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NASA NTRS1991

Progressive transmission of pseudo-color images. Appendix 1: Item 4

The transmission of digital images can require considerable channel bandwidth. The cost of obtaining such a channel can be prohibitive, or the channel might simply not be available. In this case, progressive transmission (PT) can be useful. PT presents the user with a coarse initial image approximation, and then proceeds to refine it. In this way, the user tends to receive information about the content of the image sooner than if a sequential transmission method is used. PT finds application in image data base browsing, teleconferencing, medical and other applications. A PT scheme is developed for use with a particular type of image data, the pseudo-color or color mapped image. Such images consist of a table of colors called a colormap, plus a 2-D array of index values which indicate which colormap entry is to be used to display a given pixel. This type of image presents some unique problems for a PT coder, and techniques for overcoming these problems are developed. A computer simulation of the color mapped PT scheme is developed to evaluate its performance. Results of simulation using several test images are presented.

Hadenfeldt, Andrew C.↗

NASA NTRS1991

Parameter trade-offs for imaging spectroscopy systems

With the advent of the EOS era and of configurable sensors, users of these instruments are faced with the twin problems of specifying data acquisition parameters and extracting desired information from the voluminous data. An application of a system model is made to explore system parameter trade-offs for a model sensor based on the High Resolution Imaging Spectrometer. Radiometric performance was studied, along with the effect on classification accuracy of several system parameters. Using a model scene based on typical agricultural reflectance and atmospheric conditions, the atmosphere and sensor are seen to have significant effects on the mean received signal and noise performance. The effect of random uncorrelated errors in the radiometric calibration of the detector array is seen to degrade system performance, especially in the spectral bands below 1 micron. Accurate pixel-to-pixel relative radiometric calibration and the use of the Image Motion Compensation option are seen to improve classification accuracy, especially at high solar zenith angles. Feature sets chosen from characteristics of the scene performed best overall, but ones chosen based on signal-to-noise ratios were seen to be more robust.

Kerekes, John P.↗

NASA NTRS1994

Uncooled tunneling infrared sensor

An uncooled infrared tunneling sensor in which the only moving part is a diaphragm which is deflected into contact with a micromachined silicon tip electrode prepared by a novel lithographic process. Similarly prepared deflection electrodes employ electrostatic force to control the deflection of a silicon nitride, flat diaphragm membrane. The diaphragm exhibits a high resonant frequency which reduces the sensor's sensitivity to vibration. A high bandwidth feedback circuit controls the tunneling current by adjusting the deflection voltage to maintain a constant deflection of the membrane which would otherwise change deflection depending upon incident infrared radiation. The resulting infrared sensor will meet or exceed the performance of all other broadband, uncooled, infrared sensors and can be miniaturized to pixel dimensions smaller than 100 .mu.m. The technology is readily implemented as a small-format linear array suitable for commercial and spacecraft applications.

Kenny, Thomas W.↗

NASA NTRS1991

Optical correlator method and apparatus for particle image velocimetry processing

Young's fringes are produced from a double exposure image of particles in a flowing fluid by passing laser light through the film and projecting the light onto a screen. A video camera receives the image from the screen and controls a spatial light modulator. The spatial modulator has a two dimensional array of cells the transmissiveness of which are controlled in relation to the brightness of the corresponding pixel of the video camera image of the screen. A collimated beam of laser light is passed through the spatial light modulator to produce a diffraction pattern which is focused onto another video camera, with the output of the camera being digitized and provided to a microcomputer. The diffraction pattern formed when the laser light is passed through the spatial light modulator and is focused to a point corresponds to the two dimensional Fourier transform of the Young's fringe pattern projected onto the screen. The data obtained fro This invention was made with U.S. Government support awarded by the Department of the Army (DOD) and NASA grand number(s): DOD #DAAL03-86-K0174 and NASA #NAG3-718. The U.S. Government has certain rights in this invention.

