Search NASA⌕ Search

SEARCH · Search NASA

Results for “ELECTROMAGNETIC RADIATION”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Global Aspects of Charged Particle Motion in Axially Symmetric Multipole Magnetic Fields

The motion of a single charged particle in the space outside of a compact region of steady currents is investigated. The charged particle is assumed to produce negligible electromagnetic radiation, so that its energy is conserved. The source of the magnetic field is represented as a point multipole. After a general description, attention is focused on magnetic fields with axial symmetry. Lagrangian dynamical theory is utilized to identify constants of the motion as well as the equations of motion themselves. The qualitative method of Stonner is used to examine charged particle motion in axisymmetric multipole fields of all orders. Although the equations of motion generally have no analytical solutions and must be integrated numerically to produce a specific orbit, a topological examination of dynamics is possible, and can be used, d la Stonner, to completely describe the global aspects of the motion of a single charged particle in a space with an axisymmetric multipole magnetic field.

Shebalin, John V.↗
NASA NTRS2011

Fiber-Optic Magnetic-Field-Strength Measurement System for Lightning Detection

A fiber-optic sensor system is designed to measure magnetic fields associated with a lightning stroke. Field vector magnitudes are detected and processed for multiple locations. Since physical limitations prevent the sensor elements from being located in close proximity to highly conductive materials such as aluminum, the copper wire sensor elements (3) are located inside a 4-cubic-in. (.66-cubic-cm) plastic housing sensor head and connected to a fiber-optic conversion module by shielded cabling, which is limited to the shortest length feasible. The signal path between the conversion module and the avionics unit which processes the signals are fiber optic, providing enhanced immunity from electromagnetic radiation incident in the vicinity of the measurements. The sensors are passive, lightweight, and much smaller than commercial B-dot sensors in the configuration which measures a three-dimensional magnetic field. The system is expandable, and provides a standard-format output signal for downstream processing. Inside of the sensor head, three small search coils, each having a few turns on a circular form, are mounted orthogonally inside the non-metallic housing. The fiber-optic conversion module comprises three interferometers, one for each search coil. Each interferometer has a high bandwidth optical phase modulator that impresses the signal received from its search coil onto its output. The output of each interferometer travels by fiber optic cable to the avionics unit, and the search coil signal is recovered by an optical phase demodulator. The output of each demodulator is fed to an analog-to-digital converter, whose sampling rate is determined by the maximum expected rate of rise and peak signal magnitude. The output of the digital processor is a faithful reproduction of the coil response to the incident magnetic field. This information is provided in a standard output format on a 50-ohm port that can be connected to any number of data collection and processing instruments and/or systems. The measurement of magnetic fields using fiber-optic signal processing is novel because it eliminates limitations of a traditional B-dot system. These limitations include the distance from the sensor to the measurement device, the potential for the signal to degrade or be corrupted by EMI from lightning, and the size and weight of the sensor and associated plate.

Gurecki, Jay↗
NASA NTRS2011

The Integrated Science Investigation of the Sun (ISIS): Energetic Particle Measurements for the Solar Probe Plus Mission

One of the major goals of NASA's Solar Probe Plus (SPP) mission is to determine the mechanisms that accelerate and transport high-energy particles from the solar atmosphere out into the heliosphere. Processes such as coronal mass ejections and solar flares, which peak roughly every 11 years around solar maximum, release huge quantities of energized matter, magnetic fields and electromagnetic radiation into space. The high-energy particles, known as solar energetic particles or SEPs, present a serious radiation threat to human explorers living and working outside low-Earth orbit and to technological assets such as communications and scientific satellites in space. This talk describes the Integrated Science Investigation of the Sun (ISIS) - Energetic Particle Instrument suite. ISIS measures key properties such as intensities, energy spectra, composition, and angular distributions of the low-energy suprathermal source populations, as well as the more hazardous, higher energy particles ejected from the Sun. By making the first-ever direct measurements of the near-Sun regions where the acceleration takes place, ISIS will provide the critical measurements that, when integrated with other SPP instruments and with solar and interplanetary observations, will lead to a revolutionary new understanding of the Sun and major drivers of solar system space weather.

