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At least 325 records · Page 18

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NASA NTRS1976

On the source of the ancient lunar magnetic field

Analysis of the returned samples, surface observations, and the orbital surveys reveal the presence of a widespread magnetism on the lunar surface but no global field. In the light of Runcorn's proof that internally generated fields do produce magnetization patterns in a spherical crust whose magnetic field lines are confined to within the crust, the above fact is explained in terms of an ancient lunar dynamo which magnetized the lunar crust and then disappeared. The possibility of ancient uniform magnetization by an external field is ruled out, for such magnetization would have been erased as the moon warmed up due to radioactive decay. Although the terrestrial field model is consistent with the measurements, this possibility is also ruled out, because the moon would have had to remain close to earth for about one billion years. The direction of the present magnetization is not predominantly north-south, but is radial and east-west, a fact explained by the assumption that the ancient lunar magnetic dipole moment was not along the present rotation axis.

Russell, C. T.↗

NASA NTRS1976

The role of automatic control in future interplanetary spaceflight

The paper reviews the guidance and automatic control techniques used in previous U.S. and Soviet lunar and planetary exploration spacecraft, and examines the objectives and requirements of potential future interplanetary missions from the viewpoint of their further demands on automatic control technology. These missions include the Venus orbital imaging radar mission, the Pioneer Mars penetrator mission, the Mars surface sample return mission, Pioneer Saturn/Uranus/Titan probe missions, the Mariner Jupiter orbiter with daughter satellite, and comet and asteroid missions.

Scull, J. R.↗

NASA NTRS1976

Ferromagnetic-superparamagnetic granulometry of lunar surface materials

A technique of magnetic granulometry is applied to previously reported data for the temperature dependence of isothermal remanent magnetization (IRM) in 13 lunar surface samples, including three soils. Observed increases in IRM with decreasing temperature are attributed to changes from superparamagnetic to single-domain types of behavior for fine metallic-iron particles. Based on this hypothesis, the temperature dependence of IRM in the examined samples is analyzed to obtain particle-size distributions over the range of mean diameters from 30 to 130 A. It is found that the distribution functions for the soils and a low-grade breccia vary as the inverse square of particle volume and that the distributions for recrystallized breccias and igneous rocks apparently peak about mean values.

Schwerer, F. C.↗

NASA NTRS1977

Using the Shuttle for future advanced planetary missions

Advantages of using the STS for advanced planetary missions are considered. Several factors are analyzed with relation to a proposed exploration of the Jupiter System. Information relating to a Martian expedition for retrieving surface samples and also calculations pertaining to a landing on Titan are presented. The components of the suggested Jupiter System exploration facility include an orbiter, subsatellite, deep probes, Callisto lander, Io lander, and rough landers. Data concerning the STS injection mass possibilities and Ganymede orbiter mass potential are provided.

Friedman, L. D.↗

NASA NTRS1977

Quasi-microscope concept for planetary missions

Viking lander cameras have returned stereo and multispectral views of the Martian surface with a resolution that approaches 2 mm/lp in the near field. A two-orders-of-magnitude increase in resolution could be obtained for collected surface samples by augmenting these cameras with auxiliary optics that would neither impose special camera design requirements nor limit the cameras field of view of the terrain. Quasi-microscope images would provide valuable data on the physical and chemical characteristics of planetary regoliths.

Huck, F. O.↗

NASA NTRS1977

The Lewis Research Center geomagnetic substorm simulation facility

A simulation facility was established to determine the response of typical spacecraft materials to the geomagnetic substorm environment and to evaluate instrumentation that will be used to monitor spacecraft system response to this environment. Space environment conditions simulated include the thermal-vacuum conditions of space, solar simulation, geomagnetic substorm electron fluxes and energies, and the low energy plasma environment. Measurements for spacecraft material tests include sample currents, sample surface potentials, and the cumulative number of discharges. Discharge transients are measured by means of current probes and oscilloscopes and are verified by a photomultiplier. Details of this facility and typical operating procedures are presented.

Berkopec, F. D.↗

NASA NTRS1978

Modification of the continuous flow diffusion chamber for use in zero-gravity

The design philosophy and performance characteristics of the continuous flow diffusion chamber developed for use in ground-based simulation of some of the experiments planned for the atmospheric cloud physics laboratory during the first Spacelab flight are discussed. Topics covered include principle of operation, thermal control, temperature measurement, tem-powered heat exchangers, wettable metal surfaces, sample injection system, and control electronics.

