies…. 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…. glass… is nearly 90 percent efficient, [but membrane optics’] much lighter weight enables creating larger lenses that more than make up the difference…. As a proof of concept, the MOIRE prototype validates membrane optics as a viable technology for orbital telescopes.”
Sept 2/11: Ball Aerospace Corp. in Boulder, CO receives a $36.9 million cost-plus-fixed-fee contract for Phase 2 of the MOIRE Program.
Work will be performed in Broomfield, CO (73.2%); Livermore, CA (7.2%); Goleta, CA (17.2%); and Huntsville, AL (2.4%). Work is expected to be complete by Feb 10/13 (HR0011-10-C-0157).
MOIRE Phase 2
July 25/11: Lawrence Livermore National Labs’ Photon Science & Applications (PS&A) group completes its first 80 cm diameter, 18-micron thick diffractive membrane optic, designed in partnership with Ball Aerospace and Nexsolve Corp., for DARPA’s MOIRE program. The membrane was printed and etched with 4-micron-wide critical dimensions, and will be tested at Ball Aerospace facilities in early demonstrations of MOIRE technology. LLNL.
Oct 1/10: DARPA releases its Broad Agency Announcement solicitation #DARPA-BAA-10-51: MOIRE – Membrane Optic Imager Real-Time Exploitation.
Based on subsequent information, it seems that Ball Aerospace and Nexsolve Corp. each won $4-5 million contracts to proceed with Phase 1.
MOIRE Phase 1
Feb 26/10: DARPA announces a MOIRE Proposers’ Day on March 12/10, in support of a planned Broad Agency Announcement (DARPA BAA 10-51). On March 5/10, the event is canceled. On the other hand, the solicitation retain value as a preliminary look at DARPA’s objectives for MOIRE. FBO.gov | Aviation Week.
* Federation of American Scientists – National Image Interpretability Rating Scales. MOIRE is a NIIRS 3.5+ project.
* Optics Infobase – Fabrication of Large-Aperture Lightweight Diffractive Lenses For Use in Space. From Applied Optics, Vol. 40, Issue 4, pp. 447-451 (2001).