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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Motion requirements for antennas in geostationary earth orbit

Design dependencies of antennas in geostationary earth orbits are evaluated, and the tradeoffs between the optical geoscientific goals and achievable architecture capabilities are surveyed. The radial and tangential resolutions are investigated to ascertain whether mission objectives of the antennas may be satisfied. The effects of off-nadir scanning are examined to determine the limits of scan based on realizable resolution. Formulas for raster and spiral scanning time are reviewed and examined to find necessary accelerations. The resulting knowledge is used to evaluate two possible layouts. Torques necessary for slewing these configurations are calculated. A number of rotatory actuators are reviewed to evaluate future design goals for on-board momentum compensation.

Tentor, Lawrence B.↗
NASA NTRS1970

A proposed laser measurement system for determining surface contour

Electro-optical system can scan a large /100 ft./ antenna in 30 seconds. Comparison of the reflected signal with a reference signal from a Pockel-cell modulator driver yields a signal that can be correlated with the distance covered by the laser. A scanning arrangement then enables contour measurement.

Neubert, H. D.↗
NASA NTRS1986

Microwave backscatter coefficients of artificially grown first-year sea ice

The radar backscattering coefficient of simulated first year sea ice was measured at 5.2, 9.6, 13.6, and 16.6 GHz, using a dual-antenna FM-CW scatterometer. The measurements were corrected for antenna separation and beamwidth, to obtain true values of scattering coefficient. Above 15 deg, snow-covered and rough gray ice have similar angular responses, while the decrease in scattering coefficient with incidence angle is more rapid for smoother surfaces. True scattering coefficients and surface roughness data estimated with an antenna-beamwidth correction based on a physical-optics model give values close to those measured.

Xue, D.↗
NASA NTRS1988

Plan of propagation and communication experiments using ETS-VI

In 1992, an Engineering Test Satellite VI is scheduled to be launched by an H-II rocket. The missions of ETS-VI are to establish basic technologies of inter-satellite communications using millimeter waves and optical beams and fix satellite communications using multibeam antenna on board the satellite. Several kinds of frequency bands will be used for the communications missions. However, these frequencies can be used for propagation experiments.

Ohmori, Shingo↗
NASA NTRS1989

Enhanced imaging of reflector antenna surface distortion using microwave holography

Two signal processing techniques are discussed that improve the accuracy of a microwave holographic measurement by removing unwanted signals from the aperture distribution: pattern simulation and subtraction, and time domain filtering. Pattern simulation and subtraction involves modeling unwanted scattering mechanisms and then removing them from the measured far-field data. Measurements taken on a focal point geometry and a Cassegrain geometry at 11 GHz were processed by the holographic analysis system. Pattern simulation and subtraction was applied to both geometries. Surface deformation profiles generated for the Cassegrain antenna by this system were compared to an optical measurement of the main reflector surface.

Gilmore, Sean W.↗
NASA NTRS1991

Amplitude and phase-shaping effects in beamwaveguides

Results are presented of an investigation on improvements in a geometrical optics (GO) design of a beam-waveguide antenna for operation at multiple frequency bands. Improvements might be possible by changing the design of the lower-frequency input pattern to the beam waveguide. The effects of amplitude and phase shaping the input pattern have been studied with an aperture diffraction model. Accurate vector near-field computations were made rapidly with a spherical wave expansion of the input and scattered fields. Numerical results indicate that for aperture sizes of less than 30 wavelengths, there is insufficient control on defocusing due to amplitude and phase shaping. Design tradeoffs on spillover loss and defocusing are possible by changing the amplitude and phase distribution of the input wavefront for larger size apertures.

Rengarajan, Sembiam R.↗
NASA NTRS2001

Low Noise 1.2 THz SIS Receiver

We present the development of a low noise superconductor insulator superconductor (SIS) mixer for the 1.1 - 1.25 THz heterodyne receiver of FIRST space radiotelescope. The quasi-optical SIS mixer has two NbTiN/AlN/Nb junctions with critical current density 30 kA/sq cm. The individual junction area is close to 0.65 square micrometers. The SIS junctions are coupled to the optical input beam through a planar double slot antenna and a Si hyperhemispherical lens. The minimum DSB receiver noise temperature is 650 K, about 12 hv/k.

Karpov, A.↗
NASA NTRS2004

Near Earth Architectural Options for a Future Deep Space Optical Communications Network

