Search NASA⌕ Search

SEARCH · Search NASA

Results for “ABSTRACT”

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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

(abstract) A Solar Electric Propulsion Mission to the Moon and Beyond!

The technological development of solar electric propulsion has advanced significantly over the last few years. Mission planners are now seriously studying which missions would benefit most from solar electric propulsion (SEP) and NASA's Solar System Exploration Division is contributing funding to ground and space qualification tests. In response to the impending release of NASA's Announcement of Opportunity for Discovery class planetary missions, we have undertaken a pre-Phase A study of a SEP mission to the Moon. This mission will not only return a wealth of new scientific data but will open up a whole new era of planetary exploration.

solar electric propulsion SEP Moon↗
NASA NTRS1993

(abstract) Monitoring Seasonal State and Mapping Species in Alaskan Taiga Using Imaging Radar as Input to CO(sub 2) Flux Models

Changes in the seasonal CO(sub 2) flux of the boreal forests may result from increased atmospheric CO(sub 2) concentrations and associated atmospheric warming. To monitor this potential change, a combination of remote sensing information and ecophysiological models are required. In this paper we address the use of synthetic aperture radar (SAR) data to provide some of the input to the ecophysiological models: forest type, freeze/thaw state which limits the growing season for conifers, and leaf on/off state which limits the growing season for deciduous species. AIRSAR data collected in March 1988 during an early thaw event and May 1991 during spring breakup are used to generate species maps and to determine the sensitivity of SAR to canopy freeze/thaw transitions. These data are also used to validate a microwave scattering model which is then used to determine the sensitivity of SAR to leaf on/off and soil freeze/thaw transitions. Finally, a CO(sub 2) flux algorithm which utilizes SAR data and an ecophysiological model to estimate CO(sub 2) flux is presented. CO(sub 2) flux maps are generated from which areal estimates of CO(sub 2) flux are derived.

leaf cover boreal forests radar backscatter↗
NASA NTRS1993

(abstract) Generic Modeling of a Life Support System for Process Technology Comparisons

This paper describes a simulation model called the Life Support Systems Analysis Simulation Tool (LiSSA-ST), the spreadsheet program called the Life Support Systems Analysis Trade Tool (LiSSA-TT), and the Generic Modular Flow Schematic (GMFS) modeling technique. Results of using the LiSSA-ST and the LiSSA-TT will be presented for comparing life support systems and process technology options for a Lunar Base and a Mars Exploration Mission.

life support system long-duration missions simulat↗
NASA NTRS1993

(abstract) Monitoring Seasonal Change in Taiga Forests Using ERS-1 SAR Data

Sensitivity of radar backscatter to the dielectric and geometric character of forested regions suggests significant changes in backscatter are expected with season due to freezing temperatures, snow, wind, leaf fall, and drought. The first European Remote Sensing Satellite, ERS-1, offers a unique opportunity to monitor a complete seasonal cycle for the Alaskan taiga forest ecosystem with synthetic aperture radar. During the 3-day repeat Commissioning Phase of ERS-1, from August 1991to December 1991, ERS-1 SAR data were collected in the region of Manley Hot Springs, Alaska, along the Tanana River, west of Fairbanks. In parallel with the SAR data collection, meteorological data from three weather stations positioned in three forest stands were collected continuously along with in situ measurements of the dielectric and moisture properties of the canopy and of ground cover which were collected during each overflight. The in situ data were collected in floodplain forest stands dominated by balsam poplar, white spruce, and black spruce. These results from the Commissioning Phase as well as preliminary results from the 35-day Repeat Phase will be presented.

characteristics geometric characteristics moisture↗
NASA NTRS1993

(abstract) The SIR-C/X-SAR Mission

The Shuttle Imaging Radar-C and X-Band Synthetic Aperture Radar (SIR-C/X-SAR) is a cooperative experiment between the National Aeronautics and Space Administration (NASA), the German Space Agency (DARA), and the Italian Space Agency (ASI). The experiment is the next evolutionary step in NASA's Spaceborne Imaging Radar (SIR) program that began with the Seasat SAR in 1978, and continued with SAR -A in 1981 and SAR-B in 1984. The program will eventually lead to the Earth Observing System (EOS) SAR later in this decade. SIR-C will provide increased capability over Seasat, SIR-A, and SIR-B by acquiring polarimetric images simultaneously at two microwave frequencies: L-band (wavelength 24 cm) and C-band (wavelength 6 cm). X-SAR will operate at X-band (wavelength 3 cm) with VV polarization, resulting in a three-frequency capability. Because radar backscatter is most strongly influenced by objects comparable in size to the radar wavelength, this multifrequency capability will provide information about the Earth's surface over a wide range of scales not discernable with single-frequency experiments. The polarimetric data will yield quantitative information about the surface geometric structure, vegetation dielectric properties, and surface discontinuities. The first SIR-C/X-SAR flight is planned for early in 1994, with two subsequent flights in different seasons to enable data aquisition under different environmental conditions. SIR-C/X-SAR will collect data for a period of 6 to 9 days during each flight. The instrument will be flown in a 57(deg) inclination orbit with a nomimal orbit altitude of 215 km. This altitude will result in a slightly drifting orbit. The latest status of the SIR-C/X-SAR mission and instrument design, science activities, and expected results will be presented.

