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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 397 records · Page 22
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NASA NTRS1999

NASA's Earth Observations Program: Past, Present and Future

A presentation will be given at the Annual National Awards and President's Invited Lecture. The event is sponsored by the Associated Scientific and Technical Societies, an organization which serves the interests of 40,000 scientists and engineers all over South Africa. A general presentation will be given on the topic of NASA's Earth Observation Program and will be supplemented with visualizations using the NASA/NOAA Earth Science Electronic theater. Included will be space observations with an eye on southern Africa, including Etosha National Park, Namibia, Okavanga Delta, Botswana, Victoria Falls, Zimbabwe, and Cape Town, the Highveld around Johannesburg, Blyde River Canyon, and the Lowveld of Kruger National Park in South Africa; also included will be some AVHRR imagery of fire occurrence during the dry season, mostly the Miombo woodland of Zambia, Angola, Malawi, and northern Mozambique, supplemented with SeaWiFS imagery for VI, aerosols, clouds, AVHRR fire time series, Landsat TM (and possibly ETM+, if available), and other global data sets. Would also like to include some Terra animations from SVS, including perhaps the launch sequence. The presentation would conclude with some of the ER-2 MAS imagery from Brazil that highlights the capability that we plan to bring to Africa in August 2000.

King, Michael D.↗
NASA NTRS1999

Multi-Spectral Cloud Property Retrieval

Despite numerous studies to retrieve cloud properties using infrared measurements the information content of the data has not yet been fully exploited. In an effort to more fully utilize the information content of infrared measurements, we have developed a multi-spectral technique for retrieving effective cloud particle size, optical depth and effective cloud temperature. While applicable to all cloud types, we begin by validating our retrieval technique through analysis of MS spectral radiances obtained during the SUCCESS field campaign over the ARM SGP CART facility, and compare our retrieval product with lidar and MODIS Airborne Simulator (MAS) measurement results. The technique is then applied to the Nimbus-4 MS infrared spectral measurements to obtain global cloud information.

Carlson, Barbara E.↗
NASA NTRS1997

Improving the MODIS Global Snow-Mapping Algorithm

An algorithm (Snowmap) is under development to produce global snow maps at 500 meter resolution on a daily basis using data from the NASA MODIS instrument. MODIS, the Moderate Resolution Imaging Spectroradiometer, will be launched as part of the first Earth Observing System (EOS) platform in 1998. Snowmap is a fully automated, computationally frugal algorithm that will be ready to implement at launch. Forests represent a major limitation to the global mapping of snow cover as a forest canopy both obscures and shadows the snow underneath. Landsat Thematic Mapper (TM) and MODIS Airborne Simulator (MAS) data are used to investigate the changes in reflectance that occur as a forest stand becomes snow covered and to propose changes to the Snowmap algorithm that will improve snow classification accuracy forested areas.

Klein, Andrew G.↗
NASA NTRS1999

Refinement of Models for VLBI Analysis

Continual refinement of models and estimation methods is an integral part of improving VLBI measurements of Earth orientation and position along with advances in instrumentation and observing strategy. The modeling of the troposphere continues to be challenging with recent improvements in treating the mean gradient and gradient variations affecting the terrestrial reference frame scale and celestial declinations near the current limits of accuracy. Revised models of nutation and solid Earth tides are implemented in CALC 9.0 to conform to the latest IERS Conventions along with other changes to facilitate use by VLBI correlators. Using data since 1995 the celestial reference frame has been extended and improved consistent with the definition and 0.25 mas accuracy limit of the ICRF. The current definition of the VLBI terrestrial reference frame places a floor on the accuracy of station velocities at the 0.4 mm/yr level. The establishment of the IVS (International VLBI Service for Geodesy and Astrometry) in the past year will provide a forum for further improvements of VLBI data analysis.