Keyser, G.↗

NASA NTRS1978

NASA Electric Propulsion Program

The described NASA program is to provide the technology base to meet the U.S. future needs in the area of low thrust, high specific impulse propulsion. An electric propulsion system will be needed to augment the Shuttle-IUS Space Transportation System for space missions involving the exploration of the solar system. Plans exist in this connection for comet and asteroid rendezvous, a Saturn and a Mercury orbiter, and a Mars surface sample return. An analysis has shown that electric propulsion can be used to obtain larger payloads, shorter trip times, more mission flexibility, and less complicated trajectories. In addition, electric propulsion has also potential uses for earth orbital missions. Attention is given to the auxiliary propulsion technology program which is to develop a one millipound electron bombardment thrust system, a baseline program concerned with a 3 kilowatt thrust system, ion thruster research, magnetoplasmadynamic thruster research and evaluation, and the use of a mass driver as a reaction mass propulsion system.

Hudson, W. R.↗

NASA NTRS1978

Advanced planetary studies

Eleven study tasks are described and key results are discussed for the following: advanced planning activity; cost estimation research; planetary missions performance handbooks-revisions; multiple discipline science assessment; asteroid workshop; galilean lander mission strategies; asteroid exploration study; ion drive transport capabilities; Mars strategy study; Venus surface sample return; and ion drive/solar sail assessment study.

Source record↗

NASA NTRS1978

Information extraction from digital images of the earth and the planets

An overview is presented of recent developments at the JPL Image Processing Laboratory which emphasize the utilization of a digital computer to automate the process of information extraction from digital imagery. Consideration is given to: (1) the analysis of Viking Orbiter stereo imagery to determine elevation profiles of the Mars surface, (2) the use of Viking Lander stereo imagery to determine nonhazardous surface sample acquisition strategies, (3) the correlation of Landsat imagery with geographically referenced cultural data to determine land use trends, and (4) the generation of mosaics using digital computer techniques.

Green, W. B.↗

NASA NTRS1978

Nature of the gases released from lunar rocks and soils upon crushing

Qualitative and quantitative analyses of inorganic gases released from lunar basalts, breccias and soils by crushing have been performed in an apparatus which consists of a piston operating in a stream of purified He and a dual-column gas chromatograph equipped with He-ionization detectors. The apparatus eliminates the problem of adsorption of the released gases by fresh sample surfaces generated by crushing. Upper concentration levels for nitrogen, H2, CH4, O2 and other gases released from crushed basalts are reported. A direct correlation is established between the amount of nitrogen released from lunar soils by crushing and the lunar soil maturity indicator proposed by Morris (1976).

Gibson, E. K., Jr.↗

NASA NTRS1979

Measurement of chlorophyll a fluorescence with an airborne fluorosensor

Phytoplankton biomass and diversity among various algal species are important for marine productivity assessments. The spatial heterogeneity of phytoplankton in coastal and estuarine environments complicates estimates of total biomass using conventional surface sampling techniques. Since synoptic or near-synoptic data can be quite useful in these studies, this area is a natural focal point for development of remote sensors. However, it is very difficult to sense phytoplankton density and diversity with spacecraft-borne passive sensors primarily because modulation in the signal due to phytoplankton is of the same order as that of atmospheric effects. The same sensors mounted on aircraft may be able to detect and quantify high concentrations of phytoplankton (blooms), but the current lack of knowledge about the spectral reflectance signatures of the major phytoplankton color groups rules out any diversity measurements by this type of sensor. An active fluorosensor mounted on a low-flying aircraft or helicopter is not limited by any of these constraints. A brief survey of the four currently active systems is presented.

Jarrett, O., Jr.↗

NASA NTRS1979

Atmospheric entry systems for advanced Mars missions

A study of estimates of the mass and performance characteristics of entry system designs for advanced Mars missions is presented. The missions were: (1) a Mars Surface Sample Return Mission (MSSR), (2) a Mars Hard Lander, and (3) a Mars Aircraft Mission, and Viking technology or its extensions were used for these entry system conceptual designs. For the MSSR mission, various mission combinations were evaluated including different Mars Ascent Vehicle masses and the use of 2 through 4 stages of the IUS launch vehicle. The constraints for this Mars mission were the Shuttle payload bay geometry limitation and its massive requirements. Requirements for the simple Hard Lander Mission including entry and deceleration, using a parachute and a solid rocket are discussed. A design requirement for the Mars Aircraft Mission to minimize the total entry capsule/aircraft mass by combining entry functions and hardware into the aircraft system was described, and various approaches for supporting the folded aircraft within the aeroshell were examined.

