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Results for “Optical Properties Polarization”

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 163 records · Page 9
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NASA NTRS1982

Retrieval of aerosol optical characteristics from polarization measurements of reflected solar radiation above the oceans

The reflected near infrared solar radiation observed from space above the oceans is due mainly to the atmosphere scattering, as the ocean surface is nearly black. The molecular Rayleigh contribution is also minimized at infrared wavelengths and it can be evaluated. It is shown that the degree of polarization is much more sensitive to the aerosol properties than the radiance. Measurements of polarization at two wavelengths and with an angular scanning are simulated and an inversion algorithm is proposed. It aims at finding an 'equivalent aerosol model', which reproduces the optical thickness and the asymmetry factor of the actual aerosol at all wavelengths in the solar spectrum.

Santer, R.↗
NASA NTRS1998

Constitutive Modeling of the Mechanical Properties of Optical Fibers

Micromechanical modeling of the composite mechanical properties of optical fibers was conducted. Good agreement was obtained between the values of Young's modulus obtained by micromechanics modeling and those determined experimentally for a single mode optical fiber where the wave guide and the jacket are physically coupled. The modeling was also attempted on a polarization-maintaining optical fiber (PANDA) where the wave guide and the jacket are physically decoupled, and found not to applicable since the modeling required perfect bonding at the interface. The modeling utilized constituent physical properties such as the Young's modulus, Poisson's ratio, and shear modulus to establish bounds on the macroscopic behavior of the fiber.

Moeti, L.↗
NASA NTRSDate not supplied

Column Optical Depth (COD) Derived from CALIOP Ocean Surface Returns

The Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) on board the Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite has been making near-global measurements of clouds and aerosols since mid-June 2006. Among the properties reported in CALIPSO data products are estimates of total column optical depth (COD) obtained by integrating the retrieved extinction coefficients of detected particulates (i.e., aerosols and clouds) from 36 km to the surface. However, due to algorithm detection limits and instrument sensitivities, particulates can go undetected when the particulate loading is especially diffuse or in regions where the signal is attenuated by over-lying layers. Because extinction is not calculated where features are not detected, these undetected particulates can introduce low biases into the reported COD. Lidar ratio assumptions used in the extinction retrievals can also introduce errors. To minimize these biases, future releases of the CALIPSO lidar data products will implement an ocean-derived column optical depth (ODCOD) retrieval. The following paper briefly describes the algorithm, the current status of the algorithm development and verification efforts, and preliminary comparisons to col-located COD estimates derived using other retrieval schemes and obtained from other sensors.

Robert A Ryan↗
NASA NTRS2015

Sensitivity Study of Ice Crystal Optical Properties in the 874 GHz Submillimeter Band

Testing of an 874 GHz submillimeter radiometer on meteorological satellites is being planned to improve ice water content retrievals. In this paper we study the optical properties of ice cloud particles in the 874 GHz band. The results show that the bulk scattering and absorption coefficients of an ensemble of ice cloud particles are sensitive to the particle shape and effective diameter, whereas the latter is also sensitive to temperature. The co-polar back scattering cross-section is not sensitive to particle shape, temperature, and the effective diameter in the range of 50200 m.

ice↗
NASA NTRS1998

Validation of POLDER/ADEOS data using a ground-based lidar network: Preliminary results for semi-transparent and cirrus clouds

At mid and tropical latitudes, cirrus clouds are present more than 50% of the time in satellites observations. Due to their large spatial and temporal coverage, and associated low temperatures, cirrus clouds have a major influence on the Earth-Ocean-Atmosphere energy balance through their effects on the incoming solar radiation and outgoing infrared radiation. At present the impact of cirrus clouds on climate is well recognized but remains to be asserted more precisely, for their optical and radiative properties are not very well known. In order to understand the effects of cirrus clouds on climate, their optical and radiative characteristics of these clouds need to be determined accurately at different scales in different locations i.e. latitude. Lidars are well suited to observe cirrus clouds, they can detect very thin and semi-transparent layers, and retrieve the clouds geometrical properties i.e. altitude and multilayers, as well as radiative properties i.e. optical depth, backscattering phase functions of ice crystals. Moreover the linear depolarization ratio can give information on the ice crystal shape. In addition, the data collected with an airborne version of POLDER (POLarization and Directionality of Earth Reflectances) instrument have shown that bidirectional polarized measurements can provide information on cirrus cloud microphysical properties (crystal shapes, preferred orientation in space). The spaceborne version of POLDER-1 has been flown on ADEOS-1 platform during 8 months (October 96 - June 97), and the next POLDER-2 instrument will be launched in 2000 on ADEOS-2. The POLDER-1 cloud inversion algorithms are currently under validation. For cirrus clouds, a validation based on comparisons between cloud properties retrieved from POLDER-1 data and cloud properties inferred from a ground-based lidar network is currently under consideration. We present the first results of the validation.

