Robert D. Bock

Verification of a LWIR hyperspectral landmine model

In this paper the results of our high spatial resolution digital thermal modeling effort are compared against field data. This modeling effort created models for three cases: buried, flush-buried, and surface landmines in combination with a detailed soil model. Under a NVESD airborne countermine data collection program hyperspectral signature data were collected in the LWIR spectral region. These data formed the basis for verification of the signature results generated by our digital hyperspectral landmine model. In particular, hyperspectral thermal signature data were extracted from these airborne countermine measurement data and compared against the results of the digital modeling calculations. Spectral data were extracted from areas on and off identified mine areas and compared against similar areas from our digital model over the same spectral range. The results indicate that good correspondence with the field data was achieved. A discussion of this verification process including the field data extraction procedure, signature modeling computations, and the data comparison results will be presented in this paper.

Impact of shallow buried objects on the spectral properties of terrain features

This paper presents preliminary results of an investigation into the impact of buried objects on the environmental properties and electro-optical spectral characteristics of terrain features. This study focused on the analyses of various sensor information, including hyperspectral and thermal data, collected under a limited set of circumstances; these analyses include laboratory measurements and theoretical computations. A digital terrain model incorporating the relevant physical processes was also constructed to support these investigations. These analyses are particularly relevant to the detection of landmines and the exploitation of hyperspectral sensor data in this application. Results from these analysis efforts will be presented along with example spectral data and computational results.

Application of microgels for optical tagging

In this paper we present results from our research into the use of microgel-based photonic crystals in an optical tagging application. The basis for this research is the phenomena of self-assembly of hydrogel nano- and microparticles (i.e., microgels) into colloidal crystal Bragg reflectors. Previous research has demonstrated the assembly of Bragg structures that are sensitive in the visible spectral region. This current research focuses on the extension of this process into the infrared regime and the use of these infrared-sensitive structures in the creation of an optical tag. In particular, the research effort emphasizes two primary areas: the development of nanoparticles that are infrared-sensitive and the casting of thin films comprised of these particles. We will also present theoretical data on the optical and physical characteristics of thin films comprised of these particles. This paper will present an overview of the program, outline the processes and issues addressed during our initial efforts in creating these infrared sensitive structures and present a summary of the computational results based on the theoretical analyses.

Spectral polarization signature analysis and modeling in the infrared for the detection of landmines

Current electro-optical based landmine detection techniques focus on exploiting phenomena across several wavebands. In particular, polarization signatures have and continue to be a focus of interest for this problem. Our research examined these signatures in the context of a real world environment; specifically, we examined the spectral polarization characteristics of landmines and soils within a complex radiative environment. Our initial results indicate that the optical properties of sand dominate the resultant signature for the buried and flush-buried cases. For surface landmines, the polarization results are dependent on the depth of the soil coating. Therefore, a spectral phenomenological model for the polarization signature of the combined sand-landmine system was developed for the infrared band (mid-wave and long-wave infrared) to study these issues in more detail. The modeling paradigm centered on a radiative transfer approach coupled with heat transfer results to account for incident and emitted radiation simultaneously. This paper will present a description of the physics-based model for the spectral polarization signatures of buried, flush, and surface land mines.

Radial Quantization in Rotating Space–Times

We examine the time discontinuity in rotating space–times for which the topology of time is S1. A kinematic restriction is enforced that requires the discontinuity to be an integral number of the periodicity of time. Quantized radii emerge for which the associated tangential velocities are less than the speed of light. Using the de Broglie relationship, we show that quantum theory may determine the periodicity of time. A rotating Kerr–Newman black hole and a rigidly rotating disk of dust are also considered; we find that the quantized radii do not lie in the regions that possess CTCs.

