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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Small planetary missions for the Space Shuttle

The paper deals with the concept of a small planetary mission that might be described as one which: (1) focuses on a narrow set of discovery-oriented objectives, (2) utilizes largely existing and proven subsystem capabilities, (3) does not tax future launch vehicle capabilities, and (4) is flexible in terms of mission timing such that it can be easily integrated with launch vehicle schedules. Three small planetary mission concepts are presented: a tour of earth-sun Lagrange regions in search of asteroids which might be gravitationally trapped, a network of spacecraft to search beyond Pluto for a tenth planet; and a probe which could be targeted for infrequent long period 'comets of opportunity' or for a multitude of shorter period comets.

Staehle, R. L.↗
NASA NTRS1980

Planetary magnetism

Planetary spacecraft have now probed the magnetic fields of all the terrestrial planets, the moon, Jupiter, and Saturn. These measurements reveal that dynamos are active in at least four of the planets, Mercury, the earth, Jupiter, and Saturn but that Venus and Mars appear to have at most only very weak planetary magnetic fields. The moon may have once possessed an internal dynamo, for the surface rocks are magnetized. The large satellites of the outer solar system are candidates for dynamo action in addition to the large planets themselves. Of these satellites the one most likely to generate its own internal magnetic field is Io.

Russell, C. T.↗
NASA NTRS1980

The role of Ekman flow and planetary waves in the oceanic cross-equatorial heat transport

A numerical model is used to mechanistically simulate the oceans' seasonal cross-equatorial heat transport. The basic process of Ekman pumping and drift is able to account for a large amount of the cross-equatorial flux. Increased easterly wind stress in the winter hemisphere causes Ekman surface drift poleward, while decreased easterly stress allows a reduction in the poleward drift in the summer hemisphere. The addition of planetary and gravity waves to this model does not alter the net cross-equatorial flow, although the planetary waves are clearly seen. On comparison with Oort and Vonder Haar (1976), this adiabatic advective redistribution of heat is seen to be plausible up to 10-20 deg N, beyond which other dynamics and thermodynamics are indicated.

Schopf, P. S.↗
NASA NTRS1981

Fourier spectroscopy on planetary missions including Voyager

In the last dozen years spaceborne Fourier transform spectrometers have obtained infrared emission spectra of Earth, Mars, Jupiter, Saturn and Titan as well as of the Galilean and other Saturnian satellites and Saturn's rings. Intercomparisons of the properties of planetary atmospheres and of the characteristics of solid surfaces are now feasible. The principles of remotely sensing the environment on a planetary body are dicussed. Special consideration is given to the most recent results obtained by the Voyager infrared investigation on the Saturn system.

Hanel, R. A.↗
NASA NTRS1981

Significant achievements in the planetary geology program, 1981

Recent developments in planetology research as reported at the 1981 NASA Planetary Geology Principal Investigators meeting are summarized. The evolution of the solar system, comparative planetology, and geologic processes active on other planets are considered. Galilean satellites and small bodies, Venus, geochemistry and regoliths, volcanic and aeolian processes and landforms, fluvial and periglacial processes, and planetary impact cratering, remote sensing, and cartography are discussed.

Holt, H. E.↗
NASA NTRS1980

Cost reduction in space operations - Structuring a planetary program to minimize the annual funding requirement as opposed to minimizing the program runout cost

An approach is proposed for the structuring of a planetary mission set wherein the peak annual funding is minimized to meet the annual budget restraint. One aspect of the approach is to have a transportation capability that can launch a mission in any planetary opportunity; such capability can be provided by solar electric propulsion. Another cost reduction technique is to structure a mission test in a time sequenced fashion that could utilize essentially the same spacecraft for the implementation of several missions. A third technique would be to fulfill a scientific objective in several sequential missions rather than attempt to accomplish all of the objectives with one mission. The application of the approach is illustrated by an example involving the Solar Orbiter Dual Probe mission.