Chepfer, H.↗
NASA NTRS1984

Regularized Monte-Carlo calculations of the optical polarization induced by scattering in X-ray binaries

The results of regularized Monte Carlo calculations of the optical polarization Stokes parameters expected as a result of scattering from gas streams or accretion wakes in close binary systems whose properties resemble those of X-ray binaries are presented. The physical processes occurring in the system are represented by a model which follows a selected sample of individual photon paths from each emitting element on the surface of the primary to the photon's detection at earth. The result represents the variations in the intensity from each individual emitting element caused by the effects of limb darkening, gravity darkening, and variation in the projected area of the emitting element as seen from the scattering element.

Dolan, J. F.↗
NASA NTRSDate not supplied

Goniometric and Polarized Imaging Spectroscopic Lab Measurements of Spacecraft Materials

To better characterize the spectral response of common spacecraft materials, the following laboratory measurements are presented to support the Space Situational Awareness community in the analysis of remotely sensed observational data. Of interest is classifying material reflective properties using directional reflectance spectroscopy and spatially resolved polarized imaging spectroscopy, allowing laboratory data to be applicable to ground-based optical telescope observations. The team acquired a typical CubeSat solar panel and a sample of multi-layer insulation (MLI) commonly used on spacecraft for initial measurements. The directional spectral data were collected at the Goniometer of the Rochester Institute of Technology (GRIT) laboratory with a lab and field goniometer incorporating two AnalyticalSpectral Device (ASD) spectrometers, a small Lab sphere integrating sphere also paired with an ASD spectrometer, and a Headwall micro-Hyperspec E-Series imaging spectrometer with an adjustable linear polarizer. The goniometer measures spectral bi-directional reflectance factor (BRF) data over a broad range from 350−2500 nm at 1 nm spacing with 3 nm spectral resolution in the visible and near infrared and 8 nm in the shortwave infrared. With the same spectral capabilities, the integrating sphere measures hemispherical-directional reflectance (HDR) in a 45◦-nadir configuration. The Headwall imager covers a spectral range from 400−1000 nm with 1.6 nm spectral resolution.Our initial BRF measurements show interference effects for both materials typically observed with thin films and high infrared reflectivity. In contrast, the interference effects are not present in the HDR measurements of the MLI likely due to the interference effects being averaged out over the reflecting hemisphere. Spatially resolved polarization ratio maps show variability across the materials due to the varying surface structure. We outline a plan for expanding our analysis to a broader range of materials to characterize their directional reflectance spectroscopy.

Chris H. Lee↗
NASA NTRS1975

Focusing crystal polarimeter designed for X-ray polarimetry - Construction and performance

A method for the construction of a graphite crystal polarimeter designed for measuring linear polarization of X-ray continuum sources is described. The dependence of reflected intensity upon the polarization direction of the incident beam at Bragg angles of 45 deg is used to measure the polarization. The particular instrument described was designed for a satellite X-ray polarimeter. By using a focusing parabolic surface instead of a nonfocusing flat crystal, the signal-to-background ratio is improved by a factor of 30 as compared to a flat crystal polarimeter of the same effective area. The focusing properties of the reflector were tested both optically and with X-rays. The performance of the instrument as a polarimeter was tested with a continuum X-ray source of small polarization, which was independently measured by a single flat crystal polarimeter. The agreement between the two measurements is excellent, indicating that the instrument can measure polarizations as low as 0.3%.

