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Results for “LUNAR IONOSPHERE”

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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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2021

A theoretical assessment of the feasibility of potential Lunar Reconnaissance Orbiter radio occultation observations of the lunar ionosphere

The existence of a “dense” lunar ionosphere has been controversial for decades. Positive ions produced from the lunar surface and exosphere are inferred to have densities that are.106– 107m−3near the surface and smaller at higher altitudes, yet electron densities derived from radio occultation measurements occasionally exceed these values by orders of magnitude. For example, about 4% of the single-spacecraft radio occultation measurements from Kaguya/SELENE were consistent with peak electron densities of∼3×108m−3. Space plasmas should be neutral on macroscopic scales, so this represents a substantial discrepancy. Additional observations of electron densities in the lunar ionosphere are critical to resolving this long standing paradox. Here we theoretically assess whether radio occultation observations using two-way coherent S-band radio signals from the Lunar Reconnaissance Orbiter (LRO) spacecraft could provide useful measurements of electron densities in the lunar ionosphere. We predict the uncertainty in a single LRO radio occultation measurement of electron density to be∼3×108m−3, comparable to occasional observations by Kaguya/SELENE of a dense lunar ionosphere. Thus an individual profile from LRO is unlikely to reliably detect the lunar ionosphere; however, averages of multiple (∼10) LRO profiles acquired under similar geophysical and viewing conditions should be able to make reliable detections. An observing rate of six ingress occultations per day (∼2000 per year) could be achieved with mini-mal impact on current LRO operations. This rate compares favorably with the 378observations reported from the single-spacecraft experiment on Kaguya/SELENE between November 2007 and June 2009. The large number of observations possible for LRO would be sufficient to permit wide-ranging investigations of spatial and temporal variations in the poorly understood lunar ionosphere. These findings strengthen efforts to conduct such observations with LRO.

Paul Withers↗
NASA NTRS2011

On the Role of Dust in the Lunar Ionosphere

Evidence suggests that electron concentrations above the dayside lunar surface can be significantly higher than expected from either the photo-ionization of exospheric neutrals or any other well-known process. The Luna 19 mission performed dual-frequency radio occultation experiments in order to determine electron column concentrations above the lunar limb as a function of tangent height (shown in the figure below), The resulting electron concentration profiles surprisingly indicated a peak of approx.500-1000/cu cm and scale heights of approx. 10-30 km. It has been suggested that electrically charged exospheric dust could contribute to these electron cnhancemcnts2 , Here we describe how to estimate the electrons produced by photo-charged dust, which is then used to predict electron concentrations from exospheric dust distribution models that are based on the "excess brightness" observed in Apollo 15 coronal photographs. The results indicate that radio occultation measurements likely provide a valuable perspective on the role of dust in the lunar environment.

Stubbs, Timothy J.↗
NASA NTRS1972

Suprathermal ion detector experiment (lunar ionosphere detector)

The highly directional flow of energetic ions down the magnetosheath is described using three different look directions of the three Apollo 15 SIDE instruments. The effects of the interaction of the LM ascent-engine exhaust with the magnetosheath ions observed at the Apollo 15 site are discussed, and a preliminary analysis of the SIDE data for Apollo 12 and 14 is included.

Hills, H. K.↗
NASA NTRS1975

Studies in matter antimatter separation and in the origin of lunar magnetism

A progress report, covering lunar and planetary research is introduced. Data cover lunar ionospheric models, lunar and planetary geology, and lunar magnetism. Wind tunnel simulations of Mars aeolian problems and a comparative study of basaltic analogs of Lunar and Martial volcanic features was discussed.

Barker, W. A.↗
NASA NTRS1975

The lunar terminator ionosphere

The extended ionosphere is seen by the Suprathermal Ion Detector Experiments (SIDE) near the terminator. An analysis of the energy and mass spectra of these ions accelerated by the interplanetary electric field indicates the following: (1) the principal ion species are in the mass per unit charge ranges consistent with neon and argon, (20-28 and 40-44 amu/q); (2) the lunar atmosphere in these mass ranges is distributed exponentially; (3) the terminator region surface number density for Ne-20 is of the order of 10 to the 5th/cu cm; (4) the terminator region lunar surface potential is negative from about 10 to 100 volts; and (5) this potential has a screening length of the order of a kilometer.

Benson, J.↗
NASA NTRS1973

Lunar ion flux and energy

The dynamics of the lunar ionosphere and resulting flux of lunar ions to the lunar surface are reviewed. In the Lunar rest frame, ions formed from the neutral lunar atmosphere are accelerated by the interplanetary electric and magnetic fields. The trajectories of heavier ions are primarily along the electric field; the ion flux is in a direction perpendicular to the solar wind flow, correlated to the orientation of the interplanetary magnetic field, and impacts the surface with energies of tens of electron volts to a few keV. Thus we predict a relatively energetic (compared to thermal energies), highly directional, lunar ion flux but with the possibility that light ions such as hydrogen can execute orbits that return them to portions of the lunar surface not directly exposed to the solar wind. The effects of surface electric and magnetic fields are discussed, as is the ion energy spectrum. We calculate the trapping of atmospheric ions which impact the surface and from this the density of neutral Ar 40 in the lunar atmosphere. We show that using the acceleration model, the lunar atmosphere total neutral number density can be calculated from ion detector data.