Farrell, Patrick V.↗

NASA NTRS2010

Phenological Parameters Estimation Tool

The Phenological Parameters Estimation Tool (PPET) is a set of algorithms implemented in MATLAB that estimates key vegetative phenological parameters. For a given year, the PPET software package takes in temporally processed vegetation index data (3D spatio-temporal arrays) generated by the time series product tool (TSPT) and outputs spatial grids (2D arrays) of vegetation phenological parameters. As a precursor to PPET, the TSPT uses quality information for each pixel of each date to remove bad or suspect data, and then interpolates and digitally fills data voids in the time series to produce a continuous, smoothed vegetation index product. During processing, the TSPT displays NDVI (Normalized Difference Vegetation Index) time series plots and images from the temporally processed pixels. Both the TSPT and PPET currently use moderate resolution imaging spectroradiometer (MODIS) satellite multispectral data as a default, but each software package is modifiable and could be used with any high-temporal-rate remote sensing data collection system that is capable of producing vegetation indices. Raw MODIS data from the Aqua and Terra satellites is processed using the TSPT to generate a filtered time series data product. The PPET then uses the TSPT output to generate phenological parameters for desired locations. PPET output data tiles are mosaicked into a Conterminous United States (CONUS) data layer using ERDAS IMAGINE, or equivalent software package. Mosaics of the vegetation phenology data products are then reprojected to the desired map projection using ERDAS IMAGINE

McKellip, Rodney D.↗

NASA NTRS2002

Superconducting kinetic inductance photon detectors.

We are investigating a novel superconducting detector and readout method that could lead to photon counting, energy resolving focal plane arrays. This concept is intrinsically different from STJ and TES detectors, and in principle could deliver large pixel counts, high sensitivity, and Fano-limited spectral resolution in the ptical/UV/X-ray bands. The readout uses the monotonic relation between the kinetic surface inductance L***subs***, of a superconductor and the density of quasiparticles n, which holds even at temperatures far below T***subc***. This allows a sensitive readout of the number of excess quasiparticles in the detector by monitoring the transmission phase of a resonant circuit. The most intriguing aspect of this concept is that passive frequency multiplexing could be used to read out ~ l0***super4*** detectors with a single HEMT amplifier. Single x-ray events have been observed in prototype detectors.

kinetic↗

NASA NTRSDate not supplied

Toward Large Field-of-view X-ray Spectrometers with Magnetic Microcalorimeters

A future X-ray telescope mission like Lynx, a X-ray flagship mission concept, requires a large field of view, high energy resolution, and high spatial resolution. The Magnetic Microcalorimeter (MMC) detectors we are developing for such a mission feature a 5-arcminute field of view, approximately 100,000 pixels, each spanning 0.5–1 arcsecond. These detectors require the readout of 8,000 sensors. Three different array types have been designed to meet scientific goals, two of which utilize thermal multiplexing to reduce the number of readout channels in a scheme called “Hydra.” We are currently fabricating detectors on a recently completed buried wiring wafer with connections to every sensor. The sensors are read out using a microwave multiplexer (μMUX) with flux ramp modulation. A single μMUX can read out approximately 1,000 sensors with only two feed lines. We will report on the test of the first two-dimensional μMUX chip, consisting of 78 resonators. μMUX chips that pass screening will be directly bonded to MMC array chips using indium bump bonding. In parallel, we have tested a kinetic inductance traveling wave parametric amplifier (KI-TWPA) to amplify signals at low temperatures. The KI-TWPA exhibits extremely low internal noise, approaching the standard quantum limit. Since the energy resolution of an MMC is primarily limited by the readout system, the KI-TWPA is an ideal amplifier for MMCs with μMUX readout. We recently measured the readout noise of a μMUX with a KI-TWPA, demonstrating its capability for reading out MMC arrays. We present the design and fabrication of the latest MMC detectors, along with its readout performance.

