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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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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Quasi-axisymmetric circulation and superrotation in planetary atmospheres

Atmospheric superrotation is ubiquitous in the solar system, and numerous theoretical models have been proposed to describe the effect. However, no model is fully accepted. Problems are primarily related to an understanding of the angular momentum and the energy budgets. In connection with the present investigation, attention is given to hybrid models, where three-dimensional models may describe eddy processes and two-dimensional symmetric models may describe the global scale circulation in the framework of a viscous medium. It is believed that the concept of an axisymmetric circulation is still useful. It is the main purpose of the current investigation to explore some of the properties of the circulation in planetary atmospheres. It is assumed that the eddy transports are downgradient or diffusive in nature. Energy and momentum are perceived to cascade from the global scale circulation driven by the sun to the smaller scale eddies which in turn determine the diffusive properties. A numerical model of the Venusian circulation is presented, and results are discussed for different conditions of static stability.

Mayr, H. G.↗
NASA NTRS2020

TPSAS-NF1676L-35628-DND

CHARISMA responds to the Committee on Astrobiology and Planetary Science (CAPS)'s recommendation to study a large/medium-class dedicated space telescope for planetary science. We are nearing the end of the Hubble Space Telescope lifetime, at which point the continuity of solar system UV measurements will be lost. Scientific objectives critically dependent on UV capabilities include studies of exospheric and auroral emissions in planetary atmospheres and plumes. CHARISMA will also revolutionize our understanding of time-dependent phenomena in our solar system currently not supported by programs intended to observe and visit new targets. The time-domain phenomena to be explored by CHARISMA include interaction of planetary magnetospheres with the solar wind, Venus and giant planet atmospheric dynamics, icy satellite geologic activity and surface evolution, cometary evolution, and evolving ring phenomena. CHARISMA also enables a comprehensive survey of the spectral characterization of minor bodies across the solar system, which requires a large time allocation not supported by existing facilities. CHARISMA will examine the benefits of advanced in-Space Assembly (iSA) technologies that enable a 10-m class aperture at New-Frontiers cost. CHARISMA will have the greatest impacts on science objectives particularly sensitive to dynamically evolving phenomena.

C L Young↗
NASA NTRS1983

Atmospheric tides on Venus. III - The planetary boundary layer

Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.

Dobrovolskis, A. R.↗
NASA NTRSDate not supplied

Imaging Science Requirements for a Uranus Flagship Mission

Introduction: Our presentation will summarize the requirements for UV/Visible/Near-IR remote-sensing imaging science instruments (including mapping spectrometers) envisioned for the Uranus Orbiter and Probe (UOP) mission recommended by the recent planetary decadal survey. The Uranus system offers many targets for imaging investigations. Imaging science investigations are crucial to answering fundamental questions about various physical processes that shape the Uranian system and drive its evolution. Each science objective addressed through imaging has requirements for observation and illumination geometries as well as coverage and resolution in the spatial, spectral and temporal dimensions. By combining the requirements for the diverse science targets in the Uranian system, we present a set of overarching imaging science requirements for UOP. Atmospheric Science: The study of Uranus’ atmosphere is crucial in understanding the planet's energy balance and interior heat flux. Imaging observations map how the atmosphere scatters incident solar radiation. Imaging is key to characterizing planetary-scale energy/material transport though global atmospheric dynamics and local meteorology. Hyperspectral mapping combined with radiative transfer analysis reveals the vertical distribution of clouds and hazes. Chronicling temporal variabilities of atmospheric features is key to understanding the various processes that operate within the dynamic Uranian atmosphere. A comprehensive understanding of Uranus' atmosphere is essential in deciphering the planet's origins and evolution as well as providing insight into the broader field of planetary and exoplanetary science. Magnetospheric Interactions: Imaging science is critical to understand the elusive Uranian aurorae. Mapping the aurorae and their temporal dynamics will reveal the interaction of Uranus’ complex magnetosphere with the solar wind. The apparent decades-long cooling of Uranus’ upper atmosphere is thought to be due to changes in energy input from the overlying magnetosphere, and so mapping and quantifying the auroral evidence for this energy flux is particularly relevant for upper atmospheric science In addition, Uranus’ large moons may generate auroral footprints, which can be used to constrain the planet’s unusual magnetic field structure. Satellite Interiors: Imaging science can address the potential habitability of the larger moons of Uranus by measuring their shapes and rotational states (including librations), which combined with gravity data are crucial to understanding their internal density structure. Satellite Origins: Origin markers such as organics and volatiles may be preserved on the satellite surfaces, which may be sensed by UV/IR mapping. Imaging combined with the moons’ densities may reveal whether the moons formed in Uranus’ circumplanetary disk, rings, or from ejecta of a giant impact on Uranus. Satellite Geology: Imaging investigations, including stereo imaging to obtain topography, will enable constraining each satellite’s geologic history by investigating the distributions and morphologies of impact craters, tectonic and potential cryovolcanic features, and regolith and mass wasting deposits. These records will help unravel the past complex history of orbital resonances that occurred between Uranian satellites, which may have driven geologic activity. Analyses of these features will also point to resurfacing styles and modification processes important for understanding each moon’s thermal evolution, and any present-day geological activity, including potential subsurface deep oceans or possible current activity. Additionally, hyperspectral imaging will enable mapping the surface composition and identifying the potential presence of material that may point to a subsurface ocean, such as ammonia-bearing species. Rings and Small Moons: Imaging observations elucidate the physical processes that contribute to the complex ring-moon system’s inferred unstable state. Imaging surveys will seek smaller moons and other debris that could provide evidence of past collisions, while precise astrometric data of moons will determine the current dynamical state of the system. Many of Uranus' rings are exceptionally narrow, and images of the rings covering a broad range of longitudes, and high-resolution images of features within the rings will reveal how these rings are confined and maintained, as well as illustrating the rings' internal structure and dynamics. Images of the rings and moons obtained at a variety of wavelengths and lighting conditions are also needed to quantify the composition and the size distribution of the small satellites and ring particles.

