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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 649 records · Page 36
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NASA NTRS1972

Analysis and design of a capsule landing system and surface vehicle control system for Mars exporation

The problems related to the design and control of a mobile planetary vehicle to implement a systematic plan for the exploration of Mars were investigated. Problem areas receiving attention include: vehicle configuration, control, dynamics, systems and propulsion; systems analysis; navigation, terrain modeling and path selection; and chemical analysis of specimens. The following specific tasks were studied: vehicle model design, mathematical modeling of dynamic vehicle, experimental vehicle dynamics, obstacle negotiation, electromechanical controls, collapsibility and deployment, construction of a wheel tester, wheel analysis, payload design, system design optimization, effect of design assumptions, accessory optimal design, on-board computer subsystem, laser range measurement, discrete obstacle detection, obstacle detection systems, terrain modeling, path selection system simulation and evaluation, gas chromatograph/mass spectrometer system concepts, chromatograph model evaluation and improvement and transport parameter evaluation.

Frederick, D. K.↗
NASA NTRS1972

Measurement of physical librations using laser retroreflectors.

Discussion of the applicability to lunar physics of the libration measurements obtained from the Apollo lunar laser ranging experiment, and assessment of the data obtained with respect to their adequacy for providing the desired information. A review of measurement principles and lunar properties is followed by an evaluation of the status of data collection.

Mulholland, J. D.↗
NASA NTRS1972

Analysis and design of a capsule landing system and surface vehicle control system for Mars exploration

Investigation of problems related to the design and control of a mobile planetary vehicle to implement a systematic plan for the exploration of Mars has been undertaken. Problem areas receiving attention include: vehicle configuration, control, dynamics, systems and propulsion; systems analysis; terrain modeling and path selection; and chemical analysis of specimens. The following specific tasks have been under study: vehicle model design, mathematical modeling of a dynamic vehicle, experimental vehicle dynamics, obstacle negotiation, electromechanical controls, collapsibility and deployment, construction of a wheel tester, wheel analysis, payload design, system design optimization, effect of design assumptions, accessory optimal design, on-board computer sybsystem, laser range measurement, discrete obstacle detection, obstacle detection systems, terrain modeling, path selection system simulation and evaluation, gas chromatograph/mass spectrometer system concepts, chromatograph model evaluation and improvement.

Frederick, D. K.↗
NASA NTRS1973

Results of Mariner Mars tracking calibration experiment

Ground station network S-band tracking in three-way Doppler modes of Mariner 9 in deep space provided geodetic parameters with an accuracy of 15 meters for use in Apollo 16 and Apollo 17 programs. It was concluded that unified S-band Doppler data provide geodetic results with accuracies comparable to laser ranging data.

Ryan, J. W.↗
NASA NTRS1973

A determination of the earth tidal amplitude and phase from the orbital perturbations of the Beacon Explorer C spacecraft

An analysis of the orbital inclination of the Beacon Explorer C spacecraft over a period of nearly five months in 1970 revealed a very clear and distinctive perturbation caused by the earth and ocean tides. The perturbation has a full amplitude of about 1.8 seconds of arc and a period of about 85 days. This amplitude is approximately 15% smaller than would be expected from the solid-earth tide alone and is shifted slightly in phase. The perturbation can be represented almost exactly by a Love number of k sub 2 = 0.245 with a phase lag of 3.2 degrees. The data used were laser range measurements obtained by a NASA Goddard Space Flight Center tracking system in Greenbelt, Maryland.

Smith, D. E.↗
NASA NTRS1972

Geodesy results obtainable with lunar retroreflectors.

Retroreflector packages have been carried to the moon by the Apollo 11, Apollo 14, and Apollo 15 missions, as well as by Luna 17. Laser ranging from the earth onto these packages should eventually yield information on polar motions and crustal movements accurate to a few centimeters, and on UT1 to 100 microsec. Present (1971) error of the range measurements is 30 cm, but accuracy to 3 cm should be obtainable with improvements in methods and equipment.

Faller, J. E.↗
NASA NTRS1972

Pole position studied with artificial earth satellites.

Long-arc orbit computation of highest accuracy can provide pole positions. Optical Baker-Nunn and laser range observations of several satellites are combined. The accuracy of the pole position is comparable to that of the mean satellite-tracking station coordinates (plus or minus 5 m) when sufficient tracking data are available. Exploitation of the technique requires more accurate tracking data.

Gaposchkin, E. M.↗
NASA NTRS1973

Analysis and design of a capsule landing system and surface vehicle control system for Mars exploration

Problems related to the design and control of a mobile planetary vehicle to implement a systematic plan for the exploration of Mars are reported. Problem areas include: vehicle configuration, control, dynamics, systems and propulsion; systems analysis, terrain modeling and path selection; and chemical analysis of specimens. These tasks are summarized: vehicle model design, mathematical model of vehicle dynamics, experimental vehicle dynamics, obstacle negotiation, electrochemical controls, remote control, collapsibility and deployment, construction of a wheel tester, wheel analysis, payload design, system design optimization, effect of design assumptions, accessory optimal design, on-board computer subsystem, laser range measurement, discrete obstacle detection, obstacle detection systems, terrain modeling, path selection system simulation and evaluation, gas chromatograph/mass spectrometer system concepts, and chromatograph model evaluation and improvement.

