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  • 1
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    The vector magnetograph of the Sayan Solar Observatory (1985)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: The problem of choosing an optimum scheme for the electrooptical analyzer of polarization and related control principles are discussed. An electrooptical deflector, which is advantageously used to employ a single photodetector and to remove systematic errors inherent in magnetographs with two photodetectors in the wings of the line is discussed, as well as adjustment errors of optical elements of the polarization analyzer and errors of control voltages. A method for measuring the telescope's polarization matrix, reduction of magnetographic measurements for instrumental polarization and calibration of magnetograph channels are examined. Questions of evaluating scattered light and of reducing magnetic field measurements are also considered as a computational procedure for the magnetic field vector parameters is briefly outlined. Computer control of the solar magnetograph and of the processing and control system software is discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Marshall Space Flight Center Meas. of Solar Vector Magnetic Fields; p 231-256
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  • 2
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    Automatic processing system for shadowgraph and interference patterns (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: The design and operation of