K M Sayanagi↗
NASA NTRS1980

Planetary wave coupling between the troposphere and the middle atmosphere as a possible sun-weather mechanism

The possibility of planetary wave coupling between the troposphere and solar-induced alterations in the upper atmosphere providing a viable mechanism for giving rise to sun-weather relationships is investigated. Some of the observational evidence for solar-activity-induced effects on levels of the upper atmosphere ranging from the thermosphere down to the lower stratosphere are reviewed. It is concluded that there is evidence for such effects extending down to the middle stratosphere and below. Evidence is also reviewed that these effects are due to changes in solar ultraviolet emission during disturbed solar conditions. A theoretical planetary wave model is then used to see at what levels in the upper atmosphere moderate changes in the mean zonal wind state would result in tropospheric changes. It is concluded that changes in the mean zonal flow of about 20% at levels in the vicinity of 35 km or below would give rise to changes in the tropospheric planetary wave pattern that are less than but on the same order as the observed interannual variability in the tropospheric wave pattern at middle and high latitudes.

Geller, M. A.↗
NASA NTRS1972

Definition phase of Grand Tour missions/radio science investigations study for outer planets missions

Scientific instrumentation for satellite communication and radio tracking systems in the outer planet exploration mission is discussed. Mission planning considers observations of planetary and satellite-masses, -atmospheres, -magnetic fields, -surfaces, -gravitational fields, solar wind composition, planetary radio emissions, and tests of general relativity in time delay and ray bending experiments.

Tyler, G. L.↗
NASA NTRS1989

Interpretation of surface and planetary directional albedos for vegetated regions

An atmospheric solar radiation model has been coupled with surface reflectance measurements for two vegetation types, pasture land and savannah, in order to address several issues associated with understanding the directional planetary albedo; i.e., the dependence of planetary albedo upon solar zenith angle. These include an elucidation of processes that influence the variation of planetary albedo with solar zenith angle, as well as emphasizing potential problems associated with converting narrowband planetary albedo measurements to broadband quantities. It is suggested that, for vegetated surfaces, this latter task could be somewhat formidable, since the model simulations indicate that narrowband to broadband conversions strongly depend upon vegetation type. A further aspect of this paper is to illustrate a procedure by which reciprocity inconsistencies within a bidirectional reflectance dataset, if they are not too severe, can be circumvented.

