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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

High-Resolution, Ground-Based Observations of the Lunar Sodium Exosphere During the Lunar Atmosphere and Dust Environment Explorer (LADEE) Mission

We present the first comprehensive set of lunar exospheric line width and line width derived effective temperatures as a function of lunar phase (66° waxing phase to 79° waning phase). Data were collected between November 2013 and May 2014 during six observing runs at the National Solar Observatory McMath-Pierce Solar Telescope by applying high-resolution Fabry-Perot spectroscopy (R ~ 180,000) to observe emission from exospheric sodium (5,889.9509 Å, D2 line). The 3-arc min field of view of the instrument, corresponding to ~336 km at the mean lunar distance (384,400 km), was positioned at several locations off the lunar limb; only equatorial observations taken out to 950 km are presented here. We find the sodium effective temperature distribution to be approximately a symmetric function of lunar phase with respect to full Moon. Within magnetotail passage we find temperatures in the range of 2500-9000 K. For phase angles greater than 40deg we find that temperatures flatten out to ~1700 K.

Subsolar↗
NASA NTRS1974

The lunar atmosphere

In contrast to the earth's atmosphere, the atmosphere of the moon is exceedingly tenuous and appears to consist mainly of noble gases. The solar wind impinges on the lunar surface, supplying detectable amounts of helium, neon and Ar-36. Influxes of solar wind protons and carbon and nitrogen ions are significant, but atmospheric gases containing these elements have not been positively identified. Radiogenic Ar-40 and Rn-222 produced within the moon have been detected. The present rate of effusion of argon from the moon accounts for about 0.4% of the total production of Ar-40 due to decay of K-40 if the average abundance of potassium in the moon is 1000 ppm. Lack of weathering processes in the regolith suggests that most of the atmospheric Ar-40 originates deep in the lunar interior, perhaps in a partially molten core. If so, other gases may be vented along with the argon.

Hodges, R. R., Jr.↗
NASA NTRS1972

Response of lunar atmosphere to volcanic gas releases.

A theory of transport of gases emanating from a source on the lunar surface is developed, in which the distribution of a gas is given by the convolution of the time and space description of its source with a Green's function. Green's functions that represent the impulsive response of vertical and horozontal components of particle flux at the lunar surface are derived. The characteristics of these functions and their dependence on the nature of encounters of gas molecules with the lunar surface are discussed in detail.

Hodges, R. R., Jr.↗
NASA NTRS1972

Cold cathode gage experiment (lunar-atmosphere detector)

A preliminary evaluation of the cold cathode gage experiment which was included in the ALSEP to determine the amount of gas present on the lunar surface is reported. The instrument, electronic circuitry, and deployment are described. The preliminary results are summarized and include temperature history, and variations in gas concentration detected after deployment.

Johnson, F. S.↗
NASA NTRS1973

Helium and hydrogen in the lunar atmosphere

Of the gas species supplied by the solar wind, only helium and hydrogen are light enough to be lost from the moon by Jeans' thermal escape mechanism. To study the behavior of helium and hydrogen, a Monte Carlo technique has been used, in which random ballistic trajectories of individual molecules are traced over a spherical moon. In the computation, a particle is 'created' on the sunlit surface, and the locations of its subsequent encounters with the surface are recorded until it escapes. Global distributions of helium and hydrogen concentrations have been computed, based on the hypothesis that the release of neutral gases from the lunar surface is confined to daytime and is correlated with the solar wind influx. The resulting helium model is in good agreement with the measurements from the Apollo 17 lunar surface mass spectrometer.

Hodges, R. R., Jr.↗
NASA NTRS1972

Radon-222 in the lunar atmosphere.

In 1969 Yeh and Van Allen set upper limits for the alpha-particle emissivity of the moon. The equilibrium surface activity reported by Turkevich et al. (1970) for each alpha active Rn-222 daughter at Mare Tranquillitatis cannot be reconciled with existing diffusion theory. The data, therefore, suggest that earth based diffusion constants are not applicable in the vacuum conditions of the moon, or that there are substantial variations in the uranium content of the moon over relatively small distances.