Magntic Microcalorimeters↗

NASA NTRS2011

Integrated Arrays on Silicon at Terahertz Frequencies

In this paper we explore various receiver font-end and antenna architecture for use in integrated arrays at terahertz frequencies. Development of wafer-level integrated terahertz receiver front-end by using advanced semiconductor fabrication technologies and use of novel integrated antennas with silicon micromachining are reported. We report novel stacking of micromachined silicon wafers which allows for the 3-dimensional integration of various terahertz receiver components in extremely small packages which easily leads to the development of 2- dimensioanl multi-pixel receiver front-ends in the terahertz frequency range. We also report an integrated micro-lens antenna that goes with the silicon micro-machined front-end. The micro-lens antenna is fed by a waveguide that excites a silicon lens antenna through a leaky-wave or electromagnetic band gap (EBG) resonant cavity. We utilized advanced semiconductor nanofabrication techniques to design, fabricate, and demonstrate a super-compact, low-mass submillimeter-wave heterodyne frontend. When the micro-lens antenna is integrated with the receiver front-end we will be able to assemble integrated heterodyne array receivers for various applications such as multi-pixel high resolution spectrometer and imaging radar at terahertz frequencies.

silicon micromaching↗

NASA NTRS1996

The South Pole Imaging Fabry Perot Interferometer (SPIFI)

The design and construction of the South Pole imaging Fabry-Perot interferometer (SPIFI) is reported. The SPIFI is a direct detection imaging spectrometer for use in the far infrared and submillimeter bands accessible to the 1.7 m telescope at the South Pole, and in the submillimeter bands accessible to the 15 m James Clerk Maxwell Telescope (JCMT), HI. It employs a 5 x 5 silicon bolometer array and three cryogenic Fabry Perot interferometers in series in order to achieve velocity resolutions of between 300 km/s and 30 km/s over the entire field of view with a resolution of up to 1 km/s at the center pixel. The scientific justification for the instrument is discussed, considering the spectral lines available to SPIFI. The optical path, the cryogenic Fabry-Perot, the adiabatic demagnetization refrigerator and the detector array are described. The instrument's sensitivity is presented and compared with coherent systems.

Stacey, G. J.↗

NASA NTRS1989

Performance of the image statistics decoder in conjunction with the Goldstone-VLA array

During Voyager's Neptune encounter, the National Radio Astronomy Observatory's Very Large Array (VLA) will be arrayed with Goldstone antennas to receive the transmitted telemetry data from the spacecraft. The telemetry signal from the VLA will drop out periodically, resulting in a periodic drop in the received signal-to-noise ratio (SNR). The Image Statistics Decoder (ISD), which assumes a correlation between pixels, can improve the bit error rate (BER) for images during these dropout periods. Simulation results have shown that the ISD, in conjunction with the Goldstone-VLA array can provide a 3-dB gain for uncompressed images at a BER of 5.0 x 10(exp -3).

Wang, H. C.↗

NASA NTRS2010

FPGA Coprocessor Design for an Onboard Multi-Angle Spectro-Polarimetric Imager

A multi-angle spectro-polarimetric imager (MSPI) is an advanced camera system currently under development at JPL for possible future consideration on a satellite-based Aerosol-Cloud-Environ - ment (ACE) interaction study. The light in the optical system is subjected to a complex modulation designed to make the overall system robust against many instrumental artifacts that have plagued such measurements in the past. This scheme involves two photoelastic modulators that are beating in a carefully selected pattern against each other. In order to properly sample this modulation pattern, each of the proposed nine cameras in the system needs to read out its imager array about 1,000 times per second. The onboard processing required to compress this data involves least-squares fits (LSFs) of Bessel functions to data from every pixel in realtime, thus requiring an onboard computing system with advanced data processing capabilities in excess of those commonly available for space flight. As a potential solution to meet the MSPI onboard processing requirements, an LSF algorithm was developed on the Xilinx Virtex-4FX60 field programmable gate array (FPGA). In addition to configurable hardware capability, this FPGA includes Power -PC405 microprocessors, which together enable a combination hardware/ software processing system. A laboratory demonstration was carried out based on a hardware/ software co-designed processing architecture that includes hardware-based data collection and least-squares fitting (computationally), and softwarebased transcendental function computation (algorithmically complex) on the FPGA. Initial results showed that these calculations can be handled using a combination of the Virtex- 4TM Power-PC core and the hardware fabric.