Cess, Robert D.↗
NASA NTRS2024

Solar System Science With the Single Aperture Large Telescope for Universe Studies Space Observatory

Single Aperture Large Telescope for Universe Studies (SALTUS) is a NASA Astrophysics Probe Explorer (APEX)-class mission concept employing a robust far-infrared pointed space observatory. SALTUS comprises a 14-m inflatable reflector that provides 16× the sensitivity and 4× the angular resolution of Herschel, with a sunshield that radiatively cools the primary to 45 K, along with cryogenic detectors that collectively span the 34 to 660 μm far-infrared spectral range at high and moderate spectral resolutions. The high sensitivity and high spectral resolving power of the SALTUS heterodyne receivers enable both submillimeter and far-infrared observations of trace compounds comprising water and its isotopologues, hydrogen deuteride (HD), and a plethora of molecular species containing carbon, hydrogen, nitrogen, oxygen, phosphorus, or sulfur (CHNOPS), all of which are obscured by the Earth’s atmosphere. The high sensitivity and broadband spectral coverage of the SALTUS far-infrared grating spectrometer enables far-infrared observations of the lattice vibrational spectral signatures of ices and mineral grains contained within a wide variety of solar system targets, including comets, planetary atmospheres, near Enceladus’ plumes, and on the surfaces of icy moons, Jupiter trojans, centaurs, and Kuiper Belt objects. A key objective of SALTUS is to measure HDO∕H 2 O in both Jupiter family and Oort cloud comets. Additional observations will allow us to characterize the water torus around Saturn generated by its icy moon Enceladus, determine the source of stratospheric water in the giant planets, ascertain the time evolution of water on Venus, and search for H 2 O plumes on Europa, Ganymede, and Callisto. SALTUS will measure HD∕H 2 in all four giant planets to constrain models of their origin. SALTUS can also measure the abundance of CHNOPS-containing molecules and halides in the atmosphere of Venus and in the comae of comets. We review the extensive amount of solar system science achievable with SALTUS for both the Guaranteed Time Observation and the Guest Observer APEX mission observing programs.

Carrie M. Anderson↗
NASA NTRS1999

Mercury's Magnetosphere

Among the major discoveries made by the Mariner 10 mission to the inner planets was the existence of an intrinsic magnetic field at Mercury with a dipole moment of approx. 300 nT R(sup 3, sub M). This magnetic field is sufficient to stand off the solar wind at an altitude of about 1 R(sub M) (i.e. approx. 2439 km). Hence, Mercury possesses a 'magnetosphere' from which the so]ar wind plasma is largely excluded and within which the motion of charged particles is controlled by the planetary magnetic field. Despite its small size relative to the magnetospheres of the other planets, a Mercury orbiter mission is a high priority for the space physics community. The primary reason for this great interest is that Mercury unlike all the other planets visited thus far, lacks a significant atmosphere; only a vestigial exosphere is present. This results in a unique situation where the magnetosphere interacts directly with the outer layer of the planetary crust (i.e. the regolith). At all of the other planets the topmost regions of their atmospheres become ionized by solar radiation to form ionospheres. These planetary ionospheres then couple to electrodynamically to their magnetospheres or, in the case of the weakly magnetized Venus and Mars, directly to the solar wind. This magnetosphere-ionosphere coupling is mediated largely through field-aligned currents (FACs) flowing along the magnetic field lines linking the magnetosphere and the high-latitude ionosphere. Mercury is unique in that it is expected that FACS will be very short lived due to the low electrical conductivity of the regolith. Furthermore, at the earth it has been shown that the outflow of neutral atmospheric species to great altitudes is an important source of magnetospheric plasma (following ionization) whose composition may influence subsequent magnetotail dynamics. However, the dominant source of plasma for most of the terrestrial magnetosphere is the 'leakage'of solar wind across the magnetopause and more direct entry through the northern and southern cusps. Although Mariner 10 did not return plasma composition measurements, the Hermean magnetosphere should be ideal for measuring the manner and rate of solar wind plasma entry due to the lack of strong internal atmospheric sources. Finally, the solar wind conditions experienced by Mercury as it orbits the Sun at 0.31 to 0.47 AU are quite different from those typically encountered by the Earth. This may allow for new understanding of the external factors affecting the transfer of mass, momentum and energy from the solar wind to planetary magnetospheres. This article provides a brief overview of what is now known about Mercury's magnetosphere and why it is a priority target for future planetary missions.

Slavin, J. A.↗
NASA NTRS1987

Neutral upper atmospheres of Venus and Mars

Results obtained over the last 21 years from satellite measurements of the neutral upper atmospheres of Venus and Mars are discussed. Particular attention is given to the chemistry of the neutral upper atmospheres of the two planets, the exospheric temperatures, and the sensitivity of their atmospheric temperatures to solar activity. Various theoretical models used to interpret the planetary atmospheric data are discussed.