SIR-C/XSAR radar backscatter surface geometric str↗
NASA NTRS1993

(abstract) The EOS SAR Mission: A New Approach

The goal of the Earth Orbiting System Synthetic Aperture Radar (EOS SAR) program is to help develop the modeling and observational capabilities to predict and monitor terrestrial and oceanic processes that are either causing global change or resulting from global change. Specifically, the EOS SAR will provide important geophysical products to the EOS data set to improve our understanding of the state and functioning of the Earth system. The strategy for the EOS SAR program is to define the instrument requirements based on required input to geophysical algorithms, provide the processing capability and algorithms to generate such products on the required spatial (global) and temporal (3-5 days) scales, and to provide the spaceborne instrumentation with international partnerships. Initially this partnership has been with Germany; currently we are exploring broader international partnerships. A MultiSAR approach to the EOS SAR which includes a number of SARs provided by Japan, ESA, Germany, Canada, and the US in synergistic orbits could be used to attain a truly global monitoring capability using multifrequency polarimetric signatures. These concepts and several options for mission scenarios will be presented.

Earth Observing System radar imaging international↗
NASA NTRS1993

(abstract) Sensitivity to Forest Biomass Based on Analysis of Scattering Mechanism

The estimation of forest biomass on a global scale is an important input to global climate and carbon cycle models. Remote sensing using synthetic aperture radar offers a means to obtain such a data set. Although it has been clear for some time that radar signals penetrate forest canopies, only recently has it been demonstrated that these signals are indeed sensitive to biomass. Inasmuch as the majority of a forest's biomass is in the trunks, it is important that the radar is sensing the trunk biomass as opposed to the branch or leaf biomass. In this study we use polarimetric AIRSAR P- and L-band data from a variety of forests to determine if the radar penetrates to the trunk by examining the scattering mechanism as determined using van Zyl's scattering interaction model, and the levels at which saturation occurs with respect to sensitivity of radar backscatter to total biomass. In particular, the added sensitivity of P-band relative to L-band is addressed. Results using data from the Duke Forest in North Carolina, the Bonanza Creek Experimental Forest in Alaska, Shasta Forest in California, the Black Forest in Germany, the temporate/boreal transition forests in northern Michigan, and coastal forests along the Oregon Transect will be presented.

forest canopy biomass radar scattering mechanism↗
NASA NTRS1993

(abstract) User Support for an MPP, JPL Begins the Process

The issue of training end-users and center staff in the effective utilization of Cray Research computers is a constant, on-going process at most all sites. Problems such as training materials, class frequency, videos, and site-specific information are very important components in this area. Panel members will offer a varied approach to technical training, and CRI will present possible solutions as well.

training Cray staff users approaches↗
NASA NTRS1993

(abstract) Radiophysical Properties of Venusian Impact Craters

An analysis of 222 large (greater than 20-km-diameter) impact craters on Venus using both cycle 1 and cycle 2 Magellan data is being conducted to determine the radiophysical properties (i.e., backscatter cross section, emissivity, reflectivity, rms slope) of the craters and to search for correlations with target region properties and subsequent geological history.

morphology↗
NASA NTRS1993

(abstract)Electron Impact Emission Cross Sections for Modeling UV Auroral and Dayglow Observations of the Upper Atmospheres of Planets

In the upper atmospheres of the Jovian and Terrestrial planets a dominant mechanism for energy transfer occurs through electron collisional processes with neutral species leading to UV radiation. In response to the need for accurate collision cross sections to model spectroscopic observations of planetary systems, JPL has measured in the laboratory emission cross sections and medium resolution spectra of H, H(sub 2), N(sub 2), SO(sub 2), and other important planetary gases.Voyager and International Ultraviolet Explorer (IUE) spacecraft have established that band systems of H(sub 2) and N(sub 2) are the dominant UV molecular emissions in the solar system produced by electron impact. Applications of our data to models of Voyager, IUE, Galileo, and Hubble Space Telescope observations of the planets will be described.

