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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

IPL processing of the Mariner 10 images of Mercury

This paper describes the digital processing performed on the images of Mercury returned to earth from Mariner 10. Each image contains considerably more information than can be displayed in a single picture. Several specialized processing techniques and procedures are utilized to display the particular information desired for specific scientific analyses: radiometric decalibration for photometric investigations, high-pass filtering to characterize morphology, modulation transfer function restoration to provide the highest possible resolution, scene-dependent filtering of the terminator images to provide maximum feature discriminability in the regions of low illumination, and rectification to cartographic projections to provide known geometric relationships between features. A principal task was the construction of full disk mosaics as an aid to the understanding of surface structure on a global scale.

Soha, J. M.↗
NASA NTRS1975

Mercury rotation period determined from Mariner 10 photography

The rotation period of Mercury has been determined to be 58.661 days by using high-resolution photography from the Mariner 10 mission. This value matches the period required for 3/2 synchronism with the orbital period (58.6462 days) within the 1-sigma errors assigned and is consistent with the latest values derived from radar and earth-based telescopic observations.

Klaasen, K. P.↗
NASA NTRS1975

Preliminary geologic terrain map of Mercury

A geologic terrain map of Mercury has been constructed by use of the photogeologic methods employed for the moon and Mars. The oldest and most widespread unit, intercrater plains, forms nearly level to rolling surfaces on which are superposed numerous secondary impact craters. This unit may represent a very old surface that predates the last heavy bombardment of the inner planets. The effects of this bombardment are recorded in a second widespread unit, heavily cratered terrain, consisting of closely spaced craters and basins from 30 km to several hundred kilometers in diameter. Units formed by excavation of the 1300-km-diameter Caloris basin are widespread on one hemisphere of the planet. The development of the Caloris basin was followed relatively quickly by emplacement of widespread plains materials, most of which are probably volcanic.

Trask, N. J.↗
NASA NTRS1974

Mercury bombardment ion thrusters - Development status, performance levels, and test history

The present work describes the development status, performance levels, and life test history of 5-cm, 8-cm, and 30-cm mercury bombardment ion thrusters and their respective power processors. A 2.6 kW, 30-cm thruster module and its power processor unit are now available that established the performance required by interplanetary and geosynchronous orbit raising missions. An 8-cm thruster with nominal 4.5 mN thrust level capability has demonstrated a high performance over a wide range of thrust and operational life.

Molitor, J. H.↗
NASA NTRS1974

U.S. solar-electric propulsion planetary mission candidates - Out-of-the-ecliptic, small bodies, and orbiters of Mercury and Saturn

It is pointed out that increasing mission complexity in the case of targets far from earth during the exploration of the solar system will be accompanied by significantly higher propulsive energy requirements. The development of an operational solar-electric propulsion (SEP) system would significantly alter high-energy mission capabilities. The utility of a moderately powered SEP on a set of missions is demonstrated, giving attention to small body missions, out-of-the-ecliptic missions, the problems of a Mercury orbiter mission, and augmented mission requirements in the case of a Saturn orbiter.

Atkins, K. L.↗
NASA NTRS1975

Film boiling of mercury droplets

Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

Baumeister, K. J.↗
NASA NTRS1975

Mercury's helium exosphere

A model He exosphere of Mercury is developed whose source derives from accretion of the small fraction of solar-wind He(++) that is captured by the magnetosphere and absorbed at the planetary surface. The model is based on a lunar analogy whereby the surface is saturated with He. Surface and radial density distributions are derived, and the dayside concentration is determined by requiring that the limb intensity at 584 A equals the observed intensity. To maintain the He exosphere, it is found that only a fraction of the solar-wind He(++) flux intercepted by the magnetosphere need be captured. This corresponds to a total accretion rate of 6.8 by 10 to the 22nd power He(++) ions per sec at the surface, which also represents the upper limit to the total outgassing rate of He from the interior.

Hartle, R. E.↗
NASA NTRS1975

Geothermal hazards - Mercury emission

Enthusiasm for intensified geothermal exploration may induce many participants to overlook a long-term potential toxicity hazard possibly associated with the tapping of magmatic steam. The association of high atmospheric Hg levels with geothermal activity has been established both in Hawaii and Iceland, and it has been shown that mercury can be introduced into the atmosphere from fumaroles, hot springs, and magmatic sources. These arguments, extended to thallium, selenium, and other hazardous elements, underscore the need for environmental monitoring in conjunction with the delivery of magmatic steam to the surface.