Toraskar, J. R.↗
NASA NTRS2009

NASA Tech Briefs, July 2009

Topics covered include: Dual Cryogenic Capacitive Density Sensor; Hail Monitor Sensor; Miniature Six-Axis Load Sensor for Robotic Fingertip; Improved Blackbody Temperature Sensors for a Vacuum Furnace; Wrap-Around Out-the-Window Sensor Fusion System; Wide-Range Temperature Sensors with High-Level Pulse Train Output; Terminal Descent Sensor Simulation; A Robust Mechanical Sensing System for Unmanned Sea Surface Vehicles; Additive for Low-Temperature Operation of Li-(CF)n Cells; Li/CFx Cells Optimized for Low-Temperature Operation; Number Codes Readable by Magnetic-Field-Response Recorders; Determining Locations by Use of Networks of Passive Beacons; Superconducting Hot-Electron Submillimeter-Wave Detector; Large-Aperture Membrane Active Phased-Array Antennas; Optical Injection Locking of a VCSEL in an OEO; Measuring Multiple Resistances Using Single-Point Excitation; Improved-Bandwidth Transimpedance Amplifier; Inter-Symbol Guard Time for Synchronizing Optical PPM; Novel Materials Containing Single-Wall Carbon Nanotubes Wrapped in Polymer Molecules; Light-Curing Adhesive Repair Tapes; Thin-Film Solid Oxide Fuel Cells; Zinc Alloys for the Fabrication of Semiconductor Devices; Small, Lightweight, Collapsible Glove Box; Radial Halbach Magnetic Bearings; Aerial Deployment and Inflation System for Mars Helium Balloons; Steel Primer Chamber Assemblies for Dual Initiated Pyrovalves; Voice Coil Percussive Mechanism Concept for Hammer Drill; Inherently Ducted Propfans and Bi-Props; Silicon Nanowire Growth at Chosen Positions and Orientations; Detecting Airborne Mercury by Use of Gold Nanowires; Detecting Airborne Mercury by Use of Palladium Chloride; Micro Electron MicroProbe and Sample Analyzer; Nanowire Electron Scattering Spectroscopy; Electron-Spin Filters Would Offer Spin Polarization Greater than 1; Subcritical-Water Extraction of Organics from Solid Matrices; A Model for Predicting Thermoelectric Properties of Bi2Te3; Integrated Miniature Arrays of Optical Biomolecule Detectors; A Software Rejuvenation Framework for Distributed Computing; Kurtosis Approach to Solution of a Nonlinear ICA Problem; Robust Software Architecture for Robots; R4SA for Controlling Robots; Bio-Inspired Neural Model for Learning Dynamic Models; Evolutionary Computing Methods for Spectral Retrieval; Monitoring Disasters by Use of Instrumented Robotic Aircraft; Complexity for Survival of Living Systems; Using Drained Spacecraft Propellant Tanks for Habitation; Connecting Node; and Electrolytes for Low-Temperature Operation of Li-CFx Cells.

Source record↗
NASA NTRS1985

Analysis of the new polarimeter for the Marshall Space Flight Center vector magnetograph

The magnetograph was upgraded in both electronic control of the magnetograph hardware and in the polarization optics. The problems associated with the orignal polarimeter were: (1) field of view errors associated with the natural birefringence of the KD*P crystals; (2.) KD*P electrode failure due to the halfwave dc voltage required in one of the operational sequences; and (3) breakdown of the retardation properties of some KD*Ps when exposed to a zero to halfwave modulation (DC) scheme. The new polarimeter gives up the flexibility provided by two variable waveplates to adjust the retardances of the optics for a particular polarization measurement, but solves the problems associated with the original polarimeter. With the addition of the quartz quarterwave plates, a new optical alignment was developed to allow the remaining KD*P to correct for errors in the waveplates. The new optical alignment of the polarimeter is prescribed. The various sources of error, and how those errors are minimized so that the magnetograph can look at the transverse field in real time are discussed.

West, E. A.↗
NASA NTRS1978

Stratospheric Aerosol Measurement (SAM 2) experiment

The Stratospheric Aerosol Measurement 2 (SAM 2) is used to map the concentration and optical properties of stratospheric aerosols as a function of altitude, latitude, and longitude. The vertical distribution of the stratospheric aerosols in the polar regions of both hemispheres is provided.

Mccormick, M. P.↗
NASA NTRS1983

Picosecond measurements using photoacoustic detection

A report is presented of experimental results on picosecond time-resolved photoacoustic measurements of excited-state lifetimes, cross sections, and polarization properties for organic dye molecules in solution, using a new technique in which the total photoacoustic impulse produced by two ultrashort optical pulses with variable time delay between them is detected. The picosecond photoacoustic detection technique reported here appears to be a promising new way to observe weak excited-state cross sections and to perform picosecond lifetime measurements in a large variety of weakly absorbing and/or nonfluorescing atomic and molecular systems.

