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NASA NTRS1997

Image registration by parts

In spite of the large number of different image registration techniques, most of these techniques use the correlation operation to match spatial image characteristics. Correlation is known to be one of the most computationally intensive operations and its computational needs grow rapidly with the increase in the image sizes. In this article, we show that, in many cases, it might be sufficient to determine image transformations by considering only one or several parts of the image rather than the entire image, which could result in substantial computational savings. This paper introduces the concept of registration by parts and investigates its viability. It describes alternative techniques for such image registration by parts and presents early empirical results that address the underlying trade-offs.

Chalermwat, Prachya↗
NASA NTRS1998

IMAGE Mission Science

Simultaneous, global measurement of major magnetospheric plasma systems will be performed for the first time with the Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) Mission. The ring current, plasmasphere, and auroral systems will be imaged using energetic neutral and ultraviolet cameras. Quantitative remote measurement of the magnetosheath, plasmaspheric, and magnetospheric densities will be obtained through radio sounding by the Radio Plasma Imager. The IMAGE Mission will open a new era in global magnetospheric physics, while bringing with it new challenges in data analysis. An overview of the IMAGE Theory and Modeling team efforts will be presented, including the state of development of Internet tools that will be available to the science community for access and analysis of IMAGE observations.

Gallagher, D. L.↗
NASA NTRS1998

Auroral Observations from the POLAR Ultraviolet Imager (UVI)

Because of the importance of the auroral regions as a remote diagnostic of near-Earth plasma processes and magnetospheric structure, spacebased instrumentation for imaging the auroral regions have been designed and operated for the last twenty-five years. The latest generation of imagers, including those flown on the POLAR satellite, extends this quest for multispectral resolution by providing three separate imagers for the visible, ultraviolet, and X ray images of the aurora. The ability to observe extended regions allows imaging missions to significantly extend the observations available from in situ or groundbased instrumentation. The complementary nature of imaging and other observations is illustrated below using results from tile GGS Ultraviolet Imager (UVI). Details of the requisite energy and intensity analysis are also presented.

Germany, G. A.↗
NASA NTRS1999

Multi-Scale Fractal Analysis of Image Texture and Pattern

Analyses of the fractal dimension of Normalized Difference Vegetation Index (NDVI) images of homogeneous land covers near Huntsville, Alabama revealed that the fractal dimension of an image of an agricultural land cover indicates greater complexity as pixel size increases, a forested land cover gradually grows smoother, and an urban image remains roughly self-similar over the range of pixel sizes analyzed (10 to 80 meters). A similar analysis of Landsat Thematic Mapper images of the East Humboldt Range in Nevada taken four months apart show a more complex relation between pixel size and fractal dimension. The major visible difference between the spring and late summer NDVI images of the absence of high elevation snow cover in the summer image. This change significantly alters the relation between fractal dimension and pixel size. The slope of the fractal dimensional-resolution relation provides indications of how image classification or feature identification will be affected by changes in sensor spatial resolution.

Emerson, Charles W.↗
NASA NTRS1997

Compensation for Spherical Geometric and Absorption Effects on Lower Thermospheric Emission Intensities Derived from High Earth Orbit Images

Remote sensing of the atmosphere from high earth orbit is very attractive due to the large field of view obtained and a true global perspective. This viewpoint is complicated by earth curvature effects so that slant path enhancement and absorption effects, small from low earth orbit, become dominant even at small nadir view angles. The effect is further complicated by the large range of local times and solar zenith angles in a single image leading to a modulation of the image intensity by a significant portion of the diurnal height variation of the absorbing layer. The latter effect is significant in particular for mesospheric, stratospheric and auroral emissions due to their depth in the atmosphere. As a particular case, the emissions from atomic oxygen (130.4 and 135.6 nm) and molecular nitrogen (two LBH bands, LBHS from 140 to 160 nm and LBHL from 160 to 180 nm) as viewed from the Ultraviolet Imager (UVI) are examined. The LBH emissions are of particular interest since LBHS has significant 02 absorption while LBHL does not, In the case of auroral emissions this differential absorption, well examined in the nadir, gives information about the height of the emission and therefore the energy of the precipitating particles. Using simulations of the viewing geometry and images from the UVI we examine these effects and obtain correction factors to adjust to the nadir case with a significant improvement of the derived characteristic energy. There is a surprisingly large effect on the images from the 02 diurnal layer height changes. An empirical compensation to the nadir case is explored based on the local nadir and local zenith angles for each portion of the image. These compensations are demonstrated as applied to the above emissions in both auroral and dayglow images and compared to models. The extension of these findings to other instruments, emissions and spectral regions is examined.

