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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 865 records · Page 48

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NASA NTRS1988

Status of direct detector and array development

Programs are now underway to develop and demonstrate the detector/array technology needed for the Space Infrared Telescope Facility (SIRTF), Large Deployable Reflector (LDR), and other future NASA missions. The development goal is to achieve focal plane sensitivities, at extended integration times over the 2 to 700 microns range, limited only by the low astrophysical backgrounds encountered in cryogenic telescopes such as SIRTF. Dramatic progress has been made in the last 2 to 3 years in integrated array and detector systems for low background astronomical applications. With the broadly based developments and lab characterizations now underway for SIRTF and similar space applications, coupled with the rapidly expanding art and science of ground based astronomical imagery with arrays, the potential for effective utilization of arrays with LDR appears to be very good.

Mccreight, Craig R.↗

NASA NTRS1989

A space qualified thermal imaging system using a Pt Si detector array

EDO Corporation, Barnes Engineering Division designed and constructed a high resolution thermal imaging system on contract to Lockheed for use in the SDI Star Lab. This employs a Pt Si CCD array which is sensitive in the spectral range of 3 to 5 microns. Star Lab will be flown in the Shuttle bay and consists basically of a large, reflecting, tracking telescope with associated sensors and electronics. The thermal imaging system is designed to operate in the focal plane of this telescope. The configuration of the system is illustrated. The telescope provides a collimated beam output which is focussed onto the detector array by a silicon objective lens. The detector array subtends a field of view of 1.6 degrees x 1.22 degrees. A beam switching mirror permits bypassing the large telescope to give a field of 4 degrees x 3 degrees. Two 8 position filter wheels are provided, and background radiation is minimized by Narcissus mirrors. The detector is cooled with a Joule-Thompson cryostat fed from a high pressure supply tank. This was selected instead of a more convenient closed-cycle system because of concern with vibration. The latter may couple into the extremely critical Starlab tracking telescope. The electronics produce a digitized video signal for recording. Offset and responsivity correction factors are stored for all pixels and these corrections are made to the digitized output in real time.

Astheimer, Robert W.↗

NASA NTRS2011

Scanning and Defocusing Properties of Microstrip Reflectarray Antennas

A symmetric reflectarray, consisting of variable-size square patch elements with a commonly used mathematical model for the horn in the form of a cosine function, has been designed using the transmit mode technique for different f/D ratios with 10 dB edge taper. Subsequently, the antennas were analyzed for the radiation pattern and gain. The infinite array model was used to determine the reflection phase of each patch element in the design and analysis codes. By displacing the feed laterally, the scan characteristics were obtained, such as the beam deviation factor, gain loss, and pattern degradation. The properties of reflect arrays were compared to those of the conventional paraboloidal reflectors. The same procedure was used to study the scan properties of offset reflectarrays. There is no cross-polarized radiation in the principal planes for a symmetric system. Cross-polarized radiation exists in non-principal planes off broadside in symmetric systems, with greater levels for larger values of subtended angles. Such cross-polarized radiation level increases with subtended angle just as cross-polarization level increases with decreasing values of f/D ratios for symmetric paraboloids in non-principal planes. Pattern distortions and gain loss were found to be more severe in the case of a microstrip reflectarray compared to the conventional parabolic reflector. The scan performance of the reflect arrays was found to improve with f/D ratios as is true for paraboloids. In general, scanning by means of displaced feed is limited to a few beam - widths in reflectarrays. Feed displacement in the axial direction of a symmetric reflectarray was investigated and compared to that of paraboloids. The gain loss due to the defocused feed of a reflectarray was found to be nearly the same as that of a paraboloid of the same subtended angle for larger values of f/D, and for displacements away from the antenna. The gain loss of an axially defocused reflectarray was found to be greater than that of a paraboloid for displacements closer to the antenna, especially for smaller values of f/D. In general, the performance of a defocused reflectarray was found to be poorer than that of a comparable paraboloid reflector.

