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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Sensors and detectors in NASA's future missions

Advances in electronics are responsible for major improvements in NASA's sensing and detection capabilities for future space missions. Technologies such as charge-transfer devices, tunable diode lasers, millimeter and submillimeter wave solid-state receiver components, large-scale circuit integration, new electronic materials and processing techniques, and novel detector electronics are contributing to the goal of a tenfold increase in the capacity of data collection from future platforms and will be used for space exploration and utilization.

Rubin, B.↗
NASA NTRS1994

Gamma-ray and millimeter-wave emissions from the 1991 June X-class solar flares

We have studied the spectacular 1991 June X-class flares using gamma-ray data from the Charged Particle Detectors (CPDs) of the Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (CGRO) and 80 GHz millimeter data from Nobeyama, Japan. The CPDs were the only CGRO instrument that did not saturate during the extremely intense 1991 June 4 flare. We have shown that for this flare the CPDs respond to MeV photons, most of which are due to bremsstrahlung produced by relativistic electrons at the Sun. We have further shown that the gamma-ray and millimeter observations agree numerically if the 80 GHz radiation is gyrosynchrotron radiation produced by trapped electrons and the gamma rays are thick-target bremsstrahlung due to electrons precipitating out of the trap. The requirement that the trapping time obtained from the numerical comparison be consistent with the observed time profiles implies a magnetic field between about 200 and 300 G and an electron spectral index between about 3 to 5. By comparing the CPD observations with both the 80 GHz data and nuclear line data from the Energetic Gamma Ray Experiment Telescope (EGRET) and the Oriented Scintillation Spectroscopy Experiment (OSSE) on CGRO for the flares of June 4, 6, 9, and 11, we found that the ratio of the CPD counts to both the millimeter flux densities and the nuclear line fluences decreases with decreasing flare heliocentric angle. All of these flares were produced in the same active region. We interpreted this result in terms of a loop model in which the gyrosynchrotron emission is produced in the coronal portion of the loop where the electrons are kept isotropic by pitch angle scattering due to plasma turbulence, while the bremsstrahlung is produced by precipitating electrons that interact anisotropically. We found that the trapping time in the coronal portion is time dependent, reaching a minimum of about 10 s at the peak of the CPD count rate. We suggested the damping of the turbulence as a possible reason for the variation of the trapping time. turbulence as a possible reason for the variation of the trapping time.

Ramaty, Reuven↗
NASA NTRS1987

Technology for satellite power conversion

The work is this reporting period was concentrated on electronically calibrating the bolometer detectors. The calibration is necessary for two reasons: first, the power delivered to the rectifying circuit must be known in order to choose a diode with the appropriate barrier height, and second, the power captured by the antenna must be measured if the efficiency of the rectenna is to be divided into antenna efficiency and rectification efficiency. The millimeter wave region operation of the bolometers was simulated with a VHF (10 to 90 MHz) test signal. These detectors are accurate to within roughly 10%. The typical responsivity of the bolometers is 10 volts/watt and the NEP at 20 Hz is 5 times 10 to the minus 9th power W(Hz)-1/2.

Gouker, M. A.↗
NASA NTRS1990

Imaging Antenna Structure For Submillimeter Wavelengths

Integrated-circuit antenna structure contains two-dimensional array of antennas and antenna reflectors. In receiving mode, each antenna acts as part of detector for one picture element in millimeter- or submillimeter-wavelength imaging radar system. Millimeter-wave imaging system used to view objects through fog, smoke, or smog with resolution intermediate between microwave and visible-light imaging systems. Antenna elements, supports, and reflectors made by integrated-circuit techniques. Structures fabricated on front and back substrates separately. Substrates then joined. Inexpensive way to provide large number of small antenna elements required for imaging, all mounted rigidly in way that does not degrade operation.