Swift, W.↗
NASA NTRS1993

An Integrated Imaging Detector of Polarization and Spectral Content

A new type of image detector has been designed to simultaneously analyze the polarization of light at all picture elements in a scene. The Integrated Dual Imaging Detector (IDID) consists of a polarizing beamsplitter bonded to a charge-coupled device (CCD), with signal-analysis circuitry and analog-to-digital converters, all integrated on a silicon chip. It should be capable of 1:10(exp 4) polarization discrimination. The IDID should simplify the design and operation of imaging polarimeters and spectroscopic imagers used, for example, in atmospheric and solar research. Innovations in the IDID include (1) two interleaved 512 x 1024-pixel imaging arrays (one for each polarization plane); (2) large dynamic range (well depth of 10(exp 6) electrons per pixel); (3) simultaneous readout of both images at 10 million pixels per second each; (4) on-chip analog signal processing to produce polarization maps in real time; (5) on-chip 10-bit A/D conversion. When used with a lithium-niobate Fabry-Perot etalon or other color filter that can encode spectral information as polarization, the IDID can collect and analyze simultaneous images at two wavelengths. Precise photometric analysis of molecular or atomic concentrations in the atmosphere is one suggested application. When used in a solar telescope, the IDID will charge the polarization, which can then be converted to maps of the vector magnetic fields on the solar surface.

Rust, D. M.↗
NASA NTRS1995

A Compact Polarization Imager

A new type of image detector has been designed to analyze the polarization of light simultaneously at all picture elements (pixels) in a scene. The Integrated Dual Imaging Detector (IDID) consists of a polarizing beamsplitter bonded to a custom-designed charge-coupled device with signal-analysis circuitry, all integrated on a silicon chip. The IDID should simplify the design and operation of imaging polarimeters and spectroscopic imagers used, for example, in atmospheric and solar research. Other applications include environmental monitoring and robot vision. Innovations in the IDID include two interleaved 512 x 1024 pixel imaging arrays (one for each polarization plane), large dynamic range (well depth of 10(exp 6) electrons per pixel), simultaneous readout and display of both images at 10(exp 6) pixels per second, and on-chip analog signal processing to produce polarization maps in real time. When used with a lithium niobate Fabry-Perot etalon or other color filter that can encode spectral information as polarization, the IDID can reveal tiny differences between simultaneous images at two wavelengths.

Thompson, Karl E.↗
NASA NTRS1999

Multi-Scale Fractal Analysis of Image Texture and Pattern

Analyses of the fractal dimension of Normalized Difference Vegetation Index (NDVI) images of homogeneous land covers near Huntsville, Alabama revealed that the fractal dimension of an image of an agricultural land cover indicates greater complexity as pixel size increases, a forested land cover gradually grows smoother, and an urban image remains roughly self-similar over the range of pixel sizes analyzed (10 to 80 meters). A similar analysis of Landsat Thematic Mapper images of the East Humboldt Range in Nevada taken four months apart show a more complex relation between pixel size and fractal dimension. The major visible difference between the spring and late summer NDVI images is the absence of high elevation snow cover in the summer image. This change significantly alters the relation between fractal dimension and pixel size. The slope of the fractal dimension-resolution relation provides indications of how image classification or feature identification will be affected by changes in sensor spatial resolution.