Rengarajan, Sembiam↗

NASA NTRS1974

Development of a long wavelength spectrometer for the 24-channel multispectral scanner: Instructions for installation, start-up, and adjustment

The basic information is presented, which is required for start-up and operation of two long-wavelength focal-plane and cooler assemblies, including the amplifiers and temperature control systems. The focal plane systems, referred to as the long wavelength spectrometer (LWS) were developed for direct replacement of Arrays 3 and 4 into the multispectral scanner presently being operated by the NASA Manned Spacecraft Center Facility, and Laboratory Support Branch. The equipment is comprised of two major sub-assemblies: Array 3 with three indium antimonide detector channels and Array 4 with seven mercury doped Germanium detector channels. Each array is mounted on a cryogenic cooler and includes the vacuum housings, mounting hardware (x, y, z translation and rotation stages) and detector signal conditioning, temperature control and monitoring electronics. The two arrays were designed to operate independently and do not share common equipment (viz power supplies, housings, mounts, etc.).

Source record↗

NASA NTRS1982

Beyond the supercomputer

A NASA-directed development of massively parallel processor (MPP) computers is outlined, noting intended applications for data processing for near term earth resource and environment mapping, radar, and television transmissions. The MPP is designed to perform 100 billion operations/sec to obtain satisfactory image processing, while separate processing units correct distortions, register images, calculate correlation functions, and classify multispectral characteristics. Arrays of 1s and 0s will be manipulated in analog-to-digital conversions generating separate planes corresponding to powers of binaries. Data wires are replaced by fiber-optic tubes or thousands of wires, and single logic gates are replaced by thousands of logic gates and every memory element by thousands of memory elements. Features of the interconnections and the images control processor units are detailed, along with implementation of sliders for program flexibility.

Schaefer, D. H.↗

NASA NTRS1989

Design and performance analysis of the CLAES Ne/CO2 cryostat

The design of the dual-stage Ne/CO2 cryostat, constructed for the Cryogenic Limb Array Etalon Spectrometer (CLAES) for the cooling, to their respective required operation temperatures, of the focal plane (to less than 15 K), spectrometer (to less than 30 K), telescope (to less than 150 K), and baffles (to less than 180 K) is described, and the cryostat's performance is analyzed. The results of this study show that the current cryostat will meet all sensor cooling requirements. The cryostat weighs 2276 lbs, of which 988 lbs are charged to the neon and 484 lbs are charged to the CO2. Schematic diagrams of the CLAES cooler/sensor and of the external plumbing are presented together with the test data.

Naes, L. G.↗

NASA NTRS1989

Development of a normal incidence multilayer, imaging X-ray microscope

This paper describes the design, analysis, and fabrication of a normal-incidence multilayer 20x Schwarzschild imaging X-ray microscope. The microscope is being fabricated using much of the technology implemented in the Multispectral Solar Telescope Array. Results of diffraction analysis show that better than 400 A spatial resolution in the object plane up to a 1-mm field of view can be achieved with 125 A radiation. Other microscope systems for use in conjunction with X-ray telescopes are analyzed and designed.

Shealy, David L.↗

NASA NTRS2010

A Framework for Propagation of Uncertainties in the Kepler Data Analysis Pipeline

The Kepler space telescope is designed to detect Earth-like planets around Sun-like stars using transit photometry by simultaneously observing 100,000 stellar targets nearly continuously over a three and a half year period. The 96-megapixel focal plane consists of 42 charge-coupled devices (CCD) each containing two 1024 x 1100 pixel arrays. Cross-correlations between calibrated pixels are introduced by common calibrations performed on each CCD requiring downstream data products access to the calibrated pixel covariance matrix in order to properly estimate uncertainties. The prohibitively large covariance matrices corresponding to the ~75,000 calibrated pixels per CCD preclude calculating and storing the covariance in standard lock-step fashion. We present a novel framework used to implement standard propagation of uncertainties (POU) in the Kepler Science Operations Center (SOC) data processing pipeline. The POU framework captures the variance of the raw pixel data and the kernel of each subsequent calibration transformation allowing the full covariance matrix of any subset of calibrated pixels to be recalled on-the-fly at any step in the calibration process. Singular value decomposition (SVD) is used to compress and low-pass filter the raw uncertainty data as well as any data dependent kernels. The combination of POU framework and SVD compression provide downstream consumers of the calibrated pixel data access to the full covariance matrix of any subset of the calibrated pixels traceable to pixel level measurement uncertainties without having to store, retrieve and operate on prohibitively large covariance matrices. We describe the POU Framework and SVD compression scheme and its implementation in the Kepler SOC pipeline.