McComas, D. J.↗
NASA NTRS2006

Semiconductor Bolometers Give Background-Limited Performance

Semiconductor bolometers that are capable of detecting electromagnetic radiation over most or all of the infrared spectrum and that give background-limited performance at operating temperatures from 20 to 300 K have been invented. The term background-limited performance as applied to a bolometer, thermopile, or other infrared detector signifies that the ability to detect infrared signals that originate outside the detector is limited primarily by thermal noise attributable to the background radiation generated external to the bolometer. The signal-to-noise ratios and detectivities of the bolometers and thermopiles available prior to this invention have been lower than those needed for background-limited performance by factors of about 100 and 10, respectively. Like other electrically resistive bolometers, a device according to the invention exhibits an increase in electrical resistance when heated by infrared radiation. Depending on whether the device is operated under the customary constant- current or constant-voltage bias, the increase in electrical resistance can be measured in terms of an increase in voltage across the device or a decrease in current through the device, respectively. In the case of a semiconductor bolometer, it is necessary to filter out visible and shorter-wavelength light that could induce photoconductivity and thereby counteract all or part of the desired infrared- induced increase in resistance. The basic semiconductor material of a bolometer according to the invention is preferably silicon doped with one or more of a number of elements, each of which confers a different variable temperature coefficient of resistance. Suitable dopants include In, Ga, S, Se, Te, B, Al, As, P, and Sb. The concentration of dopant preferably lies in the range between 0.1 and 1,000 parts per billion.

Goebel, John↗
NASA NTRS2003

120-GHz HEMT Oscillator With Surface-Wave-Assisted Antenna

Two monolithic microwave integrated circuits (MMICs) have been designed and built to function together as a source of electromagnetic radiation at a frequency of 120 GHz. One of the MMICs is an oscillator and is the highest-power 120-GHz oscillator reported thus far in the literature. The other MMIC is an end-fire antenna that radiates the oscillator signal. Although these MMICs were constructed as separate units and electrically connected with wire bonds, future oscillator/ antenna combinations could readily be fabricated as monolithic integrated units. Such units could be used as relatively high-power solid-state microwave sources in diverse applications that include automotive radar, imaging, scientific instrumentation, communications, and radio astronomy. As such, these units would be attractive alternatives to vacuum-tube oscillators, which are still used to obtain acceptably high power in the frequency range of interest. The oscillator (see figure) includes a high-electron-mobility transistor (HEMT), with gate-periphery dimensions of 4 by 37 m, in a common-source configuration. The series feedback element of the oscillator is a grounded coplanar waveguide (CPW) at the source. The HEMT is biased for class-A operation (meaning that current is conducted throughout the oscillation cycle) to maximize the output power of the oscillator. Input and output impedance-matching circuit elements are designed to maximize output power and to establish the conditions needed for oscillation. The design of the antenna takes advantage of surface waves, which, heretofore, have been regarded as highly disadvantageous because they can leak power and degrade the performances of antennas that have not been designed to exploit them. Measures taken to suppress surface waves have included complex machining of circuit substrates and addition of separate substrates. These measures are difficult to implement in standard MMIC fabrication processes. In contrast, because the design of the present antenna eliminates the need to suppress surface waves, the fabrication of the antenna is fully compatible with standard MMIC fabrication processes.

Samoska, Lorene↗
NASA NTRS2012

Materials, Structures and Manufacturing: An Integrated Approach to Develop Expandable Structures

Membrane dominated space structures are lightweight and package efficiently for launch; however, they must be expanded (deployed) in-orbit to achieve the desired geometry. These expandable structural systems include solar sails, solar power arrays, antennas, and numerous other large aperture devices that are used to collect, reflect and/or transmit electromagnetic radiation. In this work, an integrated approach to development of thin-film damage tolerant membranes is explored using advanced manufacturing. Bio-inspired hierarchical structures were printed on films using additive manufacturing to achieve improved tear resistance and to facilitate membrane deployment. High precision, robust expandable structures can be realized using materials that are both space durable and processable using additive manufacturing. Test results show this initial work produced higher tear resistance than neat film of equivalent mass. Future research and development opportunities for expandable structural systems designed using an integrated approach to structural design, manufacturing, and materials selection are discussed.

Belvin, W. Keith↗
NASA NTRS2012

Concept-Development of a Structure Supported Membrane for Deployable Space Applications - From Nature to Manufacture and Testing

Current space applications of membrane structures include large area solar power arrays, solar sails, antennas, and numerous other large aperture devices like the solar shades of the new James Webb Space Telescope. These expandable structural systems, deployed in-orbit to achieve the desired geometry, are used to collect, reflect and/or transmit electromagnetic radiation. This work, a feasibility study supporting a diploma thesis, describes the systematic process for developing a biologically inspired concept for a structure supported (integrated) membrane, that features a rip stop principle, makes self-deployment possible and is part of an ultra-light weight space application. Novel manufacturing of membrane prototypes and test results are presented for the rip-stop concepts. Test data showed that the new membrane concept has a higher tear resistance than neat film of equivalent mass.