Emerson, Charles W.↗
NASA NTRS1998

Study on Over-Sampling for Imager

This report describes the potential improvement of the effective ground resolution of MTSAT (Multi-functional Transport Satellite) Imager. The IFOV (Instantaneous Field of View) of MTSAT Imager is 4 km for infrared and 1 km visible. A combination of some images acquired by the MTSAT Imager could generate 2 km-latticed infrared images. Furthermore, it is possible to generate an effective 2 km IFOV image by the enhancement of the 2 km-latticed image using Digital Signal Processing. This report also mentions the on-orbit demonstration of this concept.

Kigawa, Seiichiro↗
NASA NTRS1999

Near-Infrared Hyperspectral Image Cubes of Mars during the 1999 Opposition

We used the Goddard Space Flight Center, Acousto-Optic Tunable Filter (AOTF) Camera to obtain near-IR spectral image sets of Mars over the 1.6-3.6 micron region during the April 1999 opposition. A complete image set consists of 280 images with a spectral full-width-half maximum of 10 wavenumbers (fixed in frequency), 90 images in H-band (1.55-1.80 micron), 115 images in K-band (1.95-2.50 micron) and 75 images in L-band (2.90-3.70 micron). The short-wavelength limit is set by transmission of AOTF cell and long-wavelength limit is imposed by sensitivity of PICNIC, 256x256, HgCdTe array detector. We will discuss the new array performance and provide preliminary interpretations of some of these results. These measurements were part of a 4-observatory coordinated effort whose overall objective was to assemble a photometrically calibrated, spectrally complete ground-based image cube over the visible and near-IR spectral region. To accomplish this, four observing teams conducted the investigations with instruments spanning 0.4 to 5.0 micron. The instruments and observing facilities were (a) AOTF camera at Apache Point Observatory, 3.5m, f/10, Nasymth focus (this abstract). Primary science targets included the 3 micron water-of hydration feature and CO2, H2O ice (polar regions and clouds); (b) Visible/NIR interference-filter (24 filters) camera at Lowell Observatory, 72" telescope. 430-1050 nm. Science targets were Fe(2+), Fe(3+) mineralogy and coarse grain hematite search; (c) NMSU Tortugas Mountain Observatory, 60 cm telescope, CCD photometry with same filter set as Lowell; (d) KPNO cryogenic grating/slit spectrometer (CRSP/SALLY) at KPNO 2.1 m, f/15 Cassegrain focus (see abstract by D. Glenar, et. al., this meeting). Selected wavelengths in 3-5 micron region (L, M band). Science targets included water-of-hydration feature (3-4 micron long wave extension) and sulfate mineralogy. Observers participating in this campaign included Dave Glenar, John Hillman, Gordon Bjoraker and Fred Espenak from GSFC, Nancy Chanover, Jim Murphy and A. S. MurTell from NMSU, Leslie Young from BU, Diana Blaney from JPL and Dick Joyce from KPNO.

Hillman, John J.↗
NASA NTRS1999

Ultraviolet, Optical and X-Ray Imaging of Selected Cygnus Loop Fields

During the Astro-1 and Astro-2 Space Shuttle missions in 1990 and 1995, far ultraviolet (FUV) images of five 40 ft diameter fields around the rim of the Cygnus Loop Super Nova Remnants (SNR) were observed with the Ultraviolet Imaging Telescope (UIT). These fields sample a broad range of SNR conditions including both radiative and non-radiative shocks in various geometries and scales. The UIT B5 band images discussed here sample predominantly ion-C4 lambda 1550 and the 2-photon continuum. Smaller contributions are made by emission lines of ion He-2 lambda 1640 and ion 03 lambda 1666. A unique aspect of the B5 band is its ability to sample the hydrogen 2-photon continuum from regions where the gas is recombining. We present these new FUV images and compare them with optical H-alpha and [ion O13], and ROSAT HRI X-ray images. In non-radiative shocks, existing 2-photon flux measurements from spectra and the H-alpha images suggest we are seeing approximately equal contributions from 2-photon and ion C4 emission. In radiative filaments, however, shock models and our images suggest ion C4 should dominate while spectra of specific locations seem to indicate that 2-photon emission dominates. We surmise that spectral observations on specific bright filaments have decreased locally-observed levels of ion C41 emission due to resonance scattering in that line.

