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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Galileo Jupiter approach orbit determination

Orbit determination characteristics of the Jupiter approach phase of the Galileo mission are described. Predicted orbit determination performance is given for the various mission events that occur during Jupiter approach. These mission events include delivery of an atmospheric entry probe, acquisition of probe science data by the Galileo orbiter for relay to earth, delivery of an orbiter to a close encounter of the Galilean satellite Io, and insertion of the orbiter into orbit about Jupiter. The orbit determination strategy and resulting accuracies are discussed for the data types which include Doppler, range, optical imaging of Io, and a new Very Long Baseline Interferometry (VLBI) data type called Differential One-Way Range (DOR).

Miller, J. K.↗
NASA NTRS1985

Theoretical Thermodynamics of Mixtures at High Pressures

The development of an understanding of the chemistry of mixtures of metallic hydrogen and abundant, higher-z material such as oxygen, carbon, etc., is important for understanding of fundamental processes of energy release, differentiation, and development of atmospheric abundances in the Jovian planets. It provides a significant theoretical base for the interpretation of atmospheric elemental abundances to be provided by atmospheric entry probes in coming years. Significant differences are found when non-perturbative approaches such as Thomas-Fermi-Dirac (TFD) theory are used. Mapping of the phase diagrams of such binary mixtures in the pressure range from approx. 10 Mbar to approx. 1000 Mbar, using results from three-dimensional TFD calculations is undertaken. Derivation of a general and flexible thermodynamic model for such binary mixtures in the relevant pressure range was facilitated by the following breakthrough: there exists an accurate nd fairly simple thermodynamic representation of a liquid two-component plasma (TCP) in which the Helmholtz free energy is represented as a suitable linear combination of terms dependent only on density and terms which depend only on the ion coupling parameter. It is found that the crystal energies of mixtures of H-He, H-C, and H-O can be satisfactorily reproduced by the same type of model, except that an effective, density-dependent ionic charge must be used in place of the actual total ionic charge.

Hubbard, W. B.↗
NASA NTRS1984

A Shuttle free flyer qualification/acceptance program - Galileo

The next U.S. planetary mission, the Galileo Project, is to be launched in late spring 1986. Primary studies to be conducted are related to the chemical composition and physical state of Jupiter's atmosphere, the chemical composition and physical state of the Jovian satellites, and the structure and physical dynamics of the Jovian magnetosphere. The studies are to be performed with the aid of a planetary Orbiter and an atmospheric entry Probe. At launch and during the interplanetary cruise trip to Jupiter, the Orbiter and Probe will form an integrated spacecraft. The Shuttle will be employed in the launch of the spacecraft. A Centaur high energy upper stage is to transfer the spacecraft from the Shuttle parking orbit to the direct earth-to-Jupiter trajectory. Attention is given to Galileo environmental program special characteristics and major influencing factors.

Schlue, J. W.↗
NASA NTRS1986

Mesoscale waves as a probe of Jupiter's deep atmosphere

Images from the Voyager north/south mapping sequences were searched for waves. A remarkable class of mesoscale waves was identified, with the following features: (1) the wavetrains are usually aligned zonally, i.e., wavecrests are north-south; (2) the average wavelength is 300 km with a standard deviation of only 20%; (3) the wavetrains are long; (4) the waves occur within 25 degrees of the equator, the bulk being at the equator itself; (5) the waves are centered at the extrema (in latitude) of the zonal flow; and (6) the meridional extent of the waves is typically 1 degree of latitude. These observations are interpreted as evidence of gravity waves propagating vertically within a leaky duct. A three-level model is assumed composed of a stable duct which extends up to the base of the NH3 cloud deck near 600 mb. Above this is a thin wave-trapping region characterized by a Richardson number Ri less than 1/4 and containing a critical level, where the local value of the zonal flow velocity equals the phase speed of the wave. This in turn is overlain by a stable region, representing the tropopause region and stratosphere.

Flaser, F. M.↗
NASA NTRS1986

Mesoscale waves as a probe of Jupiter's deep atmosphere

Search of the Voyager images of Jupiter reveals a class of mesoscale waves occurring near the extrema of the zonal velocity profile between latitudes 30 deg S and 30 deg N. The average horizontal wavelength is 300 km, compared to an atmospheric scale height of 20 km; the standard deviation about the mean is only 20 percent. The alignment of most wave trains is nearly zonal, i.e., wave crests are north-south. A typical wave packet is 20 wave crests in length and 1300 km wide. Modeling shows that the waves propagate in a duct below the ammonia condensation level (the visible clouds). For selection of one dominant mode, the Richardson number in the duct must be of order unity; this is the first quantitative determination that has ever been made of the stability of Jupiter's atmosphere below its clouds. The duct is topped by a trapping layer, the ammonia clouds, where the Richardson number is less than 0.25. Meridional trapping of the wave packets is due to the shear in the zonal wind. It is speculated that the period of the waves is diurnal and that they do not propagate poleward of latitudes + or - 30 deg because the Coriolis frequency exceeds the duct Brunt frequency. The waves might be excited by diurnal variations of moist convective activity in the ammonia clouds.

Flasar, F. M.↗
NASA NTRS1985

The Galileo attitude and articulation control system - A radiation-hard, high precision, state-of-the-art control system

The Galileo mission and spacecraft, consisting of a Jupiter-orbiter and an atmospheric entry probe, are discussed. Components will include: magnetometers and plasma-wave antennas on a boom, high-gain antenna, probe vehicle, two different bus electronics packages, and a radioisotope thermoelectric generator. Instruments, investigators and objectives are tabulated for both probe science and orbiter science investigations. Requirements in the design of the attitude and articulation control system are very stringent because of the complex dynamics, flexible body effects, the need for autonomy, and the severe radiation environment in the Jupiter nighborhood. Galileo was intended to be ready for launch via Space Shuttle in May of 1986.

Stephenson, R. Rhoads↗
NASA NTRS1988

Multiple-Diode-Laser Gas-Detection Spectrometer

Small concentrations of selected gases measured automatically. Proposed multiple-laser-diode spectrometer part of system for measuring automatically concentrations of selected gases at part-per-billion level. Array of laser/photodetector pairs measure infrared absorption spectrum of atmosphere along probing laser beams. Adaptable to terrestrial uses as monitoring pollution or control of industrial processes.

Webster, Christopher R.↗
NASA NTRS1988

Observations of ultraviolet variability in RV Tauri stars

An IUE program to monitor the ultraviolet variability in RV Tauri stars was initiated. The Mg II region was investigated as a potential probe of atmospheric shocks, which are believed to be associated with the pulsational variability of this class of objects. Observations, a description of the spectra, and findings for V Vul and AC Her are presented. The Mg II emission does vary significantly during the cycle; major changes in the emission line strength occur on a time scale much less than 0.2 in phase; and as the UV (and optical) continuum flux increases, the Mg II lines decrease and increased emission may be seen at 2823, 2844, and 2900 A.

Brugel, Edward W.↗
NASA NTRS1988

Cassini - A mission to the Saturnian system

This international (NASA/ESA) mission, planned for a Titan IV/Centaur G-prime launch in the 1995-1997 era, consists of a Saturn Orbiter (a U.S. Mariner Mark II spacecraft) and a Titan Atmospheric Entry Probe (an ESA product). The mission profile is highly sophisticated in its astrodynamic aspects - a deep space Delta-V maneuver, followed by earth and Jupiter gravity assist flybys, with asteroid encounter(s) along the way. Saturn arrival is characterized by further multiple maneuvers resulting in the Titan probe delivery and a close orbiter flyby, to be followed by a 4-year Saturn system tour. Details of the trajectory design process are discussed.

Sergeyevsky, Andrey B.↗
NASA NTRS1990

Advanced interdisciplinary technologies

The following topics are presented in view graph form: (1) breakthrough trust (space research and technology assessment); (2) bionics (technology derivatives from biological systems); (3) biodynamics (modeling of human biomechanical performance based on anatomical data); and (4) tethered atmospheric research probes.

Anderson, John L.↗
NASA NTRS1990

Project Galileo

Galileo is now enroute to Jupiter to do its intensive and comprehensive investigation of the Jupiter System. The Galileo Spacecraft consists of a Jupiter Orbiter and an Atmospheric Entry Probe. The Galileo mission at Jupiter is described. The design and operation of the Probe and Orbiter are discussed in some detail. The history of the many Shuttle upper stage changes Galileo experienced during development is outlined. The VEEGA trajectory Galileo is flying to achieve enough energy to reach Jupiter is explained. Science of opportunity on the circuitous VEEGA route is identified. Galileo Mission Operations are described. The paper concludes with an inflight mission status statement.

O'Neil, William J.↗
NASA NTRS1992

Space Science Reviews volume on Galileo Mission overview

The Galileo Mission, rather than a 'Jupiter mission' per se, is an integrated project encompassing multidisciplinary objectives regarding the whole of the Jovian system. This system is important in view of insights it affords into the conditions of the early solar nebula, as well as into the complex, interacting processes involved in planetary evolution. Jupiter itself is the focus of interest in virtue of representing a transitional object between the terrestrial planets and stars; its composition may be virtually unaltered from that of the original solar nebula. The Jovian system in its entirety presents basic questions regarding its satellite and ring system, which constitute a 'minisolar system'. The Galileo spacecraft consists of an Orbiter and an atmospheric entry Probe.

Johnson, T. V.↗
NASA NTRS1995

Exploring small bodies in the outer solar system with stellar occultations

Stellar occultation observations probe the atmospheric structure and extinction of outer solar system bodies with a spatial resolution of a few kilometers, and an airborne platform allows the observation of occultations by small bodies that are not visible from fixed telescopes. Results from occultations by Triton, Pluto, and Chiron observed with KAO are discussed, and future directions for this program are presented.

Elliot, Jim L.↗
NASA NTRS1999

Exploration of the Saturnian System with Cassini Radio Science

The ongoing Galileo mission has provided many new insights into the Jovian system. Among them are new discoveries from the Radio Science investigations , including multiple measurements of the Jovian ionosphere, the ionospheres and plasma environments of Io, Europa, Ganymede, and Callisto, and the internal structure of the Galilean satellites. The Cassini spacecraft, which will be placed in orbit about Saturn in 2004, will conduct Radio Science investigations of many aspects of the Saturnian system with a radio instrument of unprecedented stability and versatility. It will use radio links at three wavelengths : S-band(13 cm), X-band (3.5 cm), and Ka-band (1 cm) to probe the atmospheres and ionospheres of Saturn and Titan and Saturn's rings by means of radio occultations, and to measure the masses and gravity fields of Saturn, Titan, and selected icy satellites by precision tracking. In addition, the stability of the radio instrument will be utilized to conduct a search for gravitational waves during solar oppositions, and to precisely measure general relativistic effects during solar conjunctions during the interplanetary cruise prior to arrival at Saturn.

Kliore, Arvydas J.↗
NASA NTRS1998

A Fast Code for Jupiter Atmospheric Entry

A fast code was developed to calculate the forebody heating environment and heat shielding that is required for Jupiter atmospheric entry probes. A carbon phenolic heat shield material was assumed and, since computational efficiency was a major goal, analytic expressions were used, primarily, to calculate the heating, ablation and the required insulation. The code was verified by comparison with flight measurements from the Galileo probe's entry; the calculation required 3.5 sec of CPU time on a work station. The computed surface recessions from ablation were compared with the flight values at six body stations. The average, absolute, predicted difference in the recession was 12.5% too high. The forebody's mass loss was overpredicted by 5.5% and the heat shield mass was calculated to be 15% less than the probe's actual heat shield. However, the calculated heat shield mass did not include contingencies for the various uncertainties that must be considered in the design of probes. Therefore, the agreement with the Galileo probe's values was considered satisfactory, especially in view of the code's fast running time and the methods' approximations.

Tauber, Michael E.↗
NASA NTRS1999

A Fast Code for Jupiter Atmospheric Entry Analysis

A fast code was developed to calculate the forebody heating environment and heat shielding that is required for Jupiter atmospheric entry probes. A carbon phenolic heat shield material was assumed and, since computational efficiency was a major goal, analytic expressions were used, primarily, to calculate the heating, ablation and the required insulation. The code was verified by comparison with flight measurements from the Galileo probe's entry. The calculation required 3.5 sec of CPU time on a work station, or three to four orders of magnitude less than for previous Jovian entry heat shields. The computed surface recessions from ablation were compared with the flight values at six body stations. The average, absolute, predicted difference in the recession was 13.7% too high. The forebody's mass loss was overpredicted by 5.3% and the heat shield mass was calculated to be 15% less than the probe's actual heat shield. However, the calculated heat shield mass did not include contingencies for the various uncertainties that must be considered in the design of probes. Therefore, the agreement with the Galileo probe's values was satisfactory in view of the code's fast running time and the methods' approximations.

Tauber, Michael E.↗
NASA NTRS2000

Evaluation of Mars Entry Reconstructured Trajectories Based on Hypothetical 'Quick-Look' Entry Navigation Data

A first order simulation analysis of the navigation accuracy expected from various Navigation Quick-Look data sets is performed. Here quick-look navigation data are observations obtained by hypothetical telemetried data transmitted on the fly during a Mars probe's atmospheric entry. In this simulation study, navigation data consists of 3-axis accelerometer sensor and attitude information data. Three entry vehicle guidance types are studied: I. a Maneuvering entry vehicle (as with Mars 01 guidance where angle of attack and bank angle are controlled); II. Zero angle-of-attack controlled entry vehicle (as with Mars 98); and III. Ballistic, or spin stabilized entry vehicle (as with Mars Pathfinder);. For each type, sensitivity to progressively under sampled navigation data and inclusion of sensor errors are characterized. Attempts to mitigate the reconstructed trajectory errors, including smoothing, interpolation and changing integrator characteristics are also studied.

Pastor, P. Rick↗
NASA NTRS1993

Design of the Galileo Satellite Tour

Concepts, strategies, and techniques developed in the 1970s and 1980s, which were used in designing the satellite tour for the 1986 launch opportunity were employed and extended for this effort.

satellite tour↗