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Proceedings Paper

Millimeter-wave radiometric measurements of a treeline and building for aircraft obstacle avoidance
Author(s): David A. Wikner
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Paper Abstract

Passive millimeter-wave (MMW) imagers have the potential to be used on low-flying aircraft for terrain-following / terrain-avoidance during low-visibility conditions. This potential exists because of the inherent nature of MMW radiation that allows it to penetrate many visible and IR obscurants such as fog, clouds, and smoke. The phenomenology associated with this application, however, has not been fully explored. Specifically, the radiometric signatures of the various obstacles that might be encountered during a low-altitude flight need to be thoroughly understood. The work described in this paper explores the 93-GHz passive signature of a deciduous treeline and a concrete/glass building. The data were taken from the roof of a 4-story building to simulate the view of a low-flying aircraft. The data were collected over many months with an ARL-built Stokes-vector radiometer. This radiometer is a single-beam system that raster scans over a scene to collect a calibrated 93-GHz image. The data show the effects of weather and tree lifecycle on the 93-GHz brightness temperature contrast between the horizon sky and the obstacles. For the case of trees, it is shown that the horizon sky brightness temperature is greater than that of the trees when the leaves are on because of the reflective properties of the leaves. This made the trees quite detectable to our system during the late spring, summer, and early fall. Concrete buildings are inherently low-contrast obstacles because their vertical nature reflects the horizon behind the sensor and can easily mimic the forward horizon sky. Solar loading can have a large effect on building signatures.

Paper Details

Date Published: 20 August 2003
PDF: 9 pages
Proc. SPIE 5077, Passive Millimeter-Wave Imaging Technology VI and Radar Sensor Technology VII, (20 August 2003); doi: 10.1117/12.487901
Show Author Affiliations
David A. Wikner, U.S. Army Research Lab. (United States)

Published in SPIE Proceedings Vol. 5077:
Passive Millimeter-Wave Imaging Technology VI and Radar Sensor Technology VII
Roger Appleby; Robert Trebits; David A. Wikner; James L. Kurtz, Editor(s)

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