The excitation-emission matrix (EEM) is the luminescence spectral emission intensity of fluorescent compounds as a function of the excitation wavelength. EEMs offer the promise of an additional degree of information for enhanced compound detection and identification. Veridian has collected pure-component EEMs of amino acids (Trp, Phe, Tyr), Bacillus globigii (bg), Bacillus thuringiensis (bt,), and selected backgrounds. Also collected were EEMs of mixtures of amino acids and of bg in solution with a few backgrounds. The EEMs of pure components and mixtures were analyzed for phenomenology and for potential methods of unmixing and identifying the constituents of EEMs having mixed components of a similar nature.
Radiometrically calibrated hyperspectral imagery contains information relating to the material properties of a surface target and the atmospheric layers between the surface target and the sensor. All atmospheric layers contain well-mixed molecular gases, aerosol particles, and water vapor, and information about these constituents may be extracted from hyperspectral imagery by using specially designed algorithms. This research describes a total sensor radiance-to-ground reflectance inversion program. An equivalent surface-pressure depth can be extracted using the NLLSSF technique on the 760nm oxygen band. Two different methods (APDA, and NLLSSF) can be used to derive total columnar water vapor using the radiative transfer model MODTRAN 4.0. Atmospheric visibility can be derived via the NLLSSF technique from the 400-700nm bands or using an approach that uses the upwelled radiance fit from the Regression Intersection Method from 550nm-700nm. A new numerical approximation technique is also introduced to calculate the effect of the target surround on the sensor-received radiance. The recovered spectral reflectances for each technique are compared to reflectance panels with well-characterized ground truth.
An end-to-end hyperspectral system model with applications to space and airborne sensor platforms is under development and testing. In this paper we discuss current work in the development of the sensor model and the results of preliminary testing. It is capable of simulating collected hyperspectral imagery of the ground as sensors operating from space or airborne platforms would acquire it. Dispersive hyperspectral imaging sensors operating from the visible through the thermal infrared spectral regions can be modeled with actual hyperspectral imagery or simulated hyperspectral scenes used as inputs. In the sensor model portion, fore-optics (misalignment), dispersive spectrometer designs, degradations (platform motion, smile, keystone, misregistration), focal plane array (temperature drift, nonuniformity/nonlinearity), noise (shot, dark, Johnson, 1/f, RMS read, excess low frequency), analog-to-digital conversion, digital processing, and radiometric/temporal/wavelength calibration effects are included. The overall model includes a variety of processing algorithms including constant false alarm rate anomaly detection, spectral clustering of backgrounds for anomaly detection, atmospheric compensation, and pairwise adaptive linear matching for detection and classification. Results of preliminary testing using synthetic scene data in the visible/near infrared portion of the spectrum are discussed. Potential applications for this modeling capability include processing results performance prediction and sensor parameter specification trade studies.
In December 1997, the U.S. Department of Energy (DOE) established a Center of Excellence (Hyperspectral- Multispectral Algorithm Research Center, HyMARC) for promoting the research and development of algorithms to exploit spectral imagery. This center is located at the DOE Remote Sensing Laboratory in Las Vegas, Nevada, and is operated for the DOE by Bechtel Nevada. This paper presents the results to date of a research project begun at the center during 1998 to investigate the correction of hyperspectral data for atmospheric aerosols. Results of a project conducted by the Rochester Institute of Technology to define, implement, and test procedures for absolute calibration and correction of hyperspectral data to absolute units of high spectral resolution imagery will be presented. Hybrid techniques for atmospheric correction using image or spectral scene data coupled through radiative propagation models will be specifically addressed. Results of this effort to analyze HYDICE sensor data will be included. Preliminary results based on studying the performance of standard routines, such as Atmospheric Pre-corrected Differential Absorption and Nonlinear Least Squares Spectral Fit, in retrieving reflectance spectra show overall reflectance retrieval errors of approximately one to two reflectance units in the 0.4- to 2.5-micron-wavelength region (outside of the absorption features). The results are based on HYDICE sensor data collected from the Southern Great Plains Atmospheric Radiation Measurement site during overflights conducted in July of 1997. Results of an upgrade made in the model-based atmospheric correction techniques, which take advantage of updates made to the moderate resolution atmospheric transmittance model (MODTRAN 4.0) software, will also be presented. Data will be shown to demonstrate how the reflectance retrievals in the shorter wavelengths of the blue-green region will be improved because of enhanced modeling of multiple scattering effects.