Rebeiz, G.↗
NASA NTRS1991

A wide-band monolithic quasi-optical power meter for millimeter- and submillimeter-wave applications

A novel monolithic power meter has been developed for submillimeter-wave applications (100 GHz to 10 THz). The detector is a large-area bismuth bolometer integrated on a 1.2-micron-thick dielectric membrane. This approach results in a wide-band, high-responsivity detector. The power meter is simple to fabricate, is inexpensive, and can be easily calibrated using a low-frequency network. Quasi-optical measurements at 90, 140, and 240 GHz show that the bolometer is polarization-independent and could be modeled by a simple transmission line model. Absolute power measurements at 90, 140, and 240 GHz show a + or - 5 percent accuracy and agree well with a calibrated Anritsu power meter at 90 GHz. Potential application areas are power calibration, antenna coupling efficiency measurements, and absolute power measurements from solid-state devices and far-infrared lasers at submillimeter wavelengths. Absolute output power measurements on a 220-280 GHz tripler using the quasi-optical power meter are presented as an application example.

Ling, Curtis C.↗
NASA NTRS1998

Multi-Bandwidth Frequency Selective Surfaces for Near Infrared Filtering: Design and Optimization

Frequency selective surfaces are widely used in the microwave and millimeter wave regions of the spectrum for filtering signals. They are used in telecommunication systems for multi-frequency operation or in instrument detectors for spectroscopy. The frequency selective surface operation depends on a periodic array of elements resonating at prescribed wavelengths producing a filter response. The size of the elements is on the order of half the electrical wavelength, and the array period is typically less than a wavelength for efficient operation. When operating in the optical region, diffraction gratings are used for filtering. In this regime the period of the grating may be several wavelengths producing multiple orders of light in reflection or transmission. In regions between these bands (specifically in the infrared band) frequency selective filters consisting of patterned metal layers fabricated using electron beam lithography are beginning to be developed. The operation is completely analogous to surfaces made in the microwave and millimeter wave region except for the choice of materials used and the fabrication process. In addition, the lithography process allows an arbitrary distribution of patterns corresponding to resonances at various wavelengths to be produced. The design of sub-millimeter filters follows the design methods used in the microwave region. Exacting modal matching, integral equation or finite element methods can be used for design. A major difference though is the introduction of material parameters and thicknesses that may not be important in longer wavelength designs. This paper describes the design of multi- bandwidth filters operating in the 1-5 micrometer wavelength range. This work follows on a previous design. In this paper extensions based on further optimization and an examination of the specific shape of the element in the periodic cell will be reported. Results from the design, manufacture and test of linear wedge filters built using microlithographic techniques and used in spectral imaging applications will be presented.

Cwik, Tom↗
NASA NTRS1999

Multi-Bandwidth Frequency Selective Surfaces for Near Infrared Filtering: Design and Optimization

Frequency selective surfaces are widely used in the microwave and millimeter wave regions of the spectrum for filtering signals. They are used in telecommunication systems for multi-frequency operation or in instrument detectors for spectroscopy. The frequency selective surface operation depends on a periodic array of elements resonating at prescribed wavelengths producing a filter response. The size of the elements is on the order of half the electrical wavelength, and the array period is typically less than a wavelength for efficient operation. When operating in the optical region, diffraction gratings are used for filtering. In this regime the period of the grating may be several wavelengths producing multiple orders of light in reflection or transmission. In regions between these bands (specifically in the infrared band) frequency selective filters consisting of patterned metal layers fabricated using electron beam lithography are beginning to be developed. The operation is completely analogous to surfaces made in the microwave and millimeter wave region except for the choice of materials used and the fabrication process. In addition, the lithography process allows an arbitrary distribution of patterns corresponding to resonances at various wavelengths to be produced. The design of sub-millimeter filters follows the design methods used in the microwave region. Exacting modal matching, integral equation or finite element methods can be used for design. A major difference though is the introduction of material parameters and thicknesses tha_ may not be important in longer wavelength designs. This paper describes the design of multi-bandwidth filters operating in the I-5 micrometer wavelength range. This work follows on previous design [1,2]. In this paper extensions based on further optimization and an examination of the specific shape of the element in the periodic cell will be reported. Results from the design, manufacture and test of linear wedge filters built using micro-lithographic techniques and used ir spectral imaging applications will be presented.