molecular emissions↗
NASA NTRS1993

(abstract) Effects of Radiation and Oxidative Stress on Development and Morphology of Intestinal Cells

Intestinal cells when subjected to oxidative stress or radiation exhibit abnormal nuclear divisions observed as: 1) supernumerary cell divisions in anterior intestinal cells or 2) incomplete nuclear division and the persistence of anaphase bridges between daughter nuclei. Two oxygen sensitive mutants, mev-1 and rad-8 were observed to exhibit spontaneous supernumerary nuclear divisions at low frequency. N2 can be induced to undergo these divisions by treatment with the superoxide dismutase (SOD) inhibitor diethyl dithicarbamate or with the free radical generator methyl viologen. By contrast, the free radical generator bleomycin produces anaphase bridges in N2 intestinal nuclei at high frequency. Intestinal anaphase bridges can be induced by ionizing radiation and their formation is dependent on dose and radiation type.

division↗
NASA NTRS1993

(abstract) 3D Electromagnetic Plasma Particle Simulations

A 3D electromagnetic plasma particle-in-cell code has been developed using the General Concurrent PIC algorithm. The GCPIC algorithm uses a domain decomposition to divide the computation among the processors. Particles must be exchanged between processors as they move. The efficiencies for 1-, 2-, and 3-dimensional partitions of the three dimensional domain are compared, and the algorithm is found to be very efficient even when a large fraction (e.g., 30%) of the particles must be exchanged at every time step. This PIC code has been used to perform simulations of a variety of space plasma physics problems. Results of three applications will be discussed: 1) plasma disturbances induced by moving conducting bodies in a magnetized plasma; 2) plasma plume interactions; and 3) solar wind termination shock.

electromagnetic plasma particles simulations 3D al↗
NASA NTRS1993

(abstract) Mission Operations and Control Assurance: Flight Operations Quality Improvements

Mission Operations and Command Assurance (MO&CA), a recent addition to flight operations teams at JPL. provides a system level function to instill quality in mission operations. MO&CA's primary goal at JPL is to help improve the operational reliability for projects during flight. MO&CA tasks include early detection and correction of process design and procedural deficiencies within projects. Early detection and correction are essential during development of operational procedures and training of operational teams. MO&CA's effort focuses directly on reducing the probability of radiating incorrect commands to a spacecraft. Over the last seven years at JPL, MO&CA has become a valuable asset to JPL flight projects. JPL flight projects have benefited significantly from MO&CA's efforts to contain risk and prevent rather than rework errors. MO&CA's ability to provide direct transfer of knowledge allows new projects to benefit directly from previous and ongoing experience. Since MO&CA, like Total Quality Management (TQM), focuses on continuous improvement of processes and elimination of rework, we recommend that this effort be continued on NASA flight projects.

mission operation flight operations error detectio↗
NASA NTRS1993

(abstract) Infrared Cirrus and Future Space Based Astronomy

A review of the known properties of the distribution of infrared cirrus is followed by a discussion of the implications of cirrus on observations from space. Probable limitations on space observations due to IR cirrus.

cirrus infrared space observations astronomy inter↗
NASA NTRS1993

(abstract) Supernova Remnant and Molecular Clouds

Upon impact of the shockwaves generated by a supernova remnant, molecular gas and the associated dust grains are substantially excited and become prominent sources of infrared emission. Recent studies of such interactions, utilizing the infrared data and information from other wavelengths, have revealed many details of the physical processes in the interstellar medium. In particluar, the understanding of the temperature and ionization structures in the postshock material is helpful in modeling the star-gas cycles in the Galaxy, and probing the circumstances of star formation.

medium molecular gas↗
NASA NTRS1993

(abstract) Galileo NIMS Thermal Observations of Asteroid 951 Gaspra

The Near Infrared Mapping Spectrometer (NIMS) onboard the Galileo spacecraft performed spectral and thermal imaging of asteroid 951 Gaspra during the spacecraft flyby on October 29, 1991. Measurements of the hemispherically averaged temperature on Gaspra as the spacecraft approached the asteroid will also be reported. Differences resulting from other choices for thermophysical parameters in the model will be explored. Similar measurements are currently being planned for the Galileo encounter with asteroid 243 Ida, which will occur in late August of 1993.

asteroid near infrared imaging Galileo Gaspra Ida↗