Zander, Martin↗
NASA NTRS2012

Fabrication of Compact Superconducting Lowpass Filters for Ultrasensitive Detectors

It is extremely important for current and future far-infrared and sub-millimeter ultrasensitive detectors, which include transition edge sensors (TES) and microwave kinetic inductance detectors, to be adequately filtered from stray electromagnetic radiation in order to achieve their optimal performance. One means of filtering stray radiation is to block leakage associated with electrical connections in the detector environment. Here we discuss a fabrication methodology for realizing non-dissipative planar filters imbedded in the wall of the detector enclosure to limit wave propagation modes up to far-infrared frequencies. Our methodology consists of fabricating a boxed stripline transmission line, in which a superconducting (Nb, Mo, or Al) transmission line is encased in a silicon dioxide dielectric insulator coated with a metallic shell. We report on achieved attenuation and return loss and find that it replicates the simulated data to a high degree.

Brown, Ari↗
NASA NTRS2014

A New Standard Pulsar Magnetosphere

In view of recent efforts to probe the physical conditions in the pulsar current sheet, we revisit the standard solution that describes the main elements of the ideal force-free pulsar magnetosphere. The simple physical requirement that the electric current contained in the current layer consists of the local electric charge moving outward at close to the speed of light yields a new solution for the pulsar magnetosphere everywhere that is ideal force-free except in the current layer. The main elements of the new solution are as follows: (1) the pulsar spindown rate of the aligned rotator is 23% larger than that of the orthogonal vacuum rotator; (2) only 60% of the magnetic flux that crosses the light cylinder opens up to infinity; (3) the electric current closes along the other 40%, which gradually converges to the equator; (4) this transfers 40% of the total pulsar spindown energy flux in the equatorial current sheet, which is then dissipated in the acceleration of particles and in high-energy electromagnetic radiation; and (5) there is no separatrix current layer. Our solution is a minimum free-parameter solution in that the equatorial current layer is electrostatically supported against collapse and thus does not require a thermal particle population. In this respect, it is one more step toward the development of a new standard solution. We discuss the implications for intermittent pulsars and long-duration gamma-ray bursts. We conclude that the physical conditions in the equatorial current layer determine the global structure of the pulsar magnetosphere.

pulsars: general↗
NASA NTRS2013

Distributive, Non-destructive Real-time System and Method for Snowpack Monitoring

A ground-based system that provides quasi real-time measurement and collection of snow-water equivalent (SWE) data in remote settings is provided. The disclosed invention is significantly less expensive and easier to deploy than current methods and less susceptible to terrain and snow bridging effects. Embodiments of the invention include remote data recovery solutions. Compared to current infrastructure using existing SWE technology, the disclosed invention allows more SWE sites to be installed for similar cost and effort, in a greater variety of terrain; thus, enabling data collection at improved spatial resolutions. The invention integrates a novel computational architecture with new sensor technologies. The invention's computational architecture is based on wireless sensor networks, comprised of programmable, low-cost, low-powered nodes capable of sophisticated sensor control and remote data communication. The invention also includes measuring attenuation of electromagnetic radiation, an approach that is immune to snow bridging and significantly reduces sensor footprints.

Frolik, Jeff↗
NASA NTRS2013

Superconducting Metallic Glass Transition-Edge-Sensors

A superconducting metallic glass transition-edge sensor (MGTES) and a method for fabricating the MGTES are provided. A single-layer superconducting amorphous metal alloy is deposited on a substrate. The single-layer superconducting amorphous metal alloy is an absorber for the MGTES and is electrically connected to a circuit configured for readout and biasing to sense electromagnetic radiation.

Hays, Charles C.↗
NASA NTRS2014

Atomic Layer Deposition of Chemical Passivation Layers and High Performance Anti-Reflection Coatings on Back-Illuminated Detectors

A back-illuminated silicon photodetector has a layer of Al2O3 deposited on a silicon oxide surface that receives electromagnetic radiation to be detected. The Al2O3 layer has an antireflection coating deposited thereon. The Al2O3 layer provides a chemically resistant separation layer between the silicon oxide surface and the antireflection coating. The Al2O3 layer is thin enough that it is optically innocuous. Under deep ultraviolet radiation, the silicon oxide layer and the antireflection coating do not interact chemically. In one embodiment, the silicon photodetector has a delta-doped layer near (within a few nanometers of) the silicon oxide surface. The Al2O3 layer is expected to provide similar protection for doped layers fabricated using other methods, such as MBE, ion implantation and CVD deposition.

Hoenk, Michael E.↗
NASA NTRS2014

Methods to Fabricate and Improve Stand-alone and Integrated Filters

Embodiments of the invention provide for fabricating a filter, for electromagnetic radiation, in at least three ways, including (1) fabricating integrated thin film filters directly on a detector; (2) fabricating a free standing thin film filter that may be used with a detector; and (3) treating an existing filter to improve the filter's properties.

