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At least 1,153 records · Page 64
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Analysis of a Jupiter swingby out-of-the-ecliptic mission

In addition to the outer planets, much interest is directed toward understanding the solar environment in which those planets and the earth have evolved. One means of obtaining some of the needed data is an out-of-the-ecliptic mission. Direct launch out of earth orbit does not allow acceptable solar latitudes to be achieved with existing launch vehicles. This paper presents the results of a study on using a Jupiter swingby to increase significantly the achievable solar latitudes. Latitudes above 60 deg can be achieved with an Atlas/Centaur/TE364-4 and a Pioneer-class spacecraft reduced in weight by about 50 kg. Jovian center-targeting contours have been generated, and a maximum achievable latitude has been determined as a function of launch year and spacecraft mass. Nominal trajectories are selected, and time histories of significant parameters are presented.

Manning, L. A.↗
NASA NTRS1975

Detection of carbon monoxide in Jupiter

New, ground-based, 5-micron spectra of Jupiter have revealed the presence of a trace quantity of carbon monoxide in the lower atmosphere of the planet. A preliminary analysis suggests a number mixing ratio in the neighborhood of 10 to the minus ninth power and a column abundance of roughly 5 times 10 to the 17th power molecules per sq cm to a depth of at least 2 atmospheres. It is suggested that the observation might be confirmed by microwave techniques.

Beer, R.↗
NASA NTRS1975

Phosphine on Jupiter and implications for the Great Red Spot

A study of the chemistry and photochemistry of the recently discovered phosphine in the atmosphere of Jupiter suggests that the red colorations on this planet result from photochemical production of red phosphorus particles. Chemical-dynamical models of this red phosphorus haze imply that the intensity of the red coloration is a strong function of the strength of vertical turbulent mixing in the atmosphere. If the Jovian Great Red Spot is a region of considerable dynamical activity our model provides a self-consistent explanation for the redness of this region in comparison to the rest of the planet.

Prinn, R. G.↗
NASA NTRS1975

Results of long-term synoptic monitoring of Jupiter's decametric radiation

Results of the analysis of the large, homogeneous set of measurements of Jupiter's emission at 16.7 and 22.2 MHz for the apparitions during the period 1966-1974 were presented. An update of the radio rotation period determination which includes provision for beaming effects due to variations in the Jovicentric declination of the earth was presented. Some estimates of the magnitude of possible long-term variations in the rotation period were also discussed. The data clearly shows the Io-independent emission features associated with the System III central meridian longitudes of all three major Io-related source regions. There is also some evidence for heretofore unrecognized Io-related emission features which are apparently independent of the central meridian longitude. The possibility of three kinds of emission are suggested: (1) Io-stimulated, sharply beamed emission, (2) Io-independent, sharply beamed emission, and (3) Io-stimulated, broadly beamed emission.

Alexander, J. K.↗
NASA NTRS1975

A new methodology to integrate planetary quarantine requirements into mission planning, with application to a Jupiter orbiter

A new methodology is proposed for integrating planetary quarantine objectives into space exploration planning. This methodology is designed to remedy the major weaknesses inherent in the current formulation of planetary quarantine requirements. Application of the methodology is illustrated by a tutorial analysis of a proposed Jupiter Orbiter mission. The proposed methodology reformulates planetary quarantine planning as a sequential decision problem. Rather than concentrating on a nominal plan, all decision alternatives and possible consequences are laid out in a decision tree. Probabilities and values are associated with the outcomes, including the outcome of contamination. The process of allocating probabilities, which could not be made perfectly unambiguous and systematic, is replaced by decomposition and optimization techniques based on principles of dynamic programming. Thus, the new methodology provides logical integration of all available information and allows selection of the best strategy consistent with quarantine and other space exploration goals.

Howard, R. A.↗
NASA NTRS1975

Jupiter: Its infrared spectrum from 10 to 40 microns

Spectral measurements of the thermal radiation from Jupiter in the 16-40 micrometer band were analyzed under the assumption that pressure broadened H2 transitions are responsible for the bulk of the infrared opacity over most of this spectral interval. Both the vertical pressure-temperature profile and the hydrogen mixing ratio were determined. The derived value of the molecular hydrogen mixing ratio, 0.89 + or - 0.11, is consistent with the solar value, 0.86.

Houck, J. R.↗
NASA NTRS1976

Review of investigations performed in the USSR on close approaches of comets to Jupiter and the evolution of cometary orbits

Methods are reviewed for calculating the evolution of cometary orbits with emphasis on the orbital changes that take place when comets pass within the spheres of action of giant planets. Topics discussed include: differences and difficulties in methods used for the calculation of large perturbations by Jupiter; the construction of numerical theories of motion covering the whole period of observations of each comet, allowing for planetary perturbations and the effects of nongravitational forces; and investigations of the evolution of cometary orbits over the 400 year interval 1660-2060. The classical theory of cometary capture is briefly discussed.