Keating, G. M.↗
NASA NTRS1991

Planetary astronomy

The authors profile the field of astronomy, identify some of the key scientific questions that can be addressed during the decade of the 1990's, and recommend several facilities that are critically important for answering these questions. Scientific opportunities for the 1990' are discussed. Areas discussed include protoplanetary disks, an inventory of the solar system, primitive material in the solar system, the dynamics of planetary atmospheres, planetary rings and ring dynamics, the composition and structure of the atmospheres of giant planets, the volcanoes of IO, and the mineralogy of the Martian surface. Critical technology developments, proposed projects and facilities, and recommendations for research and facilities are discussed.

Morrison, David↗
NASA NTRS1992

Perspectives from space: NASA classroom information and activities

This booklet contains the information and classroom activities included on the backs of the eight poster series, 'Perspectives From Space'. The first series, Earth, An Integrated System, contains information on global ecology, remote sensing from space, data products, earth modeling, and international environmental treaties. The second series, Patterns Among Planets, contains information on the solar system, planetary processes, impacts and atmospheres, and a classroom activity on Jupiter's satellite system. The third series, Our Place In The Cosmos, contains information on the scale of the universe, origins of the universe, mission to the universe, and three classroom activities. The fourth series, Our Sun, The Nearest Star, contains information on the Sun. The fifth series, Oasis Of Life, contains information on the development of life, chemical and biological evolution on Earth and the search for other life in the universe. The sixth series, The Influence Of Gravity, contains information on Newton's Law of Gravity, space and microgravity, microgravity environment, and classroom activities on gravity. The seventh series, The Spirit Of Exploration, contains information on space exploration, the Apollo Program, future exploration activities, and two classroom activities. The eighth series, Global Cooperation, contains information on rocketry, the space race, and multi-nation exploration projects.

Source record↗
NASA NTRS1993

Dissociative recombination in planetary ionospheres

Ionization in planetary atmospheres can be produced by solar photoionization, photoelectron impact ionization, and, in auroral regions, by impact of precipitating particles. This ionization is lost mainly in dissociative recombination (DR) of molecular ions. Although atomic ions cannot undergo DR, they can be transformed locally through ion-molecule reactions into molecular ions, or they may be transported vertically or horizontally to regions of the atmosphere where such transformations are possible. Because DR reactions tend to be very exothermic, they can be an important source of kinetically or internally excited fragments. In interplanetary thermospheres, the neutral densities decrease exponentially with altitude. Below the homopause (or turbopause), the atmosphere is assumed to be throughly mixed by convection and/or turbulence. Above the homopause, diffusion is the major transport mechanism, and each species is distributed according to its mass, with the logarithmic derivative of the density with repect to altitude given approximately by -1/H, where H = kT/mg is the scale height. In this expression, T is the neutral temperature, g is the local acceleratiion of gravity, and m is the mass of the species. Thus lighter species become relatively more abundant, and heavier species less abundant, as the altitude increases. This variation of the neutral composition can lead to changes in the ion composition; furthermore, as the neutral densities decrease, dissociative recombination becomes more important relative to ion-neutral reactions as a loss mechanism for molecular ions.

Fox, J. L.↗
NASA NTRS2003

Research on Spectroscopy, Opacity, and Atmospheres

For planetary and telluric atmosphere projects the solar irradiance spectrum is required as the input at the top of the atmosphere. It has never been observed. People ask me to compute it. I can compute it theoretically using both known and predicted lines and get agreement averaged over a nanometer but there is no way to predict the resolved spectrum when only half the lines are known. In other stars the situation is worse because the signal-to-noise and resolution of the observations are worse. Logically one has to know a priori what is in the spectrum in order to interpret it; there is not enough information in the observed spectrum itself (qualifiers are given). Basically we need a list of all the energy levels of all atoms and molecules that matter. From that list can be generated all the lines. With the energy levels and line positions known, one can measure gf values, lifetimes, damping, or one can determine a theoretical or semiempirical Hamiltonian whose eigenvalues and eigenvectors produce a good match to the observed data, and that can then be used to generate additional radiative and collisional data for atoms or molecules.

Kurucz, Robert L.↗