Ma, C.↗
NASA NTRS1993

Atlas 2 Animation

The Atmospheric Laboratory for Applications and Science-2 (ATLAS-2), was designed to collect data on the relationship between the sun's energy output and Earth's middle atmosphere and how these factors affect the ozone layer. The ATLAS-2 flew on the Space Shuttle Discovery's mission SST-56, launched on April 8, 1993. The videotape consists of an animated tour of the instruments that were included as part of the mission. The first half of the tape shows the various instruments, pointing to each in turn and identifying each by the associated initialisms. The instruments identified were: the Atmospheric Trace Molecule Spectroscopy (ATMOS), Millimeter Wave Atmospheric Sounder (MAS), Shuttle Solar Backscatter Ultraviolet/A (SSBUV/A) spectrometer, Solar Spectrum Measurement (SOLSPEC) instrument, Solar Ultraviolet Irradiance Monitor (SUSIM), Active Cavity Radiometer (ACR) and Solar Constant (SOLCON).) The second half of the animation shows the same tour without the pointing or the identification of the instruments.

Source record↗
NASA NTRS2000

Profiling of Atmospheric Water Vapor from the SSM/T-2 Radiometric Measurements

An advantage of using the millimeter-wave measurements for water vapor profiling is the ability to probe beyond a moderate cloud cover. Such a capability has been demonstrated from an airborne MIR (Millimeter-wave Imaging Radiometer) flight over the Pacific Ocean during an intense observation period of TOGA/COARE (Tropical Ocean Global Atmosphere/ Couple Ocean Atmospheric Response Experiment) in early 1993. A Cloud Lidar System (CLS) and MODIS Airborne Simulator (MAS) were on board the same aircraft to identify the presence of clouds and cloud type. The retrieval algorithm not only provides output of a water vapor profile, but also the cloud liquid water and approximate cloud altitude required to satisfy convergence of the retrieval. The validity of these cloud parameters has not been verified previously. In this document, these cloud parameters are compared with those derived from concurrent measurements from the CLS and AMPR (Advanced Microwave Precipitation Radiometer).

Wang, J. R.↗
NASA NTRS1999

VSOP Monitoring of the Quasar 1928+738

One limitation of the VSOP (VLBI Space Observatory Program) mission is that several famous superluminal sources such as 3C273 cannot be monitored with good uv-coverage throughout the lifetime of the VSOP Mission at regular intervals that are spaced closely enough to follow the evolution in the fine-scale source-structure. The reason for this is that the HALCA spacecraft cannot#observe sources outside certain restricted ranges of sun angle, defined to be the time variable angle between the source and the sun. However sources that lie within 10 degrees of the ecliptic poles can be observed throughout the year and observations are not restricted to narrow temporal windows. Furthermore, the best ground-based uv-coverages are obtained for circumpolar sources and consequently these will be the sources for which the maximum amount of space VLBI data will be obtained with a given ground array. We have began a VSOP monitoring campaign at 5 GHz on the relatively low redshift (z=0.3) superluminal quasar 1928+738 which is both a circumpolar source and lies 10 degrees away from the ecliptic pole. 1928+738 is in the S5 polar cap sample and has been well studied both on the arsecond-scale and mas-scale. 22 GHz observations have shown that the motion of the VLBI components in 1928+738 is inconsistent with simple linear expansion along a fixed position angle (PA) for all components. Indeed, 1928+738 was one of the first sources for which helical jet motion was proposed and it has been further proposed that a massive binary black hole (MBBH) system is responsible for the sinusoidal jet ridge line observed at 22 GHz over a S year period. our VSOP observations are designed to check this proposal.

Murphy, D. W.↗
NASA NTRS2000

Monitoring of Earth Rotation by VLBI

Monitoring Earth rotation with Very Long Baseline Interferometry (VLBI) has unique potential because of direct access to the Celestial Reference System (CRF and Terrestrial Reference System (TRF) and the feasibility of re-analyzing the entire data set. While formal precision of better than 0.045 mas for pole and 0.002 ms for UT 1 has been seen in the best 24-hr data, the accuracy of the Earth Orientation Parameter (EOP) time series as a whole is subject to logistical, operational, analytical and conceptual constraints. The current issues related to the VLBI data set and the CORE program for greater time resolution such as analysis consistency, network jitter and reference frame stability will be discussed.