Clarke, Bruce D.↗

NASA NTRS2011

Evaluation of the Reflection Coefficient of Microstrip Elements for Reflectarray Antennas

Basis functions were studied and identified that provide efficient and accurate solutions for the induced patch currents and the reflection phase in microstrip reflect arrays. The integral equation of an infinite array of microstrip elements in the form of patches or crossed dipoles excited by a uniform plane wave is solved by the method-of-moments. Efficient choices of entire domain basis functions that yield accurate results have been described.

Rengarajan, Sembiam↗

NASA NTRS1992

A radiation-hard, low-background multiplexer design for spacecraft imager applications

A possible multiplexer design for the focal plane for the Cassini Visible and Infrared Mapping Spectrometer (VIMS) is reviewed. The instrument's requirements for the multiplexed array are summarized. The VIMS instrument has a modest radiation-hardness requirement due to the trajectory and planetary environments in which the instrument will be required to operate. The total ionizing dose hardness requirement is a few tens of kilorads. A thin-gate oxide of a few hundred angstroms thickness is to be used. Field hardness is to be achieved by guard bands or hardened dielectric isolation. The design is argued to meet the low-noise and radiation-hardness required for imaging at Saturn. The design is versatile enough to provide double-correlated and double-uncorrelated sampling, which is accomplished in the signal processing electronics outside the focal plane.

Staller, Craig↗

NASA NTRS2019

Swirl Distortion Using Stream Vanes for Boundary Layer Ingestion Research

The swirl distortion of a StreamVane (Trademark) was investigated in the NASA Glenn Research Center W8 test facility. The StreamVane (Trademark) was designed and generated by Virginia Tech based on CFD simulations and included a center body at the aerodynamic interface plane. The swirl pattern generated by the distortion was evaluated using a dense grid of 5-hole Pitot probe measurements captured using a rotating array of probes. Good agreement was found between the design intent and the results at 38.5 kg/s mass flow. The StreamVane (Trademark) swirl results were compared to clean facility flow at 5 inlet mass flows and found to be consistent. Additionally, the axial location of the StreamVane (Trademark) relative to the measurement plane was investigated to determine the impact on downstream total pressure loss generated by the vanes. The intent of this work was to assess the viability of using a StreamVane (Trademark) to generate a Type I or Type II distortion into a Boundary Layer Ingesting propulsor to assess its aerodynamic performance and aeromechanic response.

swirl distortion↗

NASA NTRSDate not supplied

Insertion Loss of a Multi-Plane Light Conversion Device with Few Mode Fiber Outputs Under Atmospheric Conditions

A key challenge of photon counting optical communication is delivering light with atmospherically distorted wavefronts from the telescope to detectors efficiently. When using fiber coupled single photon detectors, the efficiency of the transmittance is constrained by the modes supported by the fiber. The number of modes supported by a fiber depends on the size of the core. The larger the core, the more modes supported. However, commercial off the shelf superconducting nanowire single photon detectors (SNSPDs) are currently limited in area, which limits the core size of the fibers that can efficiently couple to the detectors. To increase the amount of light that can be delivered to the detectors, NASA Glenn Research Center is considering many different fiber/detector architectures. This paper compares insertion loss of the fiber device for two different architectures: • a multi-plane light conversion device to split the light from a 30 µm core diameter fiber into 7 separate, 15 µm core diameter few-mode fibers butt-coupled to 7 single-element SNSPDs, and • a 30 µm core diameter multimode fiber butt-coupled to a 16 multi-element, SNSPD array. The measured insertion loss for each fiber device under emulated atmospheric conditions with D/r0 between 2 and 30 is presented. The multi-plane light conversion device shows a consistent ~1 dB loss more than the multimode fiber. Also presented is the measured uneven power splitting of the multiplane light conversion device, especially at lower D/r0. How this uneven power splitting contributes to system loss called blocking loss is discussed.

Fiber↗

NASA NTRSDate not supplied

Insertion Loss of a Multi-Plane Light Conversion Device with Few Mode Fiber Outputs Under Atmospheric Conditions

