(abstract) Comparison of the Solar Wind Interaction with Comets Giacobini-Zinner, Halley, and Grigg-Skjellerup
Results from the encounters with comets Giocobini-Zinner, Halley, and Grigg-Skjellerup are reviewed.
comets solar wind encounters models↗
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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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(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↗
(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↗
(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↗
(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↗
(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↗
(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↗
(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↗
(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↗
(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↗
(abstract) System Performance of the Joint Galileo/Mars Observer/Ulysses 1993 Gravitational Wave Experiment
From March 21 to April 11, 1993, the Galileo, Mars Observer, and Ulysses spacecraft were tracked almost continuously in a coincidence experiment to search for low-frequency (~millihertz) gravitational radiation. We report here a first statistical assessment of the noise characteristics of the data, with particular attention to the performance of the radio science instrumentation itself.
gravitational waves radio science noise Doppler ef↗
(abstract) Reddening Measurements using CCD uvby (Stromgren) Photometry
Reddening measurements for interstellar clouds have usually relied on one of two techniques: Star counts or spectro-photometric measurements. We present preliminary results for a technique to determine the extinction using CCD uvby (Stromgren) photometry, without the need to perform special classification of the stars. The method relies on the fact that the uvby system allows two independent measurements of the reddening through the m(sub 1)and c(sub 1) indices to select the true intrensic colors for each star. Using observations from the Burrell Schmidt on Kitt Peak, we find that the technique allows reliable reddening measurements to be made down to at least V=15&supm;.
measurements↗
(abstract) Fundamental Mechanisms of Electrode Kinetics and Alkali Metal Atom Transport at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary
The mechanisms of electrode kinetics and mass transport of alkali metal oxidation and alkali metal cation reduction at the solid electrolyte/porous electrode boundary as well as alkali metal transport through porous metal electrodes has important applications in optimizing device performance in alkali metal thermal to electric converter (AMTEC) cells which are high temperature, high current density electrochemical cells. Basic studies of these processes also affords the opportunity to investigate a very basic electrochemical reaction over a wide range of conditions; and a variety of mass transport modes at high temperatures via electrochemical techniques. The temperature range of these investigations covers 700K to 1240K; the alkali metal vapor pressures range from about 10(sup -2) to 10(sup 2) Pa; and electrodes studied have included Mo, W, Mo/Na(sub 2)MoO(sub 4), W/Na(sub 2)WO(sub 4), WPt(sub x), and WRh(sub x) (1.0 < x < 6.0 ) with Na at Na-beta'-alumina, and Mo with K at K-beta'-alumina. Both liquid metal/solid electrolyte/alkali metal vapor and alkali metal vapor/solid electrolyte/vapor cells have been used to characterize the reaction and transport processes. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes.
electrode kinetics thermal to electric conversion ↗
(abstract) Alkali Metal Diffusion Through Porous Metal Electrodes in AMTEC Cells
The mechanisms of mass transport of an alkali metal through porous metal electrodes in alkali metal thermal-to-electric converter AMTEC cells is important in optimizing these high current density devices, but also affords the opportunity to investigate a variety of simple mass transport modes at high temperatures via electrochemical techniques. We have previously reported evidence of ionic, free molecular flow, and surface transport of sodium in several types of AMTEC electrodes. Quantitative investigations of Na transport through WPt(sub 3.5) via surface or grain boundary diffusion, and K transport through porous Mo electrodes by free molecular flow, over large ranges of temperature have been performed. WPt(sub 3.5) has especially low transport impedance over the 950 to 1200K temperature range. New results are the Na through porous WPt(sub 3.5) and K through porous Mo diffusion rates and mechanisms.
alkali metal mass transport porous metal electrode↗
(abstract) Experimental and Modeling Studies of the Exchange Current at the Alkali Beta'-Alumina/Porous Electrode/Alkali Metal Vapor Three Phase Boundary
The microscopic mechanism of the alkali ion-electron recombination reaction at the three phase boundary zone formed by a porous metal electrode in the alkali vapor on the surface of an alkali beta'-alumina solid electrolyte (BASE) ceramic has been studied by comparison of the expected rates for the three simplest reaction mechanisms with known temperature dependent rate data; and the physical parameters of typical porous metal electrode/BASE/alkali metal vapor reaction zones. The three simplest reactions are tunneling of electrons from the alkali coated electrode to a surface bound alkali metal ion; emission of an electron from the electrode with subsequent capture by a surface bound alkali metal ion; and thermal emission of an alkali cation from the BASE and its capture on the porous metal electrode surface where it may recombine with an electron. Only the first reaction adequately accounts for both the high observed rate and its temperature dependence. New results include crude modeling of simple, one step, three phase, solid/solid/gas electrochemical reaction.
conversion↗
(abstract) An Ada Language Modular Telerobot Task Execution System
A telerobotic task execution system is described which has been developed for space flight applications. The Modular Telerobot Task Execution System (MOTES) provides the remote site task execution capability in a local-remote telerobotic system. The system provides supervised autonomous control, shared control, and teleoperation for a redundant manipulator. The system is capable of nominal task execution as well as monitoring and reflex motion.
robots telerobotics teleoperator autonomous contro↗
(abstract) The Nest Generation of Space Flight Computers
To meet new design objectives for drastic reductions in mass, size, and power consumption, the Flight Computer Development Group at JPL is participating in a design study and development of a light-weight, small-sized, low-power 3-D Space Flight Computer. In this paper, we will present a detailed design and tradeoff study of the proposed computer. We will also discuss a complete design of the multichip modules and their size, weight, and power consumption. Prelimimary thermal models will also be discussed.
space flight computers design power consumption ma↗
(abstract) Galileo Optical Link Takes a Step Towards Deep-Space Optical Communications
The Galileo Optical Experiment (GOPEX) is the first in a series of JPL optical communications experiments that are planned to 1) demonstrate the application of critical concepts, subsystems, and components to optical communications technology, 2) validate optical communications performance models, and 3) improve the conceptual design of a deep-space and near-Earth optical communications network. Such a network is envisioned to be global in extent, and will require construction of optical stations on several continents. Industry can play a role in the development of this new breaking technology by assisting in addressing some of the current technology challenges.
optical communications experiment space communicat↗