Millimeter-Wave Camera

Traditional SAR imaging at millimeter wave frequencies can provide excellent, high SNR, 3D images of features inside dielectric solids. However, imaging at these frequencies requires thousands of measurements; raster scanning for data collection is time consuming; and data analysis and image rendering requires additional time. These limitations make millimeter wave SAR imaging for nondestructive evaluation prohibitive outside the lab. We propose to show feasibility of overcoming these restrictions by designing a real-time, high-resolution, portable and 3D imaging system for terrestrial and in-space inspection applications. We will demonstrate ability to produce high-fidelity 3D images from substantially reduced data with minimal image quality degradation. We will also investigate further enhancements via spectral estimation or compressive sensing techniques. In Phase I we will design an adaptive, custom sampled, SAR-based millimeter wave imaging system for nondestructive inspection of complex composites and structures. The design of this imaging system will be based on novel and substantial innovations to a well establish knowledge base. The innovations involve overcoming hardware and software limitations that currently make 3D imaging at millimeter wave frequencies slow, cumbersome and impractical for widespread use. Our goal is to design a system with: center frequency in the millimeter wave range; significant bandwidth; high-spatial and range resolutions; rapid image data collection; real-time image rendering; ability to image multi-layer structures made of different materials; high system dynamic range (high detection sensitivity); electrical and mechanical design allowing adaptation to use in-space; modular and frequency-scalablity to accommodate large structures; user friendly design to allow operation by people of various skill sets. The Phase I effort will include simulations and small-scale testing.

We have used similar systems to inspect: Thermal Protection Systems; High Temperature Reusable Surface Insulation; and Advanced Flexible Reusable Insulation. The proposed system would images these materials better and faster. Human Exploration Operations programs, e.g. crew transportation systems; ISS; Orion; deep space habitation; and Advanced Exploration Systems. The NASA/MSFC Meteoroid Environment Office (MEO) could use the system to determine location and depth of simulated micrometeoroids and orbital debris post impact testing. In-service, this capability could be used by people in space to determine the size and depth of debris and impact damage, allowing appropriate repairs. The camera could also be used to inspect multi-layer polymers, Nextel, ceramic fabrics etc such as those used in Whipple bumpers. While the camera cannot image through metal layers, such layers can act as reflectors and enhance imaging in materials above a metal layer. It could also be used to assess damage to the composite overwrap on pressure vessels. The system should be capable of imaging inside any dielectric material, including Kevlar fabrics, Kevlar/epoxy, fiberglass, and foams. The system could also be applied to inspection of more Earthbound applications within the Safety, Security and Mission Services/Construction & Environmental Compliance and Restoration programs. It could image composite, elastomer, polymeric, ceramic and civil materials for degradation.

The proposed systems non-ionizing energy can rapidly image hidden weapons. It can image, in 3D, features hidden inside walls. This includes substructure, pipes, wiring, joists, fasteners, etc through drywall, paneling, siding, plywood and other common materials. It could also be used to detect and determine the extent of damage such as mold, water ingress, termites/carpenter ant nests, etc. A related application would be civil engineering such as inspecting FRP repairs to bridge decks and FRP wraps around concrete columns. In the petrochemical industry, the system could be used to image blockages, build-ups, and damage in fiberglass pipes, tanks and pressure vessels. Microwave testing is being commercialized in the petrochemical industry for inspecting fiberglass vessels. The proposed imaging innovation would greatly expand these capabilities. When a material being tested for radar performance fails radar testing, it is currently difficult to discern the location in the structure that caused failure. We are developing a tool to localize anomalies that caused far field range test failures in radomes. While effective, the tool is raster scanned over the radome. The imaging system proposed here would be a much faster way to localize regions for repair. The same tool could be used to determine if radar absorbers around antennas are functioning properly and to locate anomalies. It could also be used for radar absorbing/low observable coatings for the same purposes.

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

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