A key challenge of photon counting optical communication is delivering light with atmospherically distorted wavefronts from the telescope to detectors efficiently. When using fiber coupled single photon detectors, the efficiency of the transmittance is constrained by the modes supported by the fiber. The number of modes supported by a fiber depends on the size of the core. The larger the core, the more modes supported. However, commercial off the shelf superconducting nanowire single photon detectors (SNSPDs) are currently limited in area, which limits the core size of the fibers that can efficiently couple to the detectors. To increase the amount of light that can be delivered to the detectors, NASA Glenn Research Center is considering many different fiber/detector architectures. This paper compares insertion loss of the fiber device for two different architectures: • a multi-plane light conversion device to split the light from a 30 µm core diameter fiber into 7 separate, 15 µm core diameter few-mode fibers butt-coupled to 7 single-element SNSPDs, • and a 30 µm core diameter multimode fiber butt-coupled to a 16 multi-element, SNSPD array. The measured insertion loss for each fiber device under emulated atmospheric conditions with D/r0 between 2 and 30 is presented. The multi-plane light conversion device shows a consistent ~1 dB loss more than the multimode fiber. Also presented is the measured uneven power splitting of the multiplane light conversion device, especially at lower D/r0. How this uneven power splitting contributes to system loss called blocking loss is discussed.

Multi-plane light conversion device↗

NASA NTRS1978

Point source moving above a finite impedance reflecting plane - Experiment and theory

A widely used experimental version of the acoustic monopole consists of an acoustic driver of restricted opening forced by a discrete frequency oscillator. To investigate the effects of forward motion on this source, it was mounted above an automobile and driven over an asphalt surface at constant speed past a microphone array. The shapes of the received signal were compared to results computed from an analysis of a fluctuating-mass-type point source moving above a finite impedance reflecting plane. Good agreement was found between experiment and theory when a complex normal impedance representative of a fairly hard acoustic surface was used in the analysis.

Norum, T. D.↗

NASA NTRS1971

Analysis and design of antennas for air traffic collision avoidance systems.

The analysis and design procedure of an antenna for a CW Doppler radar system being developed for pilot warning of midair collision hazards is presented. The antenna consists of two vertical arrays of half-wavelength dipoles mounted near a circular conducting cylinder. Each vertical array is composed of three vertical dipoles. Each array provides relatively uniform illumination (2.3 dB) in the forward 180-deg angular segment of the horizontal plane and approximately plus or minus 10 to 15 deg coverage in the vertical plane. The antenna could be used in a two-mode operation, either in a standard monopulse radar system (sum and difference amplitude patterns) or in a system where amplitude and phase are the measurable quantities.

Balanis, C. A.↗

NASA NTRS1975

A statistical technique for processing radio interferometer data

The output of a radio interferometer is the Fourier transform of the object under investigation. Due to the limited coverage of the Fourier plane, the reconstruction of the image of the source is blurred by the beam of the synthesized array. A maximum-likelihood processing technique is described which uses the statistical properties of the received noise-like signals. This technique has been used extensively in the processing of large-aperture seismic arrays. This inversion method results in a synthesized beam that is more uniform, has lower sidelobes, and higher resolution than the normal Fourier transform methods. The maximum-likelihood method algorithm was applied successfully to very long baseline and short baseline interferometric data.

Papadopoulos, G. D.↗

NASA NTRS1984

Image-plane processing for improved computer vision

The proper combination of optical design with image plane processing, as in the mechanism of human vision, which allows to improve the performance of sensor array imaging systems for edge detection and location was examined. Two dimensional bandpass filtering during image formation, optimizes edge enhancement and minimizes data transmission. It permits control of the spatial imaging system response to tradeoff edge enhancement for sensitivity at low light levels. It is shown that most of the information, up to about 94%, is contained in the signal intensity transitions from which the location of edges is determined for raw primal sketches. Shading the lens transmittance to increase depth of field and using a hexagonal instead of square sensor array lattice to decrease sensitivity to edge orientation improves edge information about 10%.

Huck, F. O.↗

NASA NTRS1984

The Infrared Astronomical Satellite (IRAS) mission

The Infrared Astronomical Satellite (IRAS) consists of a spacecraft and a liquid helium cryostat that contains a cooled IR telescope. The telescope's focal plane assembly is cooled to less than 3 K, and contains 62 IR detectors in the survey array which are arranged so that every source crossing the field of view can be seen by at least two detectors in each of four wavelength bands. The satellite was launched into a 900 km-altitude near-polar orbit, and its cryogenic helium supply was exhausted on November 22, 1983. By mission's end, 72 percent of the sky had been observed with three or more hours-confirming scans, and 95 percent with two or more hours-confirming scans. About 2000 stars detected at 12 and 25 microns early in the mission, and identified in the SAO (1966) catalog, have a positional uncertainty ellipse whose axes are 45 x 9 arcsec for an hours-confirmed source.

Neugebauer, G.↗