Herman, D. H.↗
NASA NTRS1980

On the detection of other planetary systems - Detection of intrinsic thermal radiation

There is currently no unambiguous observational evidence for the existence of other planetary systems. One possible way to detect and study such systems is infrared observations of continuum blackbody radiation from planets revolving around other stars. It is shown that the effective temperature of large planets revolving around mid- to late-spectral-type main-sequences stars is set by energy sources internal to the planet rather than by equilibrium with the radiation field of the central star, making them easier to detect than had been previously thought. Consideration is given to the two major observational constraints on detecting planetary companions to nearby stars, namely, angular resolution and sensitivity. A comparison is made between the performance of an ambient (T 200 K), single-aperture telescope and a cooled interferometer. In each case the required aperture (baseline) is large (in the 10-m class), but consistent with Shuttle launch capability.

Black, D. C.↗
NASA NTRS1981

Planetary radio astronomy observations from Voyager 1 near Saturn

The Voyager 1 planetary radio astronomy experiment detected two distinct kinds of radio emissions from Saturn. The first, Saturn kilometric radiation, is strongly polarized, bursty, tightly correlated with Saturn's rotation, and exhibits complex dynamic spectral features somewhat reminiscent of those in Jupiter's radio emission. It appears in radio frequencies below about 1.2 megahertz. The second kind of radio emission, Saturn electrostatic discharge, is unpolarized, extremely impulsive, loosely correlated with Saturn's rotation, and very broadband, appearing throughout the observing range of the experiment (20.4 kilohertz to 40.2 megahertz). Its sources appear to lie in the planetary rings.

Warwick, J. W.↗
NASA NTRS1981

Negative ions in the ionospheres of planetary bodies without atmospheres

It is noted that negative ions may be formed in the ionospheres of Mercury, the moon, and Jupiter's satellites with densities of a few percent of the ionospheric electron density. Negative ions result from three mechanisms at the planetary surface: charge inversion during energetic proton scattering, with simultaneous secondary negative ion emission, and micrometeorite impacts. The density and distribution of negative ions around planetary bodies depends primarily on the negative ion lifetimes determined through photodetachment by solar radiation.

Wekhof, A.↗
NASA NTRS1981

Investigation of some of the principal geometric effects on planetary polarization

The paper investigates geometric effects which may influence the interpretation of observed polarimetric data of planets used to deduce physical properties of aerosols and their distributions in planetary atmospheres. The effects studied include the observer's distance to the planet, horizontal inhomogeneity of the planetary atmosphere, and deviation from a spherical body. The results will facilitate the present and future analyses of spacecraft data.

Kawabata, K.↗
NASA NTRS1981

A far-infrared emission feature in carbon-rich stars and planetary nebulae

The 16-30 micron spectra of several carbon stars and the planetary nebulae IC 418 and NGC 6572 have been obtained using the NASA C-141 Kuiper Airborne Observatory. A newly observed emission feature appears in the spectrum of IRC +10216 and several other carbon stars at wavelengths greater than 24 microns. The feature is interpreted as resulting from a solid-state resonance in the dust grains which have condensed around these stars. A similar feature appears in the spectra of IC 418 and NGC 6572, implying that the same type of dust is present. Since the dust probably condensed from a carbon-rich gas, this indicates an evolutionary link between carbon stars and these planetary nebulae. No identification for the grain material has been found, but some clues are apparent which could aid in the identification.

Forrest, W. J.↗
NASA NTRS1981

Recent progress in exobiology and planetary biology

Recent work in the fields of exobiology, the study of the possible characteristics of extraterrestrial life, and planetary biology, the study of life forms as a function of planetary conditions, is reviewed. Searches conducted for life on Mars by the Viking Landers and on Titan by Voyager 1 are considered, and the origin of life on earth is considered in relation to the question of the inorganic trace elements in living systems that are required for life. The question of the origin of terrestrial life from spores carried through the interstellar medium is examined, and the unlikelihood of the survival of such spores except within meteorites or dust particles is pointed out. Studies of organic molecules present in the interstellar medium are indicated as evidence that the conditions necessary for the formation of life can exist in various locations throughout the universe. Investigations of the molecular evolution of life on earth and of life under extreme conditions of heat, cold, drought and ultraviolet radiation, and of the organic compounds found in meteorites and comets are also discussed. The importance of a mechanism of heredity, such as terrestrial DNA, to the evolution of terrestrial and possible extraterrestrial life is pointed out.

