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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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NASA NTRS1975

Probing a planetary atmosphere - Pioneer Venus spacecraft description

This paper describes the four Pioneer Venus probe spacecraft which will explore the atmosphere of Venus in mid-December, 1978. The probes, one large and three small, will carry a complement of sixteen scientific instruments which will make measurements from entry (200 km-altitude) down to the planet surface. The surface environment, approximately 770 K temperature and 95 bar. pressure, leads to a design in which the equipment complement is housed in internally insulated, spherical pressure vessels. Entry deceleration and stabilization are provided by 45 deg. half-angle conical forebodies, heat protected by carbon phenolic ablative heat shields. For the large probe, a parachute provides additional retardation between 67 and 44 km altitude, a region of extreme scientific interest.

Nolte, L. J.↗
NASA NTRS1975

Langley Research Center entry aerothermodynamic technology development in support of Pioneer Venus multiprobe mission studies

A program of entry aerothermodynamics has been conducted to support the Pioneer Venus multiprobe mission. Aspects of the study include radiative property data, radiative blockage effectiveness measurements, heating calculations, aerodynamic and convective heating studies, and radio communications blackout models. Some of the historical background for the investigation is reviewed, and recommendations are made concerning the use of the developed technology in probe design and the continuation of certain elements of the program.

Olstad, W. B.↗
NASA NTRS1975

Pioneer Jupiter Orbiter/Probe mission. II - Atmospheric Probe design considerations

Probe design considerations for a 1981 Pioneer Jupiter Orbiter/Probe mission are summarized. Extensive engineering analysis, design, and proof-of-concept testing of a reference probe system developed during the past three years are reviewed. Mission compatibility, science measurements, environmental characteristics, spacecraft interfaces, subsystem constraints, technology development, and programmatic factors are reviewed and discussed. It is demonstrated that for a low-entry-angle, daylight mission to Jupiter a 150 kg semiautonomous entry probe system utilizing state of the art technology is compatible with all the requirements.

Bradley, F. E.↗
NASA NTRS1975

Pioneer 11's encounter with Jupiter and mission to Saturn

Results of Pioneer 11's encounter with Jupiter are reviewed, and present plans for its approach to Saturn are discussed. The spacecraft is described together with its instrumentation, Jupiter-encounter operations, and scientific investigations. Scientific objectives at Saturn are outlined, including imaging of the planet, magnetospheric studies, measurements of Titan's mass and ephemeris, estimates of the mass of Saturn's rings, and penetration of the ring plane, particularly the D ring.

Dyer, J. W.↗
NASA NTRS1975

The Pioneer 10 plasma analyzer results at Jupiter

Results are reported for the Pioneer 10 plasma-analyzer experiment at Jupiter. The analyzer system consisted of dual 90-deg quadrispherical electrostatic analyzers, multiple charged-particle detectors, and attendant electronics; it was capable of determining the incident plasma-distribution parameters over the energy range from 100 to 18,000 eV for protons and from approximately 1 to 500 eV for electrons. Data are presented on the interaction between the solar wind and the Jovian magnetosphere, the interplanetary ion flux, observations of the magnetosheath plasma, and traversals of the bow shock and magnetopause. Values are estimated for the proton isotropic temperature, number density, and bulk velocity within the magnetosheath flow field as well as for the beta parameter, ion number density, and magnetic-energy density of the magnetospheric plasma. It is argued that Jupiter has a reasonably thick magnetosphere somewhat similar to earth's except for the vastly different scale sizes involved.

Wolfe, J. H.↗
NASA NTRS1975

Pioneer 10 - Observations of energetic electrons in the Jovian magnetosphere

Data obtained by Pioneer 10 on the properties of energetic electrons in the Jovian magnetosphere are analyzed. The basic detectors (seven miniature Geiger-Mueller tubes) are described together with the signal processor and sampling techniques. The model of Jupiter used in the data analysis is a centered dipole with a tilt of 9.5 deg toward 230 deg System III longitude. The energetic-electron observations within the inner magnetosphere are found to indicate that radial as well as pitch-angle diffusion of energetic electrons must take place very rapidly. Outbound observations within the magnetodisk (the region beyond 20 Jupiter radii) are found to indicate a spiraling of the apparent location of the longitude of the dipole tilt, while inbound data indicate a constant value for the apparent longitude of the dipole tilt out to 70 Jupiter radii.

Randall, B. A.↗
NASA NTRS1975

Summary of initial results from the GSFC fluxgate magnetometer on Pioneer 11

The main magnetic field of Jupiter was measured by the Fluxgate Magnetometer on Pioneer 11 and analysis reveals it to be relatively more complex than expected. In a centered spherical harmonic representation with a maximum order of n = 3 (designated GSFC model 04), the dipole term (with opposite polarity to the Earth's) has a moment of 4.28 Gauss x (Jupiter radius cubed), tilted by 9.6 deg towards a system 111 longitude of 232. The quadrupole and octupole moments are significant, 24% and 21% of the dipole moment respectively, and this leads to deviations of the planetary magnetic field from a simple offset tilted dipole for distances smaller than three Jupiter radii. The GSFC model shows a north polar field strength of 14 Gauss and a south polar field strength of 10.4 Gauss. Enhanced absorption effects in the radiation belts may be predicted as a result of field distortion.

Acuna, M. H.↗
NASA NTRS1976

Future exploration of Venus (post-Pioneer Venus 1978)

A comprehensive study was performed to determine the major scientific unknowns about the planet Venus to be expected in the post-Pioneer Venus 1978 time frame. Based on those results the desirability of future orbiters, atmospheric entry probes, balloons, and landers as vehicles to address the remaining scientific questions were studied. The recommended mission scenario includes a high resolution surface mapping radar orbiter mission for the 1981 launch opportunity, a multiple-lander mission for 1985 and either an atmospheric entry probe or balloon mission in 1988. All the proposed missions can be performed using proposed space shuttle upper stage boosters. Significant amounts of long-lead time supporting research and technology developments are required to be initiated in the near future to permit the recommended launch dates.

Colin, L.↗
NASA NTRS1974

Science aspects of a 1980 flyby of Comet Encke with a Pioneer spacecraft

Results are presented of an investigation of the feasibility of a 1980 flyby of Comet Encke using a Pioneer class spacecraft. Specific areas studied include: science objectives and rationale; science observables; effects of encounter velocity; science encounter and targeting requirements; selection and description of science instruments; definition of a candidate science payload; engineering characteristics of suggested payload; value of a separable probe; science instruments for a separable probe; science payload integration problems; and science operations profile.

Jaffe, L. D.↗
NASA NTRS1976

Pioneer Venus entry simulator

To assure successful tracking of the four Pioneer Venus probes, it is necessary for the deep space station receiver operators to be familiar with the characteristics of the received signals. As an aid for training the operators for this mission, signal simulators have been developed which completely duplicate the probe signals. This article describes the method used for generating these test signals.

Johns, C. E.↗
NASA NTRS1976

The radial variation of solar flare proton anisotropies observed in deep space on Pioneers 10 and 11

The anisotropy of solar-flare protons (greater than 3 MeV) was evaluated at the time of maximum for each of 24 events measured by Pioneers 10 and 11 and was observed to decrease gradually between 1 and 4.7 AU. Since diffusive streaming is related directly to the effective diffusion coefficient parallel to the interplanetary spiral magnetic field, these observations provide a measure of the radial dependence of interplanetary diffusion parameters. Analysis of these results suggests that the spiral field increases gradually with heliocentric distance. An expression is given for the radial dependence of that field.

Mccarthy, J.↗
NASA NTRS1975

Measurements of cosmic ray anisotropies from Pioneers 10 and 11

A progress report is presented on cosmic ray anisotropy measurements performed in interplanetary space on the Pioneers 10 and 11. A directional Cerenkov counter, sensitive to protons and alpha particles with kinetic energies exceeding 480 MeV/nucleon, was used to determine east-west and north-south anisotropies. Large variations in anisotropies with a time scale of about 60 days were found for the period April-November 1973. The total data set shows an east-west anisotropy of 0.46 plus or minus 0.11% and a north-south anisotropy of 0.03 plus or minus 0.11%. This result for the east-west anisotropy is compatible with a large value of the ratio of the perpendicular to the parallel components of the diffusion coefficient.

Axford, W. I.↗
NASA NTRS1975

The time and spatial behavior of solar flare proton anisotropies observed in deep space on Pioneers 10 and 11

The anisotropy of solar flare protons from the direction of the 'garden hose' magnetic field line has been analyzed for 24 events observed by the University of Chicago experiment on Pioneers 10 and 11 in 1972 and 1973. The anisotropy versus time profiles during individual events are in general consistent with diffusive propagation, but several cases are observed where the decay is better described by an exponential time decay. The anisotropy amplitude evaluated at the time of maximum intensity for each event shows evidence for a gradual decrease with increasing distance from the sun which is qualitatively consistent with diffusive propagation and suggests that the effective interplanetary diffusion coefficient parallel to the magnetic field increases slowly with heliocentric distance.

Mccarthy, J.↗
NASA NTRS1976

Observations of interaction regions and corotating shocks between one and five AU - Pioneers 10 and 11

Interaction regions between adjacent solar-wind streams have been identified between 1 and 5 AU by Pioneer 10 and 11 magnetic-field and plasma measurements. Beyond 1 AU, a relatively large fraction of the interaction regions have been found to be accompanied by either forward shocks, reverse shocks, or shock pairs. The observations are consistent with previous theoretical proposals that the interaction between adjacent streams leads to the development of corotating interplanetary shocks.

Smith, E. J.↗
NASA NTRS1976

Interplanetary shocks seen by Ames plasma probe on Pioneer 6 and 7

Interplanetary shocks and discontinuities observed by the Ames Research Center plasma probe on Pioneer 6 and 7 are analyzed with Goddard Space Flight Center magnetometer data. Several shock normals are used for the MHD model of a shock where the mixed data shock normals, which use plasma and magnetic-field data, give the best agreement with the theoretical requirements. The requirements are the satisfaction of the Rankine-Hugoniot conservation equations across the shock where angles (predicted theoretically from the conservation equations) between certain combinations of plasma and magnetic-field data vectors in the shock normals are explicitly checked. The results for the August 29, 1966, shock are compared with previous results.

Abraham-Shrauner, B.↗