In the near future the National Aeronautics and Space Administration anticipates a significant increase in demand for long-haul communications services from deep space to Earth. Distances will range from 0.1 to 40 AU, with data rate requirements in the 1's to 1000's of Mbits/second. The near term demand is driven by NASA's Space Science Enterprise which wishes to deploy more capable instruments onboard spacecraft and increase the number of deep space missions. The long term demand is driven by missions with extreme communications challenges such as very high data rates from the outer planets, supporting sub-surface exploration, or supporting NASA's Human Exploration and Development of Space Enterprise beyond Earth orbit. Laser communications is a revolutionary communications technology that will dramatically increase NASA's ability to transmit information across the solar system. Lasercom sends information using beams of light and optical elements, such as telescopes and optical amplifiers, rather than RF signals, amplifiers, and antennas. This paper provides an overview of different network options at Earth to meet NASA's deep space lasercom requirements. It is based mainly on work done for the Mars Laser Communications Demonstration Project, a joint project between NASA's Goddard Space Flight Center (GSFC), the Jet Propulsion Laboratory, California Institute of Technology (JPL), and the Massachusetts Institute of Technology Lincoln Laboratory (MIT/LL). It reports preliminary conclusions from the Mars Lasercom Study conducted at MIT/LL and on additional work done for the Tracking and Data Relay Satellite System Continuation Study at GSFC. A lasercom flight terminal will be flown on the Mars Telesat Orbiter (MTO) to be launched by NASA in 2009, and will be the first high rate deep space demonstration of this revolutionary technology.

Edwards, B. L.↗
NASA NTRS2003

Packaging Considerations for Integrated RF Microphotonic Receiver at Ka-Band

The NASA Computing, Information and Communications Technology (CICT) Program is supporting the development of an RF microphotonic Ka-band receiver. The receiver consists of a lithium niobate micro-disk that enables the incoming RF signal (up to Ka-band) to be coupled to the optical signal (approx. 200 THz). The modulated optical signal is detected by the high-speed photonic signal processing electronics. When compared with an all-electronic approach, the microphotonic receiver technology offers 1 Ox smaller volume, smaller weight, and smaller power consumption, greater sensitivity, and optical isolation for applications in extreme environments. It could potentially be implemented to support planetary surface-to-surface and surface-to-relay communications, as well as high-data-rate inter-satellite links. We are currently studying a number of fabrication and integration issues that could result as this technology is advanced for potential insertion into a NASA mission. The results of our preliminary effort to integrate the RF microphotonic receiver components (e.g., the lithium niobate micro-disk, the optical elements, and the Ka-band patch antenna) on an etched silicon wafer will be presented, In addition, the concomitant integration and packaging issues, and the potential NASA applications will be discussed.

Nguyen, Hung↗
NASA NTRS2007

NASA Tech Briefs, July 2007

Topics covered include: Miniature Intelligent Sensor Module; "Smart" Sensor Module; Portable Apparatus for Electrochemical Sensing of Ethylene; Increasing Linear Dynamic Range of a CMOS Image Sensor; Flight Qualified Micro Sun Sensor; Norbornene-Based Polymer Electrolytes for Lithium Cells; Making Single-Source Precursors of Ternary Semiconductors; Water-Free Proton-Conducting Membranes for Fuel Cells; Mo/Ti Diffusion Bonding for Making Thermoelectric Devices; Photodetectors on Coronagraph Mask for Pointing Control; High-Energy-Density, Low-Temperature Li/CFx Primary Cells; G4-FETs as Universal and Programmable Logic Gates; Fabrication of Buried Nanochannels From Nanowire Patterns; Diamond Smoothing Tools; Infrared Imaging System for Studying Brain Function; Rarefying Spectra of Whispering-Gallery-Mode Resonators; Large-Area Permanent-Magnet ECR Plasma Source; Slot-Antenna/Permanent-Magnet Device for Generating Plasma; Fiber-Optic Strain Gauge With High Resolution And Update Rate; Broadband Achromatic Telecentric Lens; Temperature-Corrected Model of Turbulence in Hot Jet Flows; Enhanced Elliptic Grid Generation; Automated Knowledge Discovery From Simulators; Electro-Optical Modulator Bias Control Using Bipolar Pulses; Generative Representations for Automated Design of Robots; Mars-Approach Navigation Using In Situ Orbiters; Efficient Optimization of Low-Thrust Spacecraft Trajectories; Cylindrical Asymmetrical Capacitors for Use in Outer Space; Protecting Against Faults in JPL Spacecraft; Algorithm Optimally Allocates Actuation of a Spacecraft; and Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets.

Source record↗
NASA NTRS2012

Dichroic Filter for Separating W-Band and Ka-Band

The proposed Aerosol/Cloud/Ecosystems (ACEs) mission development would advance cloud profiling radar from that used in CloudSat by adding a 35-GHz (Ka-band) channel to the 94-GHz (W-band) channel used in CloudSat. In order to illuminate a single antenna, and use CloudSat-like quasi-optical transmission lines, a spatial diplexer is needed to add the Ka-band channel. A dichroic filter separates Ka-band from W-band by employing advances in electrical discharge machining (EDM) and mode-matching analysis techniques developed and validated for designing dichroics for the Deep Space Network (DSN), to develop a preliminary design that both met the requirements of frequency separation and mechanical strength. First, a mechanical prototype was built using an approximately 102-micron-diameter EDM process, and tolerances of the hole dimensions, wall thickness, radius, and dichroic filter thickness measured. The prototype validated the manufacturing needed to design a dichroic filter for a higher-frequency usage than previously used in the DSN. The initial design was based on a Ka-band design, but thicker walls are required for mechanical rigidity than one obtains by simply scaling the Ka-band dichroic filter. The resulting trade of hole dimensions for mechanical rigidity (wall thickness) required electrical redesign of the hole dimensions. Updates to existing codes in the linear solver decreased the analysis time using mode-matching, enabling the electrical design to be realized quickly. This work is applicable to missions and instruments that seek to extend W-band cloud profiling measurements to other frequencies. By demonstrating a dichroic filter that passes W-band, but reflects a lower frequency, this opens up the development of instruments that both compare to and enhance CloudSat.