Siegel, S. M.↗
NASA NTRS1975

In-flight calibration of the high-gain antenna pointing for the Mariner Venus-Mercury 1973 spacecraft

The methods used to in-flight calibrate the pointing direction of the Mariner Venus-Mercury 1973 spacecraft high gain antenna and the achieved antenna pointing accuracy are described. The overall pointing calibration was accomplished by performing calibration sequences at a number of points along the spacecraft trajectory. Each of these consisted of articulating the antenna about the expected spacecraft-earth vector to determine systematic pointing errors. The high gain antenna pointing system, the error model used in the calibration, and the calibration and pointing strategy and results are discussed.

Hardman, J. M.↗
NASA NTRS1976

Film thickness measurements on five fluid formulations by the mercury squeeze film capacitance technique

The thinning characteristics of five fluids were studied by measuring film thickness as a function of time. The mercury squeeze film capacitance technique was used. All tests were performed at room temperature. The synthetic hydrocarbon plus a nematic liquid crystal, N-(p-methoxybenzylidene)-p-butylaniline, thinned according to a Newtonian model and retained its bulk viscosity. The synthetic hydrocarbon plus a phosphonate antiwear additive and the synthetic hydrocarbon plus n-hexadecanol produced residual thick films. The synthetic hydrocarbon base fluids and the synthetic hydrocarbon plus a paraffinic resin displayed viscosity increases during thinning, but no residual films were formed.

Jones, W. R., Jr.↗
NASA NTRS1976

Interaction of solar wind with Mercury and its magnetic field

A brief review is presented of magnetic field and solar wind electron observations by Mariner 10 spacecraft. The intrinsic magnetic field of the planet Mercury and the implications of such a field for the planetary interior are also discussed.

Ness, N. F.↗
NASA NTRS1975

Earth-type planets (Mercury, Venus, and Mars)

Spacecraft- and Earth-based studies on the physical nature of the planets Mercury, Venus, and Mars are reported. Charts and graphs are presented on planetary surface properties, rotational parameters, atmospheric compositions, and astronomical characteristics.

Marov, M. Y.↗
NASA NTRS1974

Charged particle measurements on a 30-CM diameter mercury ion engine thrust beam

Measurements of both thrust ions and charge exchange ions were made in the beam of a 30 centimeter diameter electron bombardment mercury ion thruster. A qualitative model is presented which describes magnitudes of charge exchange ion formation and motions of these ions in the weak electric field structure of the neutralized thrust beam plasma. Areas of agreement and discrepancy between observed and modeled charge exchange properties are discussed.

Sellen, J. M., Jr.↗
NASA NTRS1975

Mariner-Venus-Mercury optical navigation demonstration - Results and implications for future missions

Optical navigation uses spacecraft television pictures of a target body against a known star background in a process which relates the spacecraft trajectory to the target body. This technology was used in the Mariner-Venus-Mercury mission, with the optical data processed in near-real-time, simulating a mission critical environment. Optical data error sources were identified, and a star location error analysis was carried out. Several methods for selecting limb crossing coordinates were used, and a limb smear compensation was introduced. Omission of planetary aberration corrections was the source of large optical residuals.

Acton, C. H., Jr.↗
NASA NTRS1976

Does Mercury have a molten core

The question of whether or not Mercury could contain a molten metallic core is investigated by studying the possible thermal evolution of a metallic core in that planet. The calculations involve the solution of the equation of heat conduction for a spherically symmetric body with internal heat sources, modifications to take account of the latent heat of fusion as well as the redistribution of radioactive heat sources as a consequence of melting, the terrestrial Fe/U ratio, and a Th/U ratio of 3.7. The temperature profile predicted by the calculations for a period of 4.6 billion years indicates that the inner 1400 km of the core would now be solid while the outer 500 km would be molten. It is emphasized that this result is a direct consequence of a discontinuity in melting temperatures at the core-mantle boundary and that although a dynamo is possible, it would have to be driven mechanically rather than by thermal convection.

Fricker, P. E.↗
NASA NTRS1976

Crater populations in the early history of Mercury

Crater populations on two major geologic units of Mercury have been classified into three morphologic types which characterize their state of degradation. The results indicate that one or more processes either prior to or contemporary with the formation of the 1300-km-diameter Caloris Planitia reduced the population of fresh craters smaller than 70 to 80 km in diameter and totally erased the population of fresh craters smaller than 20 to 30 km.

Guest, J. E.↗
NASA NTRS1976

Inferences from the dynamical history of Mercury's rotation

The history of Mercury's spin angular momentum is reviewed. It is shown that the current nonsynchronous but resonant spin and the nearly zero obliquity place almost no restrictions on the primordial spin state. The only exception comes about from a liquid core-solid mantle interaction which excludes a slow primordial spin concurrent with a large obliquity. The current occupancy of a final evolutionary spin state leads to the description of a scheme by which we can determine the extent of a currently liquid Mercurian core.

Peale, S. J.↗