Brodzinski, R. L.↗
NASA NTRS1988

Observations of sodium in the tenuous lunar atmosphere

Spectra showing the sodium D lines above the moon's bright limb (subsolar point) were obtained at first and last quarters, May 27 and June 7, 1988. The number density at the surface is 57 + or - 20 atoms/cu cm and the scale height is 79 + or - 8 km, compatible with the temperature of the surface. Comparison with the Mercurian density of 26,000 atoms/cu cm reveals an enigma. Despite the apparent general similarity of the surfaces, the sodium densities are in a ratio of about 400. The difference may be attributed to differences in source or loss mechanisms or to some fundamental compositional difference between the two planets. The possibility that the source is rapid diffusion of sodium through Mercury's crust and regolith is discussed, as well as recent observational evidence that Mercury's regolith is of intermediate rock type and may be more sodium-rich than the moon's.

Tyler, Ann L.↗
NASA NTRS2011

LADEE Satellite Modeling and Simulation Development

As human activity on and around the Moon increases, so does the likelihood that our actions will have an impact on its atmosphere. The Lunar Atmosphere and Dust Environment Explorer (LADEE), a NASA satellite scheduled to launch in 2013, will orbit the Moon collecting composition, density, and time variability data to characterize the current state of the lunar atmosphere. LADEE will also test the concept of the "Modular Common Bus" spacecraft architecture, an effort to reduce both development time and cost by designing reusable, modular components for use in multiple missions with similar requirements. An important aspect of this design strategy is to both simulate the spacecraft and develop the flight code in Simulink, a block diagram-style programming language that allows easy algorithm visualization and performance testing. Before flight code can be tested, however, a realistic simulation of the satellite and its dynamics must be generated and validated. This includes all of the satellite control system components such as actuators used for force and torque generation and sensors used for inertial orientation reference. My primary responsibilities have included designing, integrating, and testing models for the LADEE thrusters, reaction wheels, star trackers, and rate gyroscopes.

Adams, Michael↗
NASA NTRS1975

Conference on Interactions of the Interplanetary Plasma with the Modern and Ancient Moon, George Williams College, Lake Geneva, Wis., September 30-October 4, 1974, Proceedings

The papers deal with solar-wind and magnetospheric interactions with the moon, ancient and present-day lunar surface magnetic and electric fields, the dynamics and evolution of the lunar atmosphere, the lunar record of solar radiation, and nonmeteoric transport of lunar surface materials. Topics discussed include bow-shock protons in the lunar environment, energetic ion events during the lunar night, mapping of the lunar surface magnetic field from orbital observations of mirrored electrons, geomagnetic disturbances induced by the moon, the relationship between lunar topography and limb compressions, measurements of lunar sky brightness, atmospheric supply and loss mechanisms on the moon, the nature and composition of the lunar atmosphere, molecular gas species in that atmosphere, and vacuum-UV spectroscopic measurements of the surface properties of lunar materials. Individual items are announced in this issue.

Source record↗
NASA NTRS2013

Overview of the LADEE Ultraviolet-visible Spectrometer: Design, Performance and Planned Operations

The Lunar Atmosphere and Dust Environment Explorer (LADEE) is an orbital lunar science mission currently under development to address the goals of the 2003 National Research Council decadal survey, the Lunar Exploration Analysis Group Roadmap, and the "Scientific Context for Exploration of the Moon" (SCEM) report, and has been recommended for execution by the 2011 Planetary Missions Decadal Survey. The mission s focus is to study the pristine state of the lunar atmosphere and dust environment prior to possible lunar exploration activities by countries, including the United States, China, India, and Japan, among others. Activity on the lunar surface has the potential of altering the tenuous lunar atmosphere, but changing the type and concentration of gases in the atmosphere. Before these activities occur it is important to make measurements of the current lunar atmosphere in its unmodified state. LADEE will determine the composition of the lunar atmosphere and investigate the processes that control its distribution and variability, including sources, sinks, and surface interactions. It will monitor variations in known gases, such as sodium, potassium, argon and helium, and will search for other, as-yet-undetected gases of both lunar and extra-lunar origin. LADEE will also determine whether dust is present in the lunar exosphere, and reveal the processes that contribute to its sources and variability. Launch is planned for August, 2013.

Colaprete, A.↗