Manka, R. H.↗
NASA NTRS1975

The Apollo lunar surface experiment package suprathermal ion detector experiment

A compilation of reports and scientific papers is presented for the following topics: (1) the lunar ionosphere; (2) electric potential of the lunar surface; (3) ion activity on the lunar nightside; (4) bow shock protons; (5) magnetosheath and magnetotail; (6) solar wind-neutral gas cloud interactions at the lunar surface; (7) penetrating solar particles; and (8) rocket exhaust products from Apollo missions. Descriptions and photographs of ion detecting equipment at the lunar sites of Apollo 12, 13, 14, and 15 are given.

Source record↗
NASA NTRS2008

The Lunar Potential Determination Using Apollo-Era Data and Modern Measurements and Models

Since the Apollo era the electric potential of the Moon has been a subject of interest and debate. Deployed by three Apollo missions, Apollo 12, Apollo 14 and Apollo 15, the Suprathermal Ion Detector Experiment (SIDE) determined the sunlit lunar surface potential to be about +10 Volts using the energy spectra of lunar ionospheric thermal ions accelerated toward the Moon. More recently, the Lunar Prospector (LP) Electron Reflectometer used electron distributions to infer negative lunar surface potentials, primarily in shadow. We will present initial results from a study to combine lunar surface potential measurements from both SIDE and the LP/Electron Reflectometer to calibrate an advanced model of lunar surface charging which includes effects from the plasma environment, photoemission, secondaries ejected by ion impact onto the lunar surface, and the lunar wake created downstream by the solar wind-lunar interaction.

Collier, Michael R.↗
NASA NTRS1977

Ionosphere and atmosphere of the moon in the geomagnetic tail

The paper presents calculations of the densities and energies of the various constituents of the lunar ionosphere during the time that the moon is in the geomagnetic tail; the surface concentrations of neon and argon are calculated from a theoretical model to be 3,900 and 1,700, respectively. It is found that a hydrostatic model of the ionospheric plasma is inadequate because the gravitational potential energy of the plasma is considerably smaller than its thermal energy. A hydrodynamic model, comparable to that used to describe the solar wind, is developed to obtain plasma densities and flow velocities as functions of altitude. The electromagnetic properties of the quiescent ionosphere are then investigated, and it is concluded that plasma effects on lunar induction can be neglected for quiescent conditions in the geomagnetic tail lobes.

Daily, W. D.↗
NASA NTRS1976

Solar wind and extreme ultraviolet modulation of the lunar ionosphere/exosphere

The ALSEP/SIDE detectors routinely monitor the dayside lunar ionosphere. Variations in the ionosphere are found to correlate with both the 2800 MHz radio index which can be related to solar EUV and with the solar wind proton flux. For the solar wind, the ionospheric variation is proportionately greater than that of the solar wind. This suggests an amplification effect on the lunar atmosphere due perhaps to sputtering of the surface or, less probably, an inordinate enhancement of noble gases in the solar wind. The surface neutral number density is calculated under the assumption of neon gas. During a quiet solar wind this number agrees with or is slightly above that expected for neon accreted from the solar wind. During an enhanced solar wind the neutral number density is much higher.

Freeman, J. W.↗
NASA NTRS2009

Lunar Surface Potential Increases during Terrestrial Bow Shock Traversals

Since the Apollo era the electric potential of the Moon has been a subject of interest and debate. Deployed by three Apollo missions, Apollo 12, Apollo 14 and Apollo 15, the Suprathermal Ion Detector Experiment (SIDE) determined the sunlit lunar surface potential to be about +10 Volts using the energy spectra of lunar ionospheric thermal ions accelerated toward the Moon. We present an analysis of Apollo 14 SIDE "resonance" events that indicate the lunar surface potential increases when the Moon traverses the dawn bow shock. By analyzing Wind spacecraft crossings of the terrestrial bow shock at approximately this location and employing current balancing models of the lunar surface, we suggest causes for the increasing potential. Determining the origin of this phenomenon will improve our ability to predict the lunar surface potential in support of human exploration as well as provide models for the behavior of other airless bodies when they traverse similar features such as interplanetary shocks, both of which are goals of the NASA Lunar Science Institute's Dynamic Response of the Environment At the Moon (DREAM) team.

Collier, Michael R.↗
NASA NTRS2010

Observing Solar Radio Bursts from the Lunar Surface

Locating low frequency radio observatories on the lunar surface has a number of advantages. Here, we describe the Radio Observatory for Lunar Sortie Science (ROLSS), a concept for a low frequency, radio imaging interferometric array designed to study particle acceleration in the corona and inner heliosphere. ROLSS would be deployed during an early lunar sortie or by a robotic rover as part of an unmanned landing. The prime science mission is to image type II and type III solar radio bursts with the aim of determining the sites at and mechanisms by which the radiating particles are accelerated. Secondary science goals include constraining the density of the lunar ionosphere by searching for a low radio frequency cutoff of the solar radio emissions and constraining the low energy electron population in astrophysical sources. Furthermore, ROLSS serves a pathfinder function for larger lunar radio arrays. Key design requirements on ROLES include the operational frequency and angular resolution. The electron densities in the solar corona and inner heliosphere are such that the relevant emission occurs below 10 MHz, essentially unobservable from Earth's surface due to the terrestrial ionospheric cutoff. Resolving the potential sites of particle acceleration requires an instrument with an angular resolution of at least 2 deg, equivalent to a linear array size of approximately 500 meters. Operations would consist of data acquisition during the lunar day, with regular data downlinks. The major components of the ROLSS array are 3 antenna arms arranged in a Y shape, with a central electronics package (CEP). Each antenna arm is a linear strip of polyimide film (e.g., Kapton (TM)) on which 16 single polarization dipole antennas are located by depositing a conductor (e.g., silver). The arms also contain transmission lines for carrying the radio signals from the science antennas to the CEP.

MacDowall, R. J.↗