Kazimirchak-Polonskaya, E. I.↗
NASA NTRS1976

Relativistic electrons and whistlers in Jupiter's magnetosphere

The path-integrated gain of parallel propagating whistlers driven unstable by an anisotropic distribution of relativistic electrons in the stable trapping region of Jupiter's inner magnetosphere was computed. The requirement that a gain of 3 e-foldings of power balance the power lost by imperfect reflection along the flux tube sets a stably-trapped flux of electrons which is close to the non-relativistic result. Comparison with measurements shows that observed fluxes are near the stably-trapped limit, which suggests that whistler wave intensities may be high enough to cause significant diffusion of electrons accounting for the observed reduction of phase space densities. A crude estimate of the wave intensity necessary to diffuse electrons on a radial diffusion time scale yields a lower limit for the magnetic field fluctuation intensity.

Barbosa, D. D.↗
NASA NTRS1976

Measurements of Jupiter's long-lived features and currents

Recent longitudinal measurements of Jupiter's Red Spot are presented to illustrate the constancy of the 90-day oscillation. Observational parameters of the Red Spot, the three south temperate ovals, and a summary of the zenographic latitudes of the belts are tabulated for the time interval from 1972 to 1975. Drift rates and the mean latitudes of the atmospheric currents for the 1974-75 apparition are presented.

Reese, E. J.↗
NASA NTRS1975

Recirculation of energetic particles in Jupiter's magnetosphere

A significant new finding from analysis of Pioneer 11 observations in the magnetosphere of Jupiter is that there is net streaming of both electrons E above 40 keV and E above 560 keV and protons in the range from .61 to 3.41 MeV away from the planet along high-latitude field lines. This result is compatible with the recent suggestion of Nishida that energetic particles undergo trans-L shell diffusion at low altitudes without significant change of energy. This provides a plausible explanation for the remarkable pitch angle distributions near the equator in the range of L values from 12 to 25; the presence of particles of about 1 MeV energy at the outer edge of the magnetosphere; and hence, via conventional inward diffusion processes, the presence of those having magnetic moments of several hundred MeV per gauss in the inner magnetosphere. The recirculation of energetic particles emerges as an important dynamical feature of the Jovian magnetosphere.-

Sentman, D. D.↗
NASA NTRS1975

The powered swingby and its application to Jupiter orbit mission design

This paper is a description of recent studies of constrained optimal transfer between given hyperbolic asymptotes with an emphasis on the practical aspects of the concept for powered Galilean satellite swingby Jupiter orbit insertion. The effects of orbital inclination on performance gain are discussed and the targeting problem for establishing the optimal swingby is solved. Comparisons of some candidate mission profiles are presented and the advantages and disadvantages of the powered swingby orbit insertion are discussed in the context of recent interactions with the scientific community on the relative merits of several mission profiles now under consideration.

Uphoff, C.↗
NASA NTRS1975

The navigation of a satellite re-encounter in a Jupiter Orbiter mission

Very often in the course of the Jupiter Orbiter-Satellite Tour mission it is desired to have the spacecraft re-encounter a satellite after one complete Jovicentric orbit whose period is resonant with that of the satellite for the purposes of orbit 'cranking' or 'pumping'. This paper develops the deterministic guidance strategy necessary for the implementation of such re-encounters (360 deg transfers). Both single impulse and fuel optimal multiple impulse guidance strategies are developed on the basis of which an estimate of the total navigational fuel cost for the mission is made.

Sherman, G. N.↗
NASA NTRS1975

Preliminary Mariner Jupiter-Saturn 1977 launch/encounter strategy

An overview of mission strategy is presented for Mariner Jupiter-Saturn 1977. A launch/encounter strategy is required which will ensure high value science return for all possible launch combinations. The paper consists of three major sections. Section one is concerned with a statement of mission definition, engineering constraints, and scientific objectives. Section two is concerned with the definition of constraint regions within the MJS77 available trajectory space. The last section derives an example launch/encounter strategy which satisfies a set of engineering and science groundrules.

Wallace, R. A.↗
NASA NTRS1975

Jupiter orbiter lifetime - The hazard of Galilean satellite collision

An assessment of the long-term collision risk is made for an uncontrolled orbiting spacecraft that repeatedly enters the spatial region occupied by the satellites. Numerical data are obtained for 50-year orbit propagations which account approximately for the major perturbative effects of Jupiter oblateness, solar gravity and satellite gravity. A broad statistical viewpoint regarding the question of collision likelihood is adopted and is based on a total sample size of 480 initial orbits distributed among 4 orbit classes, 8 inclinations and 15 initial epochs. Numerical results compare favorably with an analytical prediction formula which shows that eccentric, low-inclination orbits have high collision probability.

Friedlander, A. L.↗