Analysis of Soil and Environmental Processes on Hyperspectral Infrared Signatures of Landmines

Abstract : Georgia Tech is in the second year of a Multi-University Research Initiative designed to study the impact of environmental processes on optical signatures. In particular, this program is conducting phenomenological studies on hyperspectral and polarimetric signatures of various target classes in the visible and infrared wavebands. Initial research studies have focused on landmines and the impact of various environmental factors and processes (e.g., subsurface processes) on the resultant spectral infrared signatures. A variety of approaches have been employed in this research to gain a better understanding of the impact of the environment on the spectral and polarimetric characteristics of soil and landmine signatures. These approaches include theoretical analyses, physics-based signature modeling, field measurements, and laboratory studies. We will present results from our research into the use of a physics-based, hyperspectral signature model as an analysis tool for landmine-related phenomenology studies. Results from these studies will be presented that underscore the importance of incorporating the subsurface processes into the signature analyses and the impact of these processes on detection algorithm development. The results of these analyses have been propagated to algorithm developers to permit the creation of more robust processing techniques based on these physical analyses and models.

Investigations into soil optical properties and their impact on landmine detection

Recent investigations into the use of new electro-optical sensing modalities for the detection of landmines and other objects in complex backgrounds have led to the need to understand the optical properties of background materials (e.g., soils) in more detail. In particular, the use of spectral and polarimetric signatures in the optical and infrared domains has been the subject of much study; an understanding of soil, foliage, and other background optical properties and their variations is critical to evaluating the utility of these signatures. Our research examined soil emissive and polarimetric signature characteristics in the context of a real world environment; specifically, we examined the spectral properties of landmines and soils within a complex radiative environment. A modified Hapke radiative transfer model was employed to compute these properties. This paper will present a brief overview of those modifications and results of the optical property computations for several scenarios.

Analysis of spectral phenomenology in the detection of landmines

Georgia Tech is leading a spectral phenomenology research effort as a component of a Multi-University Research Initiative; these efforts are focused on studying the impact of environmental processes on electro-optical signatures. In particular, this program is conducting phenomenological studies on hyperspectral and polarimetric signatures of landmines and backgrounds in the visible and infrared wavebands. Research studies have focused on the impact of various environmental factors and processes (e.g., subsurface processes) on the resultant spectral infrared signatures. A variety of approaches have been employed in this research to gain a better understanding of the impact of the environment on the spectral and polarimetric characteristics of soil and landmine signatures. These approaches include theoretical analyses, physics-based signature modeling, field measurements, and laboratory studies. Results from these continuing studies will be presented that underscore the importance of incorporating the environmental processes into the signature analyses and analyze the impact of these processes on detection algorithm development. The results of these analyses have been propagated to algorithm developers to permit the creation of more robust processing techniques.

Investigations into the use of microgel photonic crystals for optical tagging

In this paper we present an update on our research into the use of microgel-based photonic crystals in an optical tagging application. The chemistry of microgel photonic crystals is well established in the visible region of the electromagnetic spectrum. Georgia Tech has recently extended the current visible-band microgel photonic crystal technology into the infrared spectral domain. We have produced infrared-responsive photonic materials from highly monodisperse pNIPAm hydrogels with 400nm (hydrodynamic radius) particles. Both reflection and transmission measurements have been performed on these samples. In addition, we have begun ageing studies and have examined possible ways of increasing the reflection response.

Impact of soil and environmental processes on hyperspectral infrared signatures

In this paper we present results from our research on the impact of various soil types and processes on LWIR broadbandand hyperspectral signatures of landmines and the surrounding soil. These analyses utilized our digital hyperspectral models of the combined landmine-soil system for the computation of these signatures. These physics-based models incorporate models for external environmental processes and allow soil thermal parameters to be set as a function of the subsurface conditions (i.e., porosity, moisture content). Under this research effort, signature computations were conducted for various soil types as a function of the underlying soil conditions in order to examine the relative impact of these conditions on both the broadband and spectral LWIR signatures. Of particular interest were changes in spectral features and contrast changes due to soil water content. Results from the digital signature computations will be presented along with an analysis of the signature features. A comparison of the digital signature calculations to measured data will be included in this discussion. A brief description of the signature model will also be presented.