Heritier, J.-M.↗
NASA NTRS2001

Ocean Color Optical Property Data Derived from OCTS and POLDER: A Comparison Study

We describe our efforts in studying and comparing the ocean color data derived from the Japanese Ocean Color and Temperature Scanner (OCTS) and the French Polarization and Directionality of the Earth's Reflectances (POLDER). OCTS and POLDER were both on board Japan's Sun-synchronous Advanced Earth Observing Satellite (ADEOS-1) from August 1996 to June 1997, collecting about 10 months of global ocean color data. This provides a unique opportunity for developing methods and strategies for the merging of ocean color data from multiple ocean color sensors. In this paper, we describe our approach in developing consistent data processing algorithms for both OCTS and POLDER and using a common in situ data set to vicariously calibrate the two sensors. Therefore, the OCTS and POLDER-measured radiances are effectively bridged through common in situ measurements. With this approach in processing data from two different sensors, the only differences in the derived products from OCTS and POLDER are the differences inherited from the instrument characteristics. Results show that there are no obvious bias differences between the OCTS and POLDER-derived ocean color products, whereas the differences due to noise, which stem from variations in sensor characteristics, are difficult to correct. It is possible, however, to reduce noise differences with some data averaging schemes. The ocean color data from OCTS and POLDER can therefore be compared and merged in the sense that there is no significant bias between two.

Wang, Menghua↗
NASA NTRS2003

Measurement of Characteristics of Micron Size Individual Dust Particles of Astrophysical Interest

A laboratory facility for levitating single isolated dust particles in an electrodynamic balance has been developed at NASA's Marshall Space Flight Center for conducting studies of the physical and optical properties of the analogs of interstellar and interplanetary dust grains of 0.2-20 micron size under controlled pressures/temperatures simulating astrophysical environments. We plan three classes of experiments using this facility: (1) Charge characteristics of micron size single dust grains: The photoelectric efficiencies, yields, and equilibrium potentials when exposed to UV radiation found from these measurements will provide much-needed photoelectric emission data for individual dust particles; (2) Infrared optical properties of dust particles: Specifically, we will determines the complex refractive indices, the extinction coefficients, the scattering phase functions, and the polarization properties of single dust grains of interest in interstellar environments, in the 1- 25 micron spectral region; (3) Condensation experiments to investigate the deposition of volatile gases on colder nucleated particles in dense interstellar clouds and lower planetary atmospheres: The measured data will permit determination of the sticking efficiencies of volatile gases of astrophysical interest. Brief descriptions of the experimental setup for the last two classes of experiments will be given. We will present results of measurements of photoelectric emission using 0.2-6.6 micron size silica particles exposed to UV radiation at 120-200 nm and also results of radiation pressure measurements using the same size silica particles and laser light at 5320 Angstrom.

Craven, P. D.↗
NASA NTRS1993

Optical properties and emissivities of liquid metals and alloys

This paper presents the results from our on-going program to investigate the optical properties of liquid metals and alloys at elevated temperatures. Ellipsometric and polarimetric techniques have been used to investigate the optical properties of materials in the 1000 - 3000 K temperature range and in the 0.3 - 0.1 mu m wavelength range. The ellipsometric and polarimetric techniques are described and the characteristics of the instruments are presented. The measurements are conducted by reflecting a polarized laser beam from an electromagnetically levitated liquid metal or alloy specimen. A Rotating Analyzer Ellipsometer (RAE) or a four-detector Division-of-Amplitude Photopolarimeter (DOAP) is used to determine the polarimetric properties of the light reflected at an angle of incidence of approximately 68 deg. Optical properties of the specimen which are calculated from these measurements include the index of refraction, extinction coefficient, normal spectral emissivity, and spectral hemispherical emissivity. These properties have been determined at various wavelengths and temperatures for liquid Ag, Al, Au, Cu, Nb, Ni, Pd, Pt, Si, Ti, Ti-Al alloys, U, and Zr. We also describe new experiments using pulsed-dye laser spectroscopic ellipsometry for studies of the wavelength dependence of the emissivities and optical properties of materials at high temperature. Preliminary results are given for liquid Al. The application of four-detector polarimetry for rapid determination of surface emissivity and true temperature is also described. Characteristics of these devices are presented. An example of the accuracy of this instrument in measurements of the melting point of zirconium is illustrated.

