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  • 1
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    The Fabry-Perot Interferometer on Dynamics Explorer (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The Fabry-Perot Interferometer (FPI) on Dynamics Explorer is a remote sensing instrument designed to measure the temperature, meridional wind and density of the metastable atoms O(1S) and O(1D), and the ion O(plus)(2P) in the thermosphere. The measurements are made with a stable, high resolution Fabry-Perot etalon, which performs a wavelength analysis on the light detected from the thermospheric emission features by spatially scanning the interference fringe plane with a multichannel array detector. The wavelength analysis characterizes the Doppler line profile of the emitting species. A sequential altitude scan, performed by a commandable horizon scan mirror, provides a cross-sectional view of the thermodynamic and dynamic state of the thermosphere below the orbit of the Dynamics Explorer B satellite.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: Space Science Instrumentation; 5; Dec. 198
    Format: text
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  • 2
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    Statistical analysis of the modal properties of large structural systems. (1971)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: A theory is developed to predict eigenvalue and eigenvector uncertainty in large dynamic models. The uncertainty is based on physical property uncertainty and should not be confused with numerical roundoff, although the method can be extended to include the latter. The theory, when implemented on a computer, is used to analyze the uncertainties in frequencies and mode shapes based on uncertainties in mass, stiffness, modulus of elasticity, etc. The method incorporates a linear statistical model which is quite adequate for handling property uncertainties of 10% or more. The model is not limited to small systems but uses certain statistical assumptions as well as selective matrix manipulations to keep the size of all matrix operations to within the number of degrees of freedom of the system. Examples are given for two longitudinal vibration problems, and the results are supported by a Monte Carlo analysis.
    Keywords: STRUCTURAL MECHANICS
    Type: SAE PAPER 710785 , Society of Automotive Engineers, National Aeronautic and Space Engineering and Manufacturing Meeting; Sept. 28-30, 1971; Los Angeles, CA
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  • 3
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    Image plane detector for the dynamics explorer Fabry-Perot interferometer (1983)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A compact twelve-channel photon-counting device based on existing Generation II imaging technology has been developed for use as the image-plane detector of the Dynamics Explorer Fabry-Perot interferometer. The device has an S-20 photocathode, three-microchannel plate electron multiplication stages, and an equal-area concentric-ring segmented anode whose geometry mimics that of the interference ring pattern produced by a plane etalon. The twelve channels sample equal and contiguous intervals in the spectrum. The purpose of the delopment has been to utilize the signal multiplex advantage of a multichannel detector in the measurement of Doppler shifts and line-broadening effects for naturally occurring atmospheric emission features of low intensity. The design, testing, calibration, and flight performance of the novel detector system are presented. In addition, measured emission line profiles at high resolution from the satellite instrument are presented to illustrate the operation of the device.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: Applied Optics (ISSN 0003-6935); 22; 3503-351
    Format: text
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  • 4
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    Structural model optimization using statistical evaluation (1972)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The results of research in applying statistical methods to the problem of structural dynamic system identification are presented. The study is in three parts: a review of previous approaches by other researchers, a development of various linear estimators which might find application, and the design and development of a computer program which uses a Bayesian estimator. The method is tried on two models and is successful where the predicted stiffness matrix is a proper model, e.g., a bending beam is represented by a bending model. Difficulties are encountered when the model concept varies. There is also evidence that nonlinearity must be handled properly to speed the convergence.
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-123575
    Format: application/pdf
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  • 5
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    Bending vibrational data accuracy study (1970)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Computer program for predicting structural bending vibrational data
    Keywords: STRUCTURAL MECHANICS
    Type: NASA-CR-102974 , TR-70-1066
    Format: application/pdf
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  • 6
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    Stable and rugged etalon for the Dynamics Explorer Fabry-Perot interferometer. II - Performance (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The etalon is shown to remain stable to less than 5-m/sec equivalent wind over one orbit and less than 100 m/sec over several months in orbit. The thermal stability considerations for the highly stable etalon are discussed, including the passive thermal control used in flight. The various physical processes which give rise to drifts in the peak transmission wavelength are quantified, and the kinematic mount used to isolate the etalon from large incremental forces caused by changes in the thermal environment is presented. The performance of the etalon in its flight configuration is evaluated.
    Keywords: SPACECRAFT INSTRUMENTATION
    Type: Applied Optics; 21; Nov. 1
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  • 7
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    Statistical identification of structures. (1973)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A method is formulated for systematically using experimental measurements of the natural frequencies and mode shapes of a structure to modify stiffness and mass characteristics of a finite element model. Throughout the modification process, which does not require complete data, the finite element model remains consistent. An additional feature is that the engineer's confidence in the modeling of the various finite elements is quantified and incorporated into the revision procedure. Examples demonstrate the convergence and versatility of the method.
    Keywords: STRUCTURAL MECHANICS
    Type: AIAA PAPER 73-339 , Structures, Structural Dynamics, and Materials Conference; Mar 20, 1973 - Mar 22, 1973; Williamsburg, VA; US
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