Pingree, Paula J.↗

NASA NTRS2008

Model of Image Artifacts from Dust Particles

A mathematical model of image artifacts produced by dust particles on lenses has been derived. Machine-vision systems often have to work with camera lenses that become dusty during use. Dust particles on the front surface of a lens produce image artifacts that can potentially affect the performance of a machine-vision algorithm. The present model satisfies a need for a means of synthesizing dust image artifacts for testing machine-vision algorithms for robustness (or the lack thereof) in the presence of dust on lenses. A dust particle can absorb light or scatter light out of some pixels, thereby giving rise to a dark dust artifact. It can also scatter light into other pixels, thereby giving rise to a bright dust artifact. For the sake of simplicity, this model deals only with dark dust artifacts. The model effectively represents dark dust artifacts as an attenuation image consisting of an array of diffuse darkened spots centered at image locations corresponding to the locations of dust particles. The dust artifacts are computationally incorporated into a given test image by simply multiplying the brightness value of each pixel by a transmission factor that incorporates the factor of attenuation, by dust particles, of the light incident on that pixel. With respect to computation of the attenuation and transmission factors, the model is based on a first-order geometric (ray)-optics treatment of the shadows cast by dust particles on the image detector. In this model, the light collected by a pixel is deemed to be confined to a pair of cones defined by the location of the pixel s image in object space, the entrance pupil of the lens, and the location of the pixel in the image plane (see Figure 1). For simplicity, it is assumed that the size of a dust particle is somewhat less than the diameter, at the front surface of the lens, of any collection cone containing all or part of that dust particle. Under this assumption, the shape of any individual dust particle artifact is the shape (typically, circular) of the aperture, and the contribution of the particle to the attenuation factor for a given pixel is the fraction of the cross-sectional area of the collection cone occupied by the particle. Assuming that dust particles do not overlap, the net transmission factor for a given pixel is calculated as one minus the sum of attenuation factors contributed by all dust particles affecting that pixel. In a test, the model was used to synthesize attenuation images for random distributions of dust particles on the front surface of a lens at various relative aperture (F-number) settings. As shown in Figure 2, the attenuation images resembled dust artifacts in real test images recorded while the lens was aimed at a white target.

Willson, Reg↗

NASA NTRS2017

Design and Optimization of Multi-Pixel Transition-Edge Sensors for X-Ray Astronomy Applications

Multi-pixel transition-edge sensors (TESs), commonly referred to as 'hydras', are a type of position sensitive micro-calorimeter that enables very large format arrays to be designed without commensurate increase in the number of readout channels and associated wiring. In the hydra design, a single TES is coupled to discrete absorbers via varied thermal links. The links act as low pass thermal filters that are tuned to give a different characteristic pulse shape for x-ray photons absorbed in each of the hydra sub pixels. In this contribution we report on the experimental results from hydras consisting of up to 20 pixels per TES. We discuss the design trade-offs between energy resolution, position discrimination and number of pixels and investigate future design optimizations specifically targeted at meeting the readout technology considered for Lynx.

