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  • 1
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    Galileo infrared imaging spectrometry measurements at the Moon (1994)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Imaging spectrometer observations were made of the surface of the Moon during the December 1990 flyby of the Earth-Moon system by the Galileo spacecraft. This article documents this data set and presents analyses of some of the data. The near infrared mapping spectrometer (NIMS) investigation obtained 17 separate mosaics of the Moon in 408 spectral channels between about 0.7 and 5.2 micrometers. The instrument was originally designed to operate in orbit about Jupiter and therefore saturates at many spectral channels for most measurement situations at 1 AU. However, sufficient measurements were made of the Moon to verify the proper operation of the instrument and to demonstrate its capabilities. Analysis of these data show that the NIMS worked as expected and produced measurements consistent with previous ground-based telescopic studies. These are the first imaging spectrometer measurements of this type from space for the Moon, and they illustrate several major points concerning this type of observation and about the NIMS capabilities specifically. Of major importance are the difference between framing and scanning instruments and the effects of the spacecraft and the scan platform on the performance of such and experiment. The science return of subsequent NIMS and other investigation measurements will be significantly enhanced by the experience and results gained.
    Schlagwort(e): ASTRONOMY
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 99; E3; p. 5,587-5,600
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  • 2
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    Concept for a lunar array for very low frequency radio astronomy (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: We discuss the design considerations relevant to a very low frequency array, to be deployed on the lunar near side during an early expedition. Such an array would operate in the frequency range 1-10 MHz, and would consist nominally of 20 antennas distributed over a region approximately 40 km in extent. Each antenna station would consist of a crossed-dipole antenna, together with a receiver, digitizer, solar cells, and batteries. In addition, the station will contain a UHF transmitter for relaying the digitized signal to a central station where it will be transmitted to Earth for subsequent processing, including cross-correlation with signals from other antennas. Each antenna station (including the central station) would be deployed as a self-contained unit, mounted on a miniature robotic vehicle. No fixed structures are required for the array.
    Schlagwort(e): GROUND SUPPORT SYSTEMS AND FACILITIES (SPACE)
    Materialart: In: Engineering, construction, and operations in space - III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 2 (A93-41976 17-12); p. 1935-1940.
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  • 3
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    A miniature high-resolution accelerometer utilizing electron tunneling (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: New methods have been developed to implement high-resolution position sensors based on electron tunneling. These methods allow miniaturization while utilizing the position sensitivity of electron tunneling to give high resolution. A single-element tunneling accelerometer giving a displacement resolution of 0.002 A/sq rt Hz at 10 Hz, corresponding to an acceleration resolution of 5 x 10 exp -8 g/sq rt Hz, is described. A new dual-element tunneling structure which overcomes the narrow bandwidth limitations of a single-element structure is described. A sensor with an operating range of 5 Hz to 10 kHz, which can have applications as an acoustic sensor, is discussed. Noise is analyzed for fundamental thermal vibration of the suspended masses and is compared to electronic noise. It is shown that miniature tunnel accelerometers can achieve resolution such that thermal noise in the suspended masses is the dominant cause of the resolution limit. With a proof mass of order 100 mg, noise analysis predicts limiting resolutions approaching 10 exp -9 g/sq rt Hz in a 300 Hz band and 10 exp -8 g/sq rt Hz at 1 kHz.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: ; : International Conf
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  • 4
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    Low-frequency scattering from cylindrical structures at oblique incidence (1990)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Classical Rayleigh scattering theory is extended to the case of a homogeneous dielectric cylinder of arbitrary cross section whose transverse dimensions are much smaller than the wavelength. By assuming that the surface fields can be approximated by those of the infinite cylinder, the far zone scattered field is expressed in terms of polarizability tensors, whose properties are discussed. Numerical results are presented for circular, semicircular, triangular, and square cylinders. The results are applicable to the remote sensing of twigs, stalks, and vegetation needles at centimeter and millimeter wavelengths.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 28; 879-885
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  • 5
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    Frequency stability of GPS NAVSTAR block 1 and block 2 on-orbit clocks (1992)
    In:  CASI
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    Publikationsdatum: 2013-08-29
    Beschreibung: Analysis of the frequency stability of the on-orbit NAVSTAR clocks os performed by the Naval Research Laboratory. The frequency stability is presented for sample times of one day to 30 days. Composite frequency stability profiles are presented for Block 1 and Block 2 NAVSTAR clocks. Several NAVSTAR cesium clocks show frequency stabilities of a few parts in 1 x 10(exp 14) for long sample times. Time-domain noise-process analysis shows the dominant noise type to be white frequency noise for sample times of one to ten days. The non-stationary stochastic behavior of one of the cesium clocks, illustrated by its frequency stability history, shows that the frequency stability is not always time-invariant.