Jukes, T. H.↗
NASA NTRS1980

A model for nitrogen isotopic variations in the lunar regolith - Possible solar system contributions from a nearby planetary nebula

To account for the observed secular increase of the N-15/N-14 ratio in lunar samples, a model is developed which envisions an encounter between a planetary nebula and the solar system during the first few hundred million years of its history. The principal effects of the encounter for the sun's outer convective zone, and hence solar wind, due to accretion of planetary nebula material with its distinct nucleosynthetic history are delineated. Associated material contributions to planets and meteorite parent bodies are considered and contraints relevant to this possibility are discussed.

Ray, J.↗
NASA NTRS1981

Infrared experiments for spaceborne planetary atmospheres research. Full report

The role of infrared sensing in atmospheric science is discussed and existing infrared measurement techniques are reviewed. Proposed techniques for measuring planetary atmospheres are criticized and recommended instrument developments for spaceborne investigations are summarized for the following phenomena: global and local radiative budget; radiative flux profiles; winds; temperature; pressure; transient and marginal atmospheres; planetary rotation and global atmospheric activity; abundances of stable constituents; vertical, lateral, and temporal distribution of abundances; composition of clouds and aerosols; radiative properties of clouds and aerosols; cloud microstructure; cloud macrostructure; and non-LTE phenomena.

Source record↗
NASA NTRS1981

Voyager 1 assessment of Jupiter's planetary magnetic field

An estimate of Jupiter's planetary magnetic field is obtained from the Voyager 1 observations of the Jovian magnetosphere. An explicit model for the magnetodisc current system is combined with a spherical harmonic model of the planetary field with both sets of parameters determined simultaneously using a nonlinear generalized inverse methodology. The resulting model fits the observations extremely well throughout the analysis interval (r 20 Jovian radii). The Jovian internal field model obtained from the Voyager 1 data is very similar to the octopole Pioneer 11 models. The best fitting magnetodisc lies in the centrifugal equator, 2/3 of the way between the rotational and magnetic equators, as appropriate for centrifugal loading of the magnetosphere by a cold plasma.

Connerney, J. E. P.↗
NASA NTRS1982

Vibrational-Rotational Spectroscopy For Planetary Atmospheres, volume 1

Comprehensive information on the composition and dynamics of the varied planetary atmospheres is summarized. New observations resulted in new demands for supporting laboratory studies. Spectra observed from spacecraft used to interpret planetary atmospheric structure measurements, to aid in greenhouse and cloud physics calculations, and to plan future experiments are discussed. Current findings and new ideas of physicists, chemists, and planetry astronomers relating to the knowledge of the structure of things large and small, of planets and of molecules are summarized.

Mumma, M. J.↗
NASA NTRS1982

Stratification effects and IUE spectra of high excitation planetaries

Individual strips across IUE low resolution images of a number of high excitation planetaries with appreciable angular disks (including NGC 2452, 3242, 6818, and IC 1297) are analyzed to assess stratification effects. The familiar enhancement of high excitation lines toward the center is well exhibited, but some unexpected structural features are found in NGC 2452 where C IV shows a single central maximum, but C III, Ne IV, and He II seem to have a central dip. The new IUE data permit improved chemical composition estimates for several planetaries previously analyzed by Aller and Czyzak.

Feibelman, W.↗
NASA NTRS1982

Activities in planetary geology for the physical and earth sciences

A users guide for teaching activities in planetary geology, and for physical and earth sciences is presented. The following topics are discussed: cratering; aeolian processes; planetary atmospheres, in particular the Coriolis Effect and storm systems; photogeologic mapping of other planets, Moon provinces and stratigraphy, planets in stereo, land form mapping of Moon, Mercury and Mars, and geologic features of Mars.

Dalli, R.↗