Cwik, Tom↗
NASA NTRS2006

Polarimeter Arrays for Cosmic Microwave Background Measurements

We discuss general system architectures and specific work towards precision measurements of Cosmic Microwave Background (CMB) polarization. The CMB and its polarization carry fundamental information on the origin, structure, and evolution of the universe. Detecting the imprint of primordial gravitational radiation on the faint polarization of the CMB will be difficult. The two primary challenges will be achieving both the required sensitivity and precise control over systematic errors. At anisotropy levels possibly as small as a few nanokelvin, the gravity-wave signal is faint compared to the fundamental sensitivity limit imposed by photon arrival statistics, and one must make simultaneous measurements with large numbers, hundreds to thousands, of independent background-limited direct detectors. Highly integrated focal plane architectures, and multiplexing of detector outputs, will be essential. Because the detectors, optics, and even the CMB itself are brighter than the faint gravity-wave signal by six to nine orders of magnitude, even a tiny leakage of polarized light reflected or diffracted from warm objects could overwhelm the primordial signal. Advanced methods of modulating only the polarized component of the incident radiation will play an essential role in measurements of CMB polarization. One promising general polarimeter concept that is under investigation by a number of institutions is to first use planar antennas to separate millimeter-wave radiation collected by a lens or horn into two polarization channels. Then the signals can be fed to a pair of direct detectors through a planar circuit consisting of superconducting niobium microstrip transmission lines, hybrid couplers, band-pass filters, and phase modulators to measure the Stokes parameters of the incoming radiation.

Stevenson, Thomas↗
NASA NTRS1993

The advanced cosmic microwave explorer - A millimeter-wave telescope and stabilized platform

We have developed and flown a 1 m diameter Gregorian telescope system for measurements of anisotropy in the Cosmic Background Radiation (CBR). The telescope is incorporated in a balloon-borne stabilized platform with arcminute stabilization capability. To date, the system has flown four times and observed from the ground at the South Pole twice. The telescope has used both coherent and incoherent detectors. We describe the development of the telescope, pointing platform, and one of the receivers employed in making measurements of the CBR. Performance of the system during the first flight and operation on the ground at the South Pole are described, and the quality of the South Pole as a millimeter wave observing site is discussed.

Meinhold, P. R.↗
NASA NTRS2011

The Impact of Standard Semiconductor Fabrication Processes on Polycrystalline Nb Thin Film Surfaces

Polycrystalline superconducting Nb thin films are extensively used for submillimeter and millimeter transmission line applications and, less commonly, used in microwave kinetic inductance detector (MKID) applications. The microwave and mm-wave loss in these films is impacted, in part, by the presence of surface nitrides and oxides. In this study, glancing incidence x-ray diffraction was used to identify the presence of niobium nitride and niobium monoxide surface layers on Nb thin films which had been exposed to chemicals used in standard photolithographic processing. A method of mitigating the presence of ordered niobium monoxide surface layers is presented. Furthermore, we discuss the possibility of using glancing incidence x-ray diffraction as a non-destructive diagnostic tool for evaluating the quality of Nb thin films used in MKIDs and transmission lines. For a given fabrication process, we have both the x-ray diffraction data of the surface chemistry and a measure of the mm-wave and microwave loss, the latter being made in superconducting resonators.