Butts, A. J.↗

NASA NTRS1980

Coordinated aircraft and ship surveys for determining impact of river inputs on great lakes waters. Remote sensing results

The remote sensing results of aircraft and ship surveys for determining the impact of river effluents on Great Lakes waters are presented. Aircraft multi-spectral scanner data were acquired throughout the spring and early summer of 1976 at five locations: the West Basin of Lake Erie, Genesee River - Lake Ontario, Menomonee River - Lake Michigan, Grand River - Lake Michigan, and Nemadji River - Lake Superior. Multispectral scanner data and ship surface sample data are correlated resulting in 40 contour plots showing large-scale distributions of parameters such as total suspended solids, turbidity, Secchi depth, nutrients, salts, and dissolved oxygen. The imagery and data analysis are used to determine the transport and dispersion of materials from the river discharges, especially during spring runoff events, and to evaluate the relative effects of river input, resuspension, and shore erosion. Twenty-five LANDSAT satellite images of the study sites are also included in the analysis. Examples of the use of remote sensing data in quantitatively estimating total particulate loading in determining water types, in assessing transport across international boundaries, and in supporting numerical current modeling are included. The importance of coordination of aircraft and ship lake surveys is discussed, including the use of telefacsimile for the transmission of imagery.

Raquet, C. A.↗

NASA NTRS1980

Isotopically anomalous silver in the Santa Clara and Pinon iron meteorites

The isotopic composition and concentration of Ag and the concentration of Pd have been determined in the Santa Clara and Pinon iron meteorites. It is shown that these meteorites contain isotopically anomalous Ag with an excess of Ag-107 relative to normal Ag, confirming earlier findings. Using an improved procedure for cleaning the sample surface from terrestrial Ag, a new concentration of 1.4 x 10 to the 11th atoms of Ag-109/g meteorite is established which is an order of magnitude below the levels found earlier. As a result ratios of Ag-107/Ag-109 were found which are enriched in Ag-107 by 60 percent to 160 percent. The existence of an excess Ag-107 in these two meteorites, which have high Pd-108/Ag-109 ratios of about 7 x 10 to the 4th is established.

Kaiser, T.↗

NASA NTRS1981

Geological remote sensing: Identification and mapping of rock types for non-renewable resources

Efforts concentrated on developing a technique for relating laboratory spectral reflectance curves of known rocks and vegetation on LANDSAT multispectral images. The techniques involves determination of the laboratory spectral signature of a material of interest and searching a stack of spatially registered multispectral images for materials with the desired spectral signature. Changes in spectral reflectance caused by vegetation cover were also investigated in surface samples from Hawaii.

Adams, J. B.↗

NASA NTRS1980

A polarizer for vacuum ultraviolet

An MgF2 double Rochon prism, useful as a polarizer or analyzer in wavelengths longer than 1300A is described. Measurements of MgF2 transmission and of polarizer angular beam deviation from 1150 to 2900A are presented. The prism is comprised of 2.25 mm, MgF2 depolarizers, optically contacted. At normal incidence, a 4% transmission gain was measured from 6000 to 2200A, compared with air spaced elements. One depolarizer was vibrated to 40 g from 20 to 3500 Hz without deterioration in optical contact. Transmissions below 1400A are not good. In thin samples, surface loss is twice absorption loss in the range 1150 to 1500A. Refraction indices and a computer ray trace were used in processing photographic beam divergence data. If care is taken to remedy scattering effects, the prism is an efficient on-axis polarizer in the 1300 to 3000A range.

Steinmetz, D. L.↗

NASA NTRS1980

Possible rim crest deposits in cores 12027 and 15008 - Some interpretations and problems for future research

Light colored coarse grained soils in the upper parts of cores 12027 and 15008 have a chaotic fabric and abundant bedrock-derived rock fragments. They overlie dark colored, fine grained soils with horizontal fabric and abundant regolith-derived rock fragments. The light colored soils are interpreted to be rim crest deposits associated with the craters seen in the lunar surface sampling photographs. The coarse size, poor sorting and chaotic fabric are believed to have originated by the violent mixing processes which are expected with ejecta deposition. The increase in bedrock-derived particles within the light colored soil can be explained by ejecta from craters that penetrated through or deep into the regolith. The dark soils are believed to predate the craters. Distribution of rock fragments in the material interpreted as rim crest ejecta does not fit a simple model of overturned stratigraphy.

Nagle, J. S.↗