Krishnan, Shankar↗
NASA NTRS1989

On the diurnal variation of noctilucent clouds

The relationship between nuctilucent clouds (NLC), which are observed from the ground usually within 2 or 3 hrs of local midnight, and the polar mesospheric clouds (PMC), which are observed by satellites in full daylight, as well as the reason for the differences in their optical properties and their observed heights are investigated. Based on a suggestion that these differences can be attributed to a diurnal variation in the properties of a single type of cloud, two published models of the diurnal and semidiurnal variations of temperature, vertical wind speed, and eddy diffusion coefficient at high latitude to simulate the evolution of ice clouds over a 24-hr period. The results show that the minimum in temperature at about 2000 hours LT causes a sharp maximum in scattered brightness to occur about 1 hour before local midnight, with up to a factor of 7 variation in cloud brightness between noon and midnight. It is noted, however, that considerable uncertainties exist in these tidal models.

Jensen, Eric↗
NASA NTRS2011

Titan Haze

The Titan haze exerts a dominating influence on surface visibility and atmospheric radiative heating at optical and near-infrared wavelengths and our desire to understand surface composition and atmospheric dynamics provides a strong motivation to study the properties of the haze. Prior to the Cassini/Huygens missions the haze was known to be global in extent, with a hemispheric contrast asymmetry, with a complicated structure in the polar vortex region poleward of about 55 deg latitude, and with a distinct layer near 370 km altitude outside of the polar vortex at the time of the Voyager 2 flyby. The haze particles measured by the Pioneer and Voyager spacecraft were both highly polarizing and strongly forward scattering, a combination that seems to require an aggregation of small (several tens of nm radius) primary particles. These same properties were seen in the Cassini orbiter and Huygens Probe data. The most extensive set of optical measurements were made inside the atmosphere by the Descent Imager/Spectral Radiometer (DISR) instrument on the Huygens Probe. At the probe location as determined by the DISR measurements the average haze particle contained about 3000 primary particles whose radius is about 40 nm. Three distinct vertical regions were seen in the DISR data with differing particle properties. Refractive indices of the particles in the main haze layer resemble those reported by Khare et al. between O.3S and about 0.7 micron but are more absorbing than the Khare et al. results between 0.7 micron and the long-wavelength limit of the DISR spectra at 1.6 micron. These and other results are described by Tomasko et al., and a broader summary of results was given by Tomasko and West,. New data continue to stream in from the Cassini spacecraft. New data analyses and new laboratory and model results continue to move the field forward. Titan's 'detached' haze layer suffered a dramatic drop in altitude near equinox in 2009 with implications for the circulation and seasonal change in the stratosphere. The book chapter associated with this talk will also present new material on thermal-infrared data analysis and on new developments in laboratory work and haze microphysical modeling.

Anderson, Carrie M.↗
NASA NTRS2005

Accretion Flows in Magnetic White Dwarf Systems

We received Type A and B funding under the NASA Astrophysics Data Program for the analysis and interpretation of hard x-ray data obtained by the Rossi X-ray Timing Explorer and other NASA sponsored missions for Intermediate Polars (IPS) and Polars. For some targets, optical data was available. We reduced and analyzed the X-ray spectra and the X-ray and optical (obtained at the Cerro Tololo Inter-American Observatory) timing data using detailed shock models (which we constructed) to place constraints on the properties of the accreting white dwarfs, the high energy emission mechanisms of white dwarfs, and the large-scale accretion flows of Polars and IPS. IPS and Polars are white dwarf mass-transfer binaries, members of the larger class of cata,clysmic variables. They differ from the bulk of the cataclysmic variables in that they contain strongly magnetic white dwarfs; the white dwarfs in Polars have B, = 7 to 230 MG and those in IPS have B, less than 10 MG. The IPS and Polars are both examples of funneled accretion flows in strong magnetic field systems. The IPS are similar to x-ray pulsars in that accretion disks form in the systems which are disrupted by the strong stellar magnetic fields of the white dwarfs near the stellar surface from where the plasma is funneled to the surface of the white dwarf. The localized hot spots formed at the footpoints of the funnels coupled with the rotation of the white dwarf leads to coherent pulsed x-ray emission. The Polars offer an example of a different accretion topology; the magnetic field of the white dwarf controls the accretion flow from near the inner Lagrangian point of the system directly to the stellar surface. Accretion disks do not form. The strong magnetic coupling generally leads to synchronous orbital/rotational motion in the Polars. The physical system in this sense resembles the Io/Jupiter system. In both IPS and Polars, pulsed emission from the infrared to x-rays is produced as the funneled flows merge onto the white dwarfs through the formation of strong radiating shock waves. A comparative study of the IPS and Polars can elucidate the primary effects of the magnetic fields on the dynamics and thermodynamics in accreting white dwarf systems.

Imamura, James N.↗