    Schlagwort(e): PHYSICS (GENERAL)
    Materialart: NASA. Goddard Space Flight Center, Proceedings of the 23rd Annual Precise Time and Time Interval (PTTI) Applications and Planning Meeting; p 307-31
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  • 6
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    Human factors issues in telerobotic systems for Space Station Freedom servicing (1990)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Requirements for Space Station Freedom servicing are described and the state-of-the-art for telerobotic system on-orbit servicing of spacecraft is defined. The projected requirements for the Space Station Flight Telerobotic Servicer (FTS) are identified. Finally, the human factors issues in telerobotic servicing are discussed. The human factors issues are basically three: the definition of the role of the human versus automation in system control; the identification of operator-device interface design requirements; and the requirements for development of an operator-machine interface simulation capability.
    Schlagwort(e): MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Materialart: NASA, Lyndon B. Johnson Space Center, Third Annual Workshop on Space Operations Automation and Robotics (SOAR 1989); p 485-492
    Format: application/pdf
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  • 7
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    DSN co-observing operations to support space VLBI missions (1994)
    In:  CASI
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    Publikationsdatum: 2013-08-31
    Beschreibung: Reliable radio astronomy support of space very long baseline interferometry (VLBI) missions by ground radio telescopes is mandatory in order to achieve a high scientific return from the missions. The 70 m DSN antennas along with other ground radio telescopes will perform as the ground segment of the earth-space interferometer. Improvements of radio astronomy VLBI operations at the DSN to achieve higher reliability, efficiency, flexibility, and lower operations costs is a major goal in preparing for radio astronomy support of SVLBI. To help realize this goal, a remote control and monitoring mode for radio astronomy operations at the DSN has been developed.
    Schlagwort(e): SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Materialart: NASA. Goddard Space Flight Center, Third International Symposium on Space Mission Operations and Ground Data Systems, Part 2; p 767-772
    Format: application/pdf
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  • 8
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    The Orbiter Stability Experiment on STS-40 (1992)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The Orbiter Stability Experiment (OSE) was developed to evaluate the steadiness of the STS Orbiter as a potential platform for instrumentation that would image the Sun in its extreme ultraviolet and soft X-ray radiations. We were interested in any high frequency motions of the Orbiter's orientation due to normal operations and manned activities. Preliminary results are presented of the observations. Other than the expected slow motion of the Orbiter within the specified angular deadband of 0.1 degrees during the observations, it was found that high frequency (above 1 Hz) angular motions (jitter) were not detectable at the 0.25 arc sec detection limit of the most sensitive detector, for most of the period of observation. No high frequency motions were recorded during intervals that were identified with vernier thruster firings. However, one short interval with detectable spectral power to a frequency of 10 Hz has been found to date. It has not yet been correlated with a particular activity going on at the time. The results of the observations may also be of value in assessing perturbations to the Orbiter's micro-gravity environment produced by normal operations.
    Schlagwort(e): SPACE TRANSPORTATION
    Materialart: The 1992 Shuttle Small Payloads Symposium; p 1-8
    Format: application/pdf
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  • 9
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    Plan recognition and generalization in command languages with application to telerobotics (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A method for pragmatic inference as a necessary accompaniment to command languages is proposed. The approach taken focuses on the modeling and recognition of the human operator's intent, which relates sequences of domain actions ('plans') to changes in some model of the task environment. The salient feature of this module is that it captures some of the physical and linguistic contextual aspects of an instruction. This provides a basis for generalization and reinterpretation of the instruction in different task environments. The theoretical development is founded on previous work in computational linguistics and some recent models in the theory of action and intention. To illustrate these ideas, an experimental command language to a telerobot is implemented. The program consists of three different components: a robot graphic simulation, the command language itself, and the domain-independent pragmatic inference module. Examples of task instruction processes are provided to demonstrate the benefits of this approach.
    Schlagwort(e): COMPUTER PROGRAMMING AND SOFTWARE
    Materialart: IEEE Transactions on Systems, Man, and Cybernetics (ISSN 0018-9472); 21; 327-338
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  • 10
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    The present state and future direction of second order closure models for compressible flows (1992)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-29
    Beschreibung: The topics are presented in viewgraph form and include: (1) Reynolds stress closure models; (2) Favre averages and governing equations; (3) the model for the deviatoric part of the pressure-strain rate correlation; (4) the SSG pressure-strain correlation model; (5) a compressible turbulent dissipation rate model; (6) variable viscosity effects; (7) near-wall stiffness problems; (8) models of the Reynolds mass and heat flux; and (9) a numerical solution of the compressible turbulent transport equation.
    Schlagwort(e): FLUID MECHANICS AND HEAT TRANSFER
    Materialart: NASA. Lewis Research Center, Workshop on Engineering Turbulence Modeling; p 249-275
    Format: text
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