John R. Hummel

Thermal modeling in the Smart Weapons Operability Enhancement program, Part 1: natural terrain backgrounds without vegetation

The Smart Weapons Operability Enhancement (SWOE) Program has developed a package of databases, physics and scene rendering models, and analysis procedures that can be used by developers and testers of smart weapons to test and evaluate future smart weapons systems under realistic environmental conditions and natural backgrounds. This resource is being used to evaluate both infrared and millimeter wave systems. In the case of infrared systems, the driving force for the radiant fields that are ultimately sensed are the temperature fields in the scene. In the SWOE Program, a series of detailed thermal models are used to calculate the temperature conditions of the surfaces and objects in the scene. These models can be used to calculate the temperatures for a variety of surfaces and a full range of environmental conditions, including winter and non-winter conditions. This paper summarizes the one dimensional heat conduction model that is used to calculate the temperature conditions for surfaces without vegetation.

Obtaining surface optical properties from space-based lidar systems

Space-based lidar systems are planned for a number of applications. One application being considered is to use a space-based lidar to infer information about the visibility near the surface from remote or inaccessible areas. This can be accomplished if one can obtain information about the optical properties near the surface. The concept would involve using a lidar on a space platform probing the atmosphere and underlying surface along its orbital path. The purpose of this research has two goals. The first is to determine if a unique relationship can be found at a suitable laser wavelength to relate the extinction coefficients near the surface to the visibility at the surface. The second goal is to determine if lidar back scatter measurements can be inverted in a reasonable fashion to obtain the extinction coefficient near the surface. If these goals can be met, then visibility can be obtained on a routine basis from space-based lidars. This paper presents the results from the study. In the study, a number of different lidar wavelengths have been studied to see if one is more suitable than the others. Also, an examination of the assumptions required to perform the inversion of the lidar equation has been made.

Thermal and radiometric modeling of terrain backgrounds

The U.S. Army Cold Regions Research and Engineering Laboratory (CRREL) is administering a multi-year, multi-agency infrared background data and modeling program entitled Smart Weapons Operability Enhancement (SWOE). This paper describes the progress made to date in model development and integration, under the direction of the Geophysics Directorate of the Air Force Phillips Laboratory. Other aspects of the program, not described here, include measurements and database development. A 1-D thermal model for natural backgrounds has been developed that covers a full range of background types. The range of types includes vegetated and nonvegetated surfaces, winter conditions, porous materials, and the presence of soil moisture. The model is also being used as a test bed for the development of a full 3-D model for natural backgrounds. The temperatures computed with this model are designed to be input to the radiometric models. Two models have been developed to compute the infrared radiances of natural background scenes, with both spectral and spatial capability. The first model computes radiances from terrain or water, while the second is used for modeling of discrete 3-D objects, such as trees, buildings, and vehicles. Both radiometric models includes thermal emission and reflections of the sun and sky. Atmospheric transmission and radiance are included. The terrain and objects may have spatially-varying temperatures and surface coatings. Emittances and reflectances are spectral and directional/bi- directional. Radiances computed with these models are translated to a Computer Image Generator (CIG) run by the U.S. Army Engineering Topographic Laboratory (ETL) for image rendering.