Ma., Chopo↗
NASA NTRS2000

EOS Terra Validation Program

The EOS Terra mission will be launched in July 1999. This mission has great relevance to the atmospheric radiation community and global change issues. Terra instruments include Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Clouds and Earth's Radiant Energy System (CERES), Multi-Angle Imaging Spectroradiometer (MISR), Moderate Resolution Imaging Spectroradiometer (MODIS) and Measurements of Pollution in the Troposphere (MOPITT). In addition to the fundamental radiance data sets, numerous global science data products will be generated, including various Earth radiation budget, cloud and aerosol parameters, as well as land surface, terrestrial ecology, ocean color, and atmospheric chemistry parameters. Significant investments have been made in on-board calibration to ensure the quality of the radiance observations. A key component of the Terra mission is the validation of the science data products. This is essential for a mission focused on global change issues and the underlying processes. The Terra algorithms have been subject to extensive pre-launch testing with field data whenever possible. Intensive efforts will be made to validate the Terra data products after launch. These include validation of instrument calibration (vicarious calibration) experiments, instrument and cross-platform comparisons, routine collection of high quality correlative data from ground-based networks, such as AERONET, and intensive sites, such as the SGP ARM site, as well as a variety field experiments, cruises, etc. Airborne simulator instruments have been developed for the field experiment and underflight activities including the MODIS Airborne Simulator (MAS) AirMISR, MASTER (MODIS-ASTER), and MOPITT-A. All are integrated on the NASA ER-2 though low altitude platforms are more typically used for MASTER. MATR is an additional sensor used for MOPITT algorithm development and validation. The intensive validation activities planned for the first year of the Terra mission will be described with emphasis on derived geophysical parameters of most relevance to the atmospheric radiation community.

Starr, David↗
NASA NTRS2000

Near-Infrared Interferometric Images of the Solar System Sized Disk Surrounding the Herbig Ae/Be Star MWC 349A

We present images of the Herbig Ae/Be star MWC 349A at 1.65 and 2.27, and 3.08 micrometers, reconstructed from complex visibility data obtained with an aperture masking interferometric technique on the Keck I telescope. These images have an approximately elliptical shape, and are consistent with the expected shape of a nearly edge-on Keplerian disk. Visibility data were fitted with uniform ellipses with major axes 36 +/- 2, 47 +/- 2, and 62 +/- 1 mas, respectively. The axial ratio of the ellipses is approximately 0.5 +/- 0.1, and the major axis is at a position angle of 100 +/- 3 degrees, consistent with the position angle of the dark lane observed previously in the Very Large Array (VLA) radio continuum maps at 8 and 22 GHz, perpendicular to the symmetry axis of the bipolar lobes of H66(alpha) recombination line emission, and consistent with positions of the recombination line maser spots at 1.3 mm. At an assumed distance of 1.2 kpc, the linear sizes of the disk are 44 and 57 AU at 1.65 and 2.2 micrometers, respectively. The disk is the presumed source of ionized material in the bipolar outflow and ultracompact HII region around the star.

Danchi, W.C.↗
NASA NTRS2001

Detection of X-Ray Emission from Galaxies Inside the Bootes Void

We report the X-ray properties of Bootes void galaxies detected by the ROSAT All-Sky Survey (RASS). By searching the fields of 26 radio and 27 emission-line-selected void galaxies, we have detected nine X-ray-emitting void galaxies at greater than 2.7 sigma confidence level. Five of these nine galaxies are in the IRAS subsample. Two of the IRAS galaxies were previously identified in positional cross-correlation studies of the RASS and IRAS Point Source Catalogue sources. Three of the X-ray-emitting galaxies are active galactic nuclei (AGNs; IRAS 14288+5255, Mrk 845, and IRAS 15195+5050), three are emission-line galaxies (PC 1357+4641, CG 547, and CG 922), and the remaining three are of unknown spectral type (IRAS 14500+4804, CG 637, and MAS 15092+3940). The far-infrared flux levels of the AGN sources imply that most of the observed X-ray emissivity is from starburst activity. We have carried out timing and spectral analysis for the Seyfert 1 galaxy Mrk 845. Poor statistics prevents detailed analysis of the remaining sources. Only two galaxies in our sample, BHI 1514+3819 and FSS 1515+3823, were observed during ROSAT pointed observations resulting in a nondetection at the 1 sigma level.