superconducting films↗
NASA NTRS2002

Submillimeter Laboratory Investigations: Spectroscopy and Collisions

Currently, millimeter-wave and submillimeter-wave spectroscopy is conducted in our laboratory on several different types of spectrometers. Our standard spectrometer utilizes the output of a phase-locked klystron operating in the 40-60 GHz region, which is sent into a crossed-waveguide harmonic generator, or "multiplier". The high frequency millimeter-and submillimeter-wave radiation is transmitted via quasi-optical techniques through an absorption cell and then onto a detector, which is either an InSb hot electron bolometer cooled to 1.4 K or a Si bolometer cooled to 0.3 K. The detector response is sent to a computer for measurement and analysis. The frequency range produced and detected in this manner goes from 80 GHz to upwards of 1 THz. Spectra are normally taken with source modulation, with line frequencies typically measured to an accuracy of 50-100 kHz. Higher accuracy is available when needed. Recently, we developed a new, broad-band spectrometer in our laboratory based on a free-running backward wave oscillator (BWO) of Russian manufacture as the primary source of radiation. The so-called FASSST (fast-scan submillimeter spectroscopic technique) system uses fast-scan and optical calibration methods rather than the traditional locking techniques. The output power from the BWO is split such that 90% goes into the absorption cell while 10% is coupled to a 40-meter Fabry-Perot cavity, which yields fringe? for frequency measurement. Results from this spectrometer on the spectrum of nitric acid (HNO3) show that 100 GHz of spectral data can be obtained in 5 seconds with a measurement accuracy of 50 kHz. Currently, the frequency range of the FASSST system in our laboratory is roughly 100-700 GHz.

Herbst, Eric↗
NASA NTRS1983

Tracking antenna arrays for near-millimeter waves

A two-dimensional monolithic array has been developed that gives the elevation and azimuth of point source targets. The array is an arrangement of rows and columns of antennas and bismuth bolometer detectors on a fused quartz substrate. Energy is focused onto the array through a lens placed on the back side of the substrate. At 1.38 mm with a 50 mm diameter objective lens, the array has demonstrated a positioning accuracy of 26 arcmin. In a differential mode this precision improves to 9 arcsec, limited by the mechanics of the rotating stage. This tracking could be automated to a fast two-step procedure where a source is first located to the nearest row and column, and then precisely located by scanning. With signal processing the array should be able to track multiple sources.

Tong, P. P.↗
NASA NTRS1986

Near millimeter wave imaging/multi-beam integrated antennas

Some preliminary results on a mixer design which is suitable for integration with tapered slot antennas have been obtained and published. This mixer design was tested both in a 4 to 10 GHz model, and (slightly modified) at 94 GHz. The latter utilized the same Hewlett-Packard beam-lead diodes which were used as detector diodes in the linearly tapered slot antennas (LTSA) arrays. These diodes are the most rugged to be found, and generally survive well on the flexible Kapton substrates. The 4 to 10 GHz version of this mixer has less than 6 dB conversion loss over an octave bandwidth. It uses a slot ring in a balanced configuration, and requires the LO to be fed through a separate port. A different design for a mixer which may be integrated with an LTSA antenna element is discussed. This mixer was tested at 38 GHz with the same HP beam-lead diodes, and has less than 10 dB conversion loss. Further work on mixers has emphasized theoretical modeling, using a computer program, which takes into account the effect of excess noise of Schottky-barrier diodes for the first time. Calculated results agree quantitatively with measured results on millimeter wave mixers.

Yngvesson, K. Sigfrid↗
NASA NTRS1992

Millimeter-wave double-dipole antennas for high-gain integrated reflector illumination

A double-dipole antenna backed by a ground plane has been fabricated for submillimeter wavelengths. The double-dipole antenna is integrated on a thin dielectric membrane with a planar detector at its center. Measured feed patterns at 246 GHz agree well with theory and demonstrate a rotationally symmetric pattern with high coupling efficiency to Gaussian beams. The input impedance is around 50 ohms, and will match well to a Schottky diode or SIS detector. The double-dipole antenna served as the feed for a small machined parabolic reflector. The integrated reflector had a measured gain of 37 dB at 119 microns. This makes the double-dipole antenna ideally suited as a feed for high resolution tracking or for long focal length Cassegrain antenna systems.

Filipovic, Daniel F.↗
NASA NTRS1985

Model Experiments with Slot Antenna Arrays for Imaging

A prototype imaging system at 31 GHz was developed, which employs a two-dimensional (5x5) array of tapered slot antennas, and integrated detector or mixer elements, in the focal plane of a prime-focus paraboloid reflector, with an f/D=1. The system can be scaled to shorter millimeter waves and submillimeter waves. The array spacing corresponds to a beam spacing of approximately one Rayleigh distance and a two-point resolution experiment showed that two point-sources at the Rayleigh distance are well resolved.

Johansson, J. F.↗