Greer, Frank↗
NASA NTRS2015

Sparsely-Bonded CMOS Hybrid Imager

A method and device for imaging or detecting electromagnetic radiation is provided. A device structure includes a first chip interconnected with a second chip. The first chip includes a detector array, wherein the detector array comprises a plurality of light sensors and one or more transistors. The second chip includes a Read Out Integrated Circuit (ROIC) that reads out, via the transistors, a signal produced by the light sensors. A number of interconnects between the ROIC and the detector array can be less than one per light sensor or pixel.

Cunningham, Thomas J.↗
NASA NTRS2013

Absorption and Scattering by Molecules and Particles

The Earth's atmosphere absorbs, scatters, and emits electromagnetic radiation. Although air molecules are the primary actors in these processes, aerosol particles are also present ubiquitously and modify the radiation field. In fact, this modification constitutes the very physical basis of aerosol remote sensing. Whenever clouds are present, they have a much larger influence on radiation which largely overshadows the aerosol impact. Therefore, in aerosol remote sensing, one often has to limit observations to cloudless conditions and screen cloudy pixels. In the solar part of the spectrum, molecular absorption is mostly limited to ultraviolet (UV; ozone) and near-infrared (near-IR; carbon dioxide, water vapor) wavelengths and is characterized by strong and narrow oxygen bands. A brief description of atmospheric molecular absorption is presented in Section 2.2. Shortwave aerosol remote sensing is usually performed outside the absorption bands, but some instruments also have channels capturing absorption bands with the objective of quantifying gaseous components.

remote sensing↗
NASA NTRS2015

Wide-Field InfraRed Survey Telescope (WFIRST) Mission and Synergies with LISA and LIGO-Virgo

The Wide-Field InfraRed Survey Telescope (WFIRST) is a NASA space mission in study for launch in 2024. It has a 2.4 m telescope, wide-field IR instrument operating in the 0.7 - 2.0 micron range and an exoplanet imaging coronagraph instrument operating in the 400 - 1000 nm range. The observatory will perform galaxy surveys over thousands of square degrees to J=27 AB for dark energy weak lensing and baryon acoustic oscillation measurements and will monitor a few square degrees for dark energy SN Ia studies. It will perform microlensing observations of the galactic bulge for an exoplanet census and direct imaging observations of nearby exoplanets with a pathfinder coronagraph. The mission will have a robust and wellfunded guest observer program for 25% of the observing time. WFIRST will be a powerful tool for time domain astronomy and for coordinated observations with gravitational wave experiments. Gravitational wave events produced by mergers of nearby binary neutron stars (LIGO-Virgo) or extragalactic supermassive black hole binaries (LISA) will produce electromagnetic radiation that WFIRST can observe.

Wide-Field InfraRed Survey Telescope (WFIRST) Miss↗
NASA NTRS2015

Active Collision Avoidance for Planetary Landers

The use of automotive radar systems are being evaluated for collision avoidance in planetary landers. Our focus is to develop a low-cost, light-weight collision avoidance system that overcomes the drawbacks identified with optical-based systems. We also seek to complement the Autonomous Landing and Hazard Avoidance Technology system by providing mission planners an alternative system that can be used on low-cost, small robotic missions and in close approach. Our approach takes advantage of how electromagnetic radiation interacts with solids. As the wavelength increases, the sensitivity of the radiation to isolated solids of a specific particle size decreases. Thus, rocket exhaust-blown dust particles, which have major significance in visible wavelengths, have much less significance at radar wavelengths.

Rickman, Doug↗
NASA NTRS2016

Beam Wave Considerations for Optical Link Budget Calculations

The bounded beam wave nature of electromagnetic radiation emanating from a finite size aperture is considered for diffraction-based link power budget calculations for an optical communications system. Unlike at radio frequency wavelengths, diffraction effects are very important at optical wavelengths. In the general case, the situation cannot be modeled by supposing isotropic radiating antennas and employing the concept of effective isotropic radiated power. It is shown here, however, that these considerations are no more difficult to treat than spherical-wave isotopic based calculations. From first principles, a general expression governing the power transfer for a collimated beam wave is derived and from this are defined the three regions of near-field, first Fresnel zone, and far-field behavior. Corresponding equations for the power transfer are given for each region. It is shown that although the well-known linear expressions for power transfer in the far-field hold for all distances between source and receiver in the radio frequency case, nonlinear behavior within the first Fresnel zone must be accounted for in the optical case at 1550 nm with typical aperture sizes at source/receiver separations less that 100 km.

Wave Propagation↗