Kim, Chulhee↗
NASA NTRS2001

Application of Remote Sensing to Assess the Impact of Short Term Climate Variability on Coastal Sedimentation

The University of Wisconsin and Louisiana State University have teamed to study the forcing of winter season cold frontal wind systems on sediment distribution patterns and geomorphology in the Louisiana coastal zone. Wind systems associated with cold fronts have been shown to modify coastal circulation and resuspend sediments along the microtidal Louisiana coast. The assessment includes quantifying the influence of cumulative winter season atmospheric forcing (through surface wind observations) from year to year in response to short term climate variability, such as El Nino events. A correlation between winter cyclone frequency and the strength of El Nino events has been suggested. The atmospheric forcing data are being correlated to geomorphic measurements along western Louisiana's prograding muddy coast. Remote sensing data is being used to map and track sediment distribution patterns for various wind conditions. Transferring a suspended sediment concentration (SSC) algorithm to EOS MODIS observations will enable estimates of SSC in case 2 waters over the global domain. Progress in Year 1 of this study has included data collection and analysis of wind observations for atmospheric forcing characterization, a field activity (TX-2001) to collect in situ water samples with co-incident remote sensing measurements from the NASA ER-2 based MODIS Airborne Simulator (MAS) and the EOS Terra based MODerate resolution Imaging Spectroradiometer (MODIS) instruments, aerial photography and of sediment burial pipe field measurements along the prograding muddy Chenier Plain coast of western Louisiana for documenting coastal change in that dynamic region, and routine collection of MODIS 250 in resolution data for monitoring coastal sediment patterns. The data sets are being used in a process to transfer an SSC estimation algorithm to the MODIS platform. Work is underway on assessing coastal transport for the winter 2000-01 season. Water level data for use in a Geomorphic Impact Index, which relates wind energy, water level conditions, and geomorphic change along the microtidal western Louisiana coastline is being assembled.

Moeller, Christopher C.↗
NASA NTRS2001

A Combined HIPPARCOS and Multichannel Astrometric Photometer Study of the Proposed Planetary System of Rho Coronae Borealis

Hipparcos and Multichannel Astrometric Photometer (MAP) observations of rho Coronae Borealis independently display astrometric motion at the period of the proposed extrasolar planetary companion to the star. Individual least-squares fits to each astrometric data set yield independent estimates of the semimajor axis, inclination, and node angle that are in excellent agreement. A combined solution of the Hipparcos and MAP data yields an inclination of 0.5 deg, a node at 30.5 +/- 12.4, and a semimajor axis of 1.66 +/- 0.35 mas, indicating a companion mass of 0.14 +/- 0.05 solar masses over two orders of magnitude greater than the minimum mass for the companion as determined by radial velocity studies. This mass is approximately that of an M dwarf star, the companion cannot be a planetary object.

Gatewood, George↗
NASA NTRS1998

Comparison of the X-Ray and Radio Light Curves of Quasar PKS 1510--089

We present results for the X-ray-bright superluminal AGN PKS 1510-089 (z=0.36) monitored weekly with the Rossi X-Ray Timing Explorer for the past four years in order to study the origin of X-ray emission from this extremely variable blazer. These RXTE data are compared with weekly cm-band flux and polarization observations from the Michigan Diameter telescope, to identify correlated activity and associated frequency-dependent time delays for constraining X-ray emission models; and bimonthly 7mm VLBA total and linearly polarized intensity imaging to identify temporal associations between X-ray events and the ejection of superluminal components and disturbances in the magnetic field, to test if the X-ray energy release is related to changes in the inner jet flow. Both the X-ray (2-20 keV) and radio flux are highly variable on timescales of weeks. The VLBA mas structure is dominated by a bright core with a weak jet; both the ejection of very fast superluminal knots and changes in the fractional polarization and EVPA of the core on timescales of one to four months are identified. Two outbursts in 1997 are well-resolved in both the centimeter and X-ray bands. Both the strong temporal association and the similar outburst shape support a causal relation, and a discrete cross-correlation analysis identifies that the X-ray lags the radio by 16 days during the bursts. Starting in 1998 the behavior changes: the correlation is weaker with the X-ray possibly leading the radio by six days. During the full time window there is a correlation between bands as expected if the radio photons are upscattered to X-ray energies. The time correlations and difference between the flat X-ray spectral index (0.0 <= alpha <= 0.5 where F(sub v) is proportional to v(exp -alpha)), and the mm-wave synchrotron spectrum (alpha = 0.8) are discussed within the framework of viable SSC models.