Epp, Larry W.↗
NASA NTRS1976

Optical diodes

Research on metal-barrier-metal structures is reviewed. Topics discussed include: demonstration of antenna coupling and rectification characteristics with high resistance evaporated structures at a wavelength of 10 microns; application of these devices to coherent conversion of laser radiation and infrared and optical circuit elements; and comparison of the point-contact type of diode structure and the newly developed photolithographic structures.

Gustafson, T. K.↗
NASA NTRS1973

Diagnostic techniques for measurement of aerodynamic noise in free field and reverberant environment of wind tunnels

Techniques for studying aerodynamic noise generating mechanisms without disturbing the flow in a free field, and in the reverberation environment of the ARC wind tunnel were investigated along with the design and testing of an acoustic antenna with an electronic steering control. The acoustic characteristics of turbojet as a noise source, detection of direct sound from a source in a reverberant background, optical diagnostic methods, and the design characteristics of a high directivity acoustic antenna. Recommendations for further studies are included.

El-Sum, H. M. A.↗
NASA NTRS1982

Far-infrared imaging antenna arrays

A far-infrared monolithic imaging antenna array with diffraction-limited resolution has been demonstrated. The optical system is similar to an oil-immersion microscope, except that the position of the object and the image are interchanged. The array is a series of evaporated silver bow-tie antennas of 75 nm thick, spaced at 310 microns, on a fused-quartz substrate; the bow angle of 60 deg gives an impedance of 150 ohm to match to bismuth microbolometers. The measured responsivity of the array elements is 1-2 V/W at the relatively low bias of 1 mA. Previous measurements have shown that the bolometers are 1/f noise limited up to 100 kHz and that they have a frequency response of 5 MHz. The antenna array should be adequate for far-infrared plasma interferometer measurements.

Neikirk, D. P.↗
NASA NTRS1996

A low-noise micromachined millimeter-wave heterodyne mixer using Nb superconducting tunnel junctions

A heterodyne mixer with a micromachined horn antenna and a superconductor-insulator- superconductor (SIS) tunnel junction as mixing element is tested in the W-band (75-115 GHz) frequency range. Micromachined integrated horn antennas consist of a dipole antenna suspended on a thin Si(3)N(4) dielectric membrane inside a pyramidal cavity etched in silicon. The mixer performance is optimized by using a backing plane behind the dipole antenna to tune out the capacitance of the tunnel junction. The lowest receiver noise temperature of 30 +/- 3 K (without any correction) is measured at 106 GHz with a 3-dB bandwidth of 8 GHz. This sensitivity is comparable to the state-of-the-art waveguide and quasi-optical SIS receivers, showing the potential use of micromachined horn antennas in imaging arrays.

DeLange, Gert↗
NASA NTRS1996

A Low-noise Micromachined Millimeter-Wave Heterodyne Mixer using Nb Superconducting Tunnel Junctions

A heterodyne mixer with a micromachined horn antenna and a superconductor-insulator-superconductor (SIS) tunnel junction as mixing element is tested in the W-band (75-115 GHz) frequency range. Micromachined integrated horn antennas consist of a dipole antenna suspended on a thin Si3N4 dielectric membrane inside a pyramidal cavity etched in silicon. The mixer performance is optimized by using a backing plane behind the dipole antenna to tune out the capacitance of the tunnel junction. The lowest receiver noise temperature of 30 +/- 3 K (without any correction) is measured at 106 GHz with a 3-dB bandwidth of 8 GHz. This sensitivity is comparable to the state-of-the-art waveguide and quasi-optical SIS receivers, showing the potential use of micromachined horn antennas in imaging arrays.

DeLange, Gert↗
NASA NTRS1998

Micromachined Millimeter- and Submillimeter-Wave SIS Heterodyne Receivers for Remote Sensing

A heterodyne mixer with a micromachined horn antenna and a superconductor -insulator-superconductor (SIS) tunnel junction as mixing element is tested in the W-band (75-115 GHz) frequency range. Micromachined integrated horn antennas consist of a dipole antenna suspended on a thin Si3N4 dielectric membrane inside a pyramidal cavity etched in silicon. The mixer performance is optimized by using a backing plane behind the dipole antenna to tune out the capacitance of the tunnel junction. The lowest receiver noise temperature of 30+/-3 K without any correction) is measured at 106 GHz with a 3-dB bandwidth of 8 GHz. This sensitivity is comparable to the state-of-the-art waveguide and quasi-optical SIS receivers, showing the potential use of micromachined horn antennas in imaging arrays.

Hu, Qing↗