Smith, Stephen J.↗

DOE OSTI2024

Hierarchical Phased-Array Antennas Coupled to Al KIDs: A Scalable Architecture for Multi-band Millimeter/Submillimeter Focal Planes

We present the optical characterization of two-scale hierarchical phased-array antenna kinetic inductance detectors (KIDs) for millimeter/submillimeter wavelengths. Our KIDs have a lumped-element architecture with parallel plate capacitors and aluminum inductors. The incoming light is received with a hierarchical phased array of slot dipole antennas, split into 4 frequency bands (between 125 GHz and 365 GHz) with on-chip lumped-element band-pass filters, and routed to different KIDs using microstriplines. Individual pixels detect light for the 3 higher-frequency bands (190–365 GHz), and the signals from four individual pixels are coherently summed to create a larger pixel detecting light for the lowest frequency band (125–175 GHz). The spectral response of the band-pass filters was measured using Fourier transform spectroscopy (FTS), the far-field beam pattern of the phased-array antennas was obtained using an infrared source mounted on a 2-axis translating stage, and the optical efficiency of the KIDs was characterized by observing loads at 294 K and 77 K. We report on the results of these three measurements.

47 OTHER INSTRUMENTATION↗

NASA NTRS1990

Evaluation of the airborne visible-infrared imaging spectrometer for mapping subtle lithological variation

The Airborne Visible/Infrared Imaging Spectrometer (AVIRIS), flown aboard the NASA ER-2 aircraft in 1987 and 1989, used four linear arrays and four individual spectrometers to collect data simultaneously from the 224 bands in a scanned 614 pixel-wide swath perpendicular to the aircraft direction. The research had two goals. One was to evaluate the AVIRIS data. The other was to look at the subtle lithological variation at the two test sites to develop a better understanding of the regional geology and surficial processes. The geometric characteristics of the data, adequacy of the spatial resolution, and adequacy of the spectral sampling interval are evaluated. Geologic differences at the test sites were mapped. They included lithological variation caused by primary sedimentary layering, facies variation, and weathering; and subtle mineralogical differences caused by hydrothermal alterations of igneous and sedimentary rocks. The investigation used laboratory, field, and aircraft spectral measurements; known properties of geological materials; digital image processing and spectrum processing techniques; and field geologic data to evaluate the selected characteristics of the AVIRIS data.

Kruse, Fred A.↗

NASA NTRS1996

High-Speed Binary-Output Image Sensor

Photodetector outputs digitized by circuitry on same integrated-circuit chip. Developmental special-purpose binary-output image sensor designed to capture up to 1,000 images per second, with resolution greater than 10 to the 6th power pixels per image. Lower-resolution but higher-frame-rate prototype of sensor contains 128 x 128 array of photodiodes on complementary metal oxide/semiconductor (CMOS) integrated-circuit chip. In application for which it is being developed, sensor used to examine helicopter oil to determine whether amount of metal and sand in oil sufficient to warrant replacement.

Fossum, Eric↗

NASA NTRS1996

CMOS Active-Pixel Image Sensor With Simple Floating Gates

Experimental complementary metal-oxide/semiconductor (CMOS) active-pixel image sensor integrated circuit features simple floating-gate structure, with metal-oxide/semiconductor field-effect transistor (MOSFET) as active circuit element in each pixel. Provides flexibility of readout modes, no kTC noise, and relatively simple structure suitable for high-density arrays. Features desirable for "smart sensor" applications.

Fossum, Eric R.↗

NASA NTRS1999

Integrated Dual Imaging Detector

A new type of image detector was designed to simultaneously analyze the polarization of light at all picture elements in a scene. The integrated Dual Imaging detector (IDID) consists of a lenslet array and a polarizing beamsplitter bonded to a commercial charge coupled device (CCD). The IDID simplifies the design and operation of solar vector magnetographs and the imaging polarimeters and spectroscopic imagers used, for example, in atmosphere and solar research. When used in a solar telescope, the vector magnetic fields on the solar surface. Other applications include environmental monitoring, robot vision, and medical diagnoses (through the eye). Innovations in the IDID include (1) two interleaved imaging arrays (one for each polarization plane); (2) large dynamic range (well depth of 10(exp 5) electrons per pixel); (3) simultaneous readout and display of both images; and (4) laptop computer signal processing to produce polarization maps in field situations.

Rust, David M.↗