Aller, M. F.↗
NASA NTRS2002

The Fourier-Kelvin Stellar Interferometer Mission Concept

The Fourier-Kelvin Stellar Interferometer (FKSI) is a mission concept for an imaging interferometer for the mid-infrared spectral region (5-30 microns). FKSI is conceived as a scientific and technological precursor to TPF as well as Space Infrared Interferometric Telescope (SPIRIT), Submillimeter Probe Evolution of Cosmic Structure (SPECS), and Single Aperture for Infrared Observatory (SAFIR). It will also be a high angular resolution system complementary to Next Generation Space Telescope (NGST). The scientific emphasis of the mission is on the evolution of protostellar systems, from just after the collapse of the precursor molecular cloud core, through the formation of the disk surrounding the protostar, the formation of planets in the disk, and eventual dispersal of the disk material. FKSI will also search for brown dwarfs and Jupiter mass and smaller planets, and could also play a very powerful role in the investigation of the structure of active galactic nuclei and extra-galactic star formation. We are in the process of studying alternative interferometer architectures and beam combination techniques, and evaluating the relevant science and technology tradeoffs. Some of the technical challenges include the development of the cryocooler systems necessary for the telescopes and focal plane array, light and stiff but well-damped truss systems to support the telescopes, and lightweight and coolable optical telescopes. The goal of the design study is to determine if a mid-infrared interferometry mission can be performed within the cost and schedule requirements of a Discovery class mission. At the present time we envision the FKSI as comprised of five one meter diameter telescopes arranged along a truss structure in a linear non-redundant array, cooled to 35 K. A maximum baseline of 20 meters gives a nominal resolution of 26 mas at 5 microns. Using a Fizeau beam combination technique, a simple focal plane camera could be used to obtain both Fourier and spectral data simultaneously for a given orientation of the array. The spacecraft will be rotated to give sufficient Fourier data to reconstruct complex images of a broad range of astrophysical sources.

Danchi, W. C.↗
NASA NTRS2002

Observations of Overshooting Convective Tops and Dynamical Implications

Convective tops overshooting the tropopause have been suggested in the literature to play an important role in modifying the tropical tropopause. The structure of thunderstorm tops overshooting the tropopause have been difficult to measure due to the intensity of the convection and aircraft safety. This paper presents remote observations of overshooting convective tops with the high-altitude ER-2 aircraft during several of the Tropical Rain Measuring Mission (TRMM) and (Convection and Moisture Experiment) CAMEX campaigns. The ER-2 was instrumented with the down-looking ER-2 Doppler Radar (EDOP), a new dropsonde system (ER-2 High Altitude Dropsonde, EHAD), and an IR radiometer (Modis Airborne Simulator, MAS). Measurements were collected in Florida and Amazonia (Brazil). In this study, we utilize the radar cloud top information and cloud top infrared temperatures to document the amount of overshoot and temperature difference relative to the soundings provided by dropsondes and conventional upsondes. The radar measurements provide the details of the updraft structure near cloud top, and it is found that tops of stronger convective cells can overshoot by 1-2 km and with temperatures 5C colder than the tropopause minimum temperature. The negatively buoyant cloud tops are also evidenced in the Doppler measurements by strong subsiding flow along the sides of the convective tops . These findings support some of the conceptual and modeling studies of deep convection penetrating the tropopause.

Heymsfield, Gerald M.↗
NASA NTRS2002

Program of Research in Flight Dynamics in the JIAFS, George Washington University at NASA Langley Research Center

The program objectives are fully defined in the original proposal entitled 'Program of Research in Flight Dynamics in GW at NASA Langley Research Center,' which was originated March 20, 1975, and in the renewals of the research program from December 1, 2000 to November 30, 2001. The program in its present form includes three major topics: 1) the improvement of existing methods and development of new methods for wind tunnel and flight test data analysis, 2) the application of these methods to wind tunnel and flight test data obtained from advanced airplanes, 3) the correlation of flight results with wind tunnel measurements, and theoretical predictions. The Principal Investigator of the program is Dr. Vladislav Klein. Three Graduate Research Scholar Assistants (K. G. Mas, M. M. Eissa and N. M. Szyba) also participated in the program. Specific developments in the program during the period Dec. 1, 2001 through Nov. 30, 2002 included: 1) Data analysis of highly swept delta wing aircraft from wind and water tunnel data, and 2) Aerodynamic characteristics of the radio control aircraft from flight test.

Klein, Vladislav↗