Danforth, C. W.↗
NASA NTRS1999

Information-Theoretic Assessment of Sample Imaging Systems

By rigorously extending modern communication theory to the assessment of sampled imaging systems, we develop the formulations that are required to optimize the performance of these systems within the critical constraints of image gathering, data transmission, and image display. The goal of this optimization is to produce images with the best possible visual quality for the wide range of statistical properties of the radiance field of natural scenes that one normally encounters. Extensive computational results are presented to assess the performance of sampled imaging systems in terms of information rate, theoretical minimum data rate, and fidelity. Comparisons of this assessment with perceptual and measurable performance demonstrate that (1) the information rate that a sampled imaging system conveys from the captured radiance field to the observer is closely correlated with the fidelity, sharpness and clarity with which the observed images can be restored and (2) the associated theoretical minimum data rate is closely correlated with the lowest data rate with which the acquired signal can be encoded for efficient transmission.

Huck, Friedrich O.↗
NASA NTRS2000

BOREAS RSS-7 Landsat TM LAI IMages of the SSA and NSA

The BOReal Ecosystem-Atmosphere Study Remote Sensing Science (BOREAS RSS-7) team used Landsat Thematic Mapper (TM) images processed at CCRS to produce images of Leaf Area Index (LAI) for the BOREAS study areas. Two images acquired on 06-Jun and 09-Aug-1991 were used for the SSA, and one image acquired on 09-Jun-1994 was used for the NSA. The LAI images are based on ground measurements and Landsat TM Reduced Simple Ratio (RSR) images. The data are stored in binary image-format files.

Hall, Forrest G.↗
NASA NTRS2001

Retrieval of Temperature and Species Distributions from Multispectral Image Data of Surface Flame Spread in Microgravity

Weight, size, and power constraints severely limit the ability of researchers to fully characterize temperature and species distributions in microgravity combustion experiments. A powerful diagnostic technique, infrared imaging spectrometry, has the potential to address the need for temperature and species distribution measurements in microgravity experiments. An infrared spectrum imaged along a line-of-sight contains information on the temperature and species distribution in the imaged path. With multiple lines-of-sight and approximate knowledge of the geometry of the combustion flowfield, a three-dimensional distribution of temperature and species can be obtained from one hyperspectral image of a flame. While infrared imaging spectrometers exist for collecting hyperspectral imagery, the remaining challenge is retrieving the temperature and species information from this data. An initial version of an infrared analysis software package, called CAMEO (Combustion Analysis Model et Optimizer), has been developed for retrieving temperature and species distributions from hyperspectral imaging data of combustion flowfields. CAMEO has been applied to the analysis of multispectral imaging data of flame spread over a PMMA surface in microgravity that was acquired in the DARTFire program. In the next section of this paper, a description of CAMEO and its operation is presented, followed by the results of the analysis of microgravity flame spread data.

Annen, K. D.↗
NASA NTRS2001

Demonstration of Imaging Fourier Transform Spectrometer (FTS) Performance for Planetary and Geostationary Earth Observing

The combination of massively parallel spatial sampling and accurate spectral radiometry offered by imaging FTS makes it extremely attractive for earth and planetary remote sensing. We constructed a breadboard instrument to help assess the potential for planetary applications of small imaging FTS instruments in the 1 - 5 micrometer range. The results also support definition of the NASA Geostationary Imaging FTS (GIFTS) instrument that will make key meteorological and climate observations from geostationary earth orbit. The Planetary Imaging FTS (PIFTS) breadboard is based on a custom miniaturized Bomen interferometer that uses corner cube reflectors, a wishbone pivoting voice-coil delay scan mechanism, and a laser diode metrology system. The interferometer optical output is measured by a commercial infrared camera procured from Santa Barbara Focalplane. It uses an InSb 128x128 detector array that covers the entire FOV of the instrument when coupled with a 25 mm focal length commercial camera lens. With appropriate lenses and cold filters the instrument can be used from the visible to 5 micrometers. The delay scan is continuous, but slow, covering the maximum range of +/- 0.4 cm in 37.56 sec at a rate of 500 image frames per second. Image exposures are timed to be centered around predicted zero crossings. The design allows for prediction algorithms that account for the most recent fringe rate so that timing jitter produced by scan speed variations can be minimized. Response to a fixed source is linear with exposure time nearly to the point of saturation. Linearity with respect to input variations was demonstrated to within 0.16% using a 3-point blackbody calibration. Imaging of external complex scenes was carried out at low and high spectral resolution. These require full complex calibration to remove background contributions that vary dramatically over the instrument FOV. Testing is continuing to demonstrate the precise radiometric accuracy and noise characteristics.

Revercomb, Henry E.↗
NASA NTRS1994

Nonlinear Optical Image Processing with Bacteriorhodopsin Films

The transmission properties of some bacteriorhodopsin film spatial light modulators are uniquely suited to allow nonlinear optical image processing operations to be applied to images with multiplicative noise characteristics. A logarithmic amplitude transmission feature of the film permits the conversion of multiplicative noise to additive noise, which may then be linearly filtered out in the Fourier plane of the transformed image. The bacteriorhodopsin film displays the logarithmic amplitude response for write beam intensities spanning a dynamic range greater than 2.0 orders of magnitude. We present experimental results demonstrating the principle and capability for several different image and noise situations, including deterministic noise and speckle. Using the bacteriorhodopsin film, we successfully filter out image noise from the transformed image that cannot be removed from the original image.

Downie, John D.↗
NASA NTRS1994

Optical Processing of Speckle Images with Bacteriorhodopsin for Pattern Recognition

Logarithmic processing of images with multiplicative noise characteristics can be utilized to transform the image into one with an additive noise distribution. This simplifies subsequent image processing steps for applications such as image restoration or correlation for pattern recognition. One particularly common form of multiplicative noise is speckle, for which the logarithmic operation not only produces additive noise, but also makes it of constant variance (signal-independent). We examine the optical transmission properties of some bacteriorhodopsin films here and find them well suited to implement such a pointwise logarithmic transformation optically in a parallel fashion. We present experimental results of the optical conversion of speckle images into transformed images with additive, signal-independent noise statistics using the real-time photochromic properties of bacteriorhodopsin. We provide an example of improved correlation performance in terms of correlation peak signal-to-noise for such a transformed speckle image.

Downie, John D.↗
NASA NTRS2001

Hyperspectral Imaging and Spectroscopy of Fluorescently Coupled Acyl-CoA: Cholesterol Acyltransferase in Insect Cells

A high-performance hyperspectral imaging module with high throughput of light suitable for low-intensity fluorescence microscopic imaging and subsequent analysis, including single-pixel-defined emission spectroscopy, was tested on Sf21 insect cells expressing green fluorescence associated with recombinant green fluorescent protein linked or not with the membrane protein acyl-CoA:cholesterol acyltransferase. The imager utilized the phenomenon of optical activity as a new technique providing information over a spectral range of 220-1400 nm, and was inserted between the microscope and an 8-bit CCD video-rate camera. The resulting fluorescence image did not introduce observable image aberrations. The images provided parallel acquisition of well resolved concurrent spatial and spectral information such that fluorescence associated with green fluorescent protein alone was demonstrated to be diffuse within the Sf21 insect cell, and that green fluorescence associated with the membrane protein was shown to be specifically concentrated within regions of the cell cytoplasm. Emission spectra analyzed from different regions of the fluorescence image showed blue shift specific for the regions of concentration associated with the membrane protein.

Malak, H.↗