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NIA Seminar by Dennis Gregoris |
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Date: September 19, 2006
Time: 9:30am
Location: NIA, Rm 137
Additional Information: Presentation (.pdf)
Multispectral Imaging for Ice and Frost Contamination Detection and Measurement
Dennis Gregoris, MDA Corporation, Canada
The ability to detect thin layers of ice on aircraft wings, road pavement and even the Space Shuttle has important safety ramifications. Clean aircraft wings and other critical aircraft surfaces are of vital importance for safe flight operations. At present, the de-icing technicians and pilots make visual or tactile inspections. However, ice contamination can be difficult to see and a thorough inspection of all critical surfaces can be time consuming. Road ice conditions are also important to monitor for safety and maintenance reasons but often difficult to assess visually. Finally, the tragic loss of the Space Shuttle Columbia caused by debris from the cryogenic external fuel tank has underscored the need to detect potential ice debris on the exterior of the fuel tank. Augmenting or replacing human visual inspection with an automatic system will increase safety through improved reliability, thoroughness and speed of the inspection.
There are contact and non-contact ways to detect ice contamination. Contact methods require physical contact between the sensing device and the contaminant. They determine the presence of ice through a change in the acoustic or electrical properties of the material in contact with the sensor. However, due to their point sensor nature, they only offer sparse and localized inspection coverage of a surface. In contrast, non-contact or remote sensing methods offer flexibility in the location of the inspected surface and the time needed to measure a given area. This presentation discusses current remote sensing ice detection approaches that operate in some part of the electromagnetic spectrum between the millimeter wave region and the visible optical region. Several physical properties can be exploited by an electro-optic approach including: optical interference effects, internal reflection, surface scattering, polarization, and spectral reflectance. Of these, spectral reflectance offers a simple and effective means for detecting ice. Infrared spectral analysis techniques offer a viable solution to the problem of detecting ice on various surfaces such as aircraft, roads and the space shuttle external tank. Imaging systems implementing these techniques can be used to support, and eventually replace, manual inspection methods involving de-icing technicians and pilots. The theory and application of a unique multispectral infrared
(Spectral) camera that promises to meet the need for improved automated ice detection will be discussed in detail during the course of the presentation.
This Spectral camera employs a reflectance spectroscopy technique to produce reliable, robust detection of ice layers less than 0.5 mm thick at operationally useful ranges and on a variety of different surfaces including painted and unpainted aircraft surfaces, road pavement and the insulation foam of the Space Shuttle External Tank. Furthermore, ice can be sensed beneath layers of water, Type I, II and IV de-icing fluids.
The presentation reviews the requirements, technology and experimental results of a prototype multispectral camera system developed for remote imaging of ice on various surfaces. Applications of the technology are also reviewed.
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