Frederick, D. K.↗
NASA NTRS1973

Gradient estimates from stereo measurements for a Martian vehicle

The Martian roving vehicle requires an autonomous obstacle detection and path selection system. A laser range finder will be used to determine the locations of a number of discrete points at distances of 3 to 30 meters from the vehicle. The system might measure angles, ranges or a combination of both types of measurements.

Pfeifer, W. J.↗
NASA NTRS1973

Earth's gravity field to the eighteenth degree and geocentric coordinates for 104 stations from satellite and terrestrial data

Geodetic parameters describing the earth's gravity field and the positions of satellite-tracking stations in a geocentric reference frame were computed. These parameters were estimated by means of a combination of five different types of data: routine and simultaneous satellite observations, observations of deep-space probes, measurements of terrestrial gravity, and surface-triangulation data. The combination gives better parameters than does any subset of data types. The dynamic solution used precision-reduced Baker-Nunn observations and laser range data of 25 satellites. Data from the 49-station National Oceanic and Atmospheric Administration BC-4 network, the 19-station Smithsonian Astrophysical Observatory Baker-Nunn network, and independent camera stations were employed in the geometrical solution. Data from the tracking of deep-space probes were converted to relative longitudes and distances to the earth's axis of rotation of the tracking stations. Surface-gravity data in the form of 550-km squares were derived from 19,328 1 deg X 1 deg mean gravity anomalies.

Gaposchkin, E. M.↗
NASA NTRS1973

The 1973 Smithsonian standard earth (3)

The origins of the satellite geodesy program are described, starting with the International Geophysical Year, continuing through a number of international programs, and culminating with the National Geodetic Satellite Program. The philosophical basis for the Baker-Nunn camera and the laser ranging system, the evolution of international scientific cooperation, and the significance of the results are discussed.

Garoschkin, E. M.↗
NASA NTRS1974

Error analysis for station position from tracking of the Lageos satellite

The earth physics satellite systems error analysis program was applied to the problem of predicting the relative accuracy of station position determinations under varying orbital and observing geometries. The reference case consists of nine ground stations extending over 1500 km which lasers ranged to a LAGEOS satellite, with simultaneous Doppler tracking from a geosynchronous satellite for 16 days. Eleven variations from the reference case were tested. The results showed little sensitivity to whether the LAGEOS altitude is 3700 or 5690 km. More significant were the high inclination, and that LAGEOS was tracked by a geosynchronous satellite.

Parmenter, M. E.↗
NASA NTRS1973

Selenographic control

Evaluation of selenographic data obtained with use of different observational means requires the formulation of rigorous algorithms connecting the systems of coordinates, which the various methods have been referred to. The lunar principal axes of inertia are suggested as most appropriate for reference in lunar mapping and selenographic coordinate catalogues. The connection between the instantaneous axis of lunar rotation (involved in laser ranging, radar studies, astronomical observations from the surface of the moon and VLBI observations of ALSEPs), the ecliptic system of coordinates (which in reductions of observations was considered as fixed in space), the 'Cassini' mean selenographic coordinates (to which physical libration measures were referred), the lunar principal axes of inertia, and the invariable plane of the solar system is discussed.

Moutsoulas, M. D.↗
NASA NTRS1973

Some effects of elasticity on lunar rotation

A general Hamiltonian for a rotating moon in the field of the earth is expanded in terms of parameters orienting the spin angular momentum relative to the principal axes of the moon and relative to coordinate axes fixed in the orbital plane. The effects of elastic distortion are included as modifications of the moment of inertia tensor, where the magnitude of the distortion is parameterized by the Love number k2. The amplitudes of the principal periodic terms in the longitude of a point on the moon due to variations of the tide caused by the earth are discussed. A detailed derivation of the free wobble of the lunar spin axis about the axis of maximum moment of inertia is given. If the moon's rigidity is close to that of the earth there is no effect of elasticity on the rotation which can be measured with the laser ranging and, therefore, no elastic properties of the moon can be determined from variations in the rotation.

Peale, S. J.↗
NASA NTRS1973

Orientation of the moon by numerical integration

The differential equations of rotational motion of the moon are solved by numerical integration methods. Euler's dynamical equations transformed to a convenient form are treated by techniques analogous to ordinary orbit determination procedures. The proposed method is fully consistent with the ephemeris of the moon and can utilize a variety of observational material for the solution of the selected parameters. Examples are given of comparison between the proposed method and Eckhardt's 1970 model of the physical librations of the moon. The merits of the new method are discussed in the light of conventional data sources like earth-based or satellite-based photography as well as newly available data types like laser ranging to retroreflectors on the moon.

Papo, H. B.↗
NASA NTRS1974

Station coordinates for GEOS-C altimeter calibration and experimentation

Station coordinates are given for the C-band radar GEOS-C altimeter calibration sites at Bermuda, Merritt, Grand Turk, and Wallops Islands. The coordinates were estimated in a multi-arc dynamic solution using GEOS-2 C-band radar and laser ranges with a priori information from the GSFC-1973 station coordinate solution. Comparisons with other solutions suggest a relative uncertainty of a few meters in each coordinate. Data reductions show that station coordinates of this quality can introduce a rapidly changing error into the altitude of a satellite whose orbit is determined from calibration area data alone. In contrast, global tracking constrains the orbit and results in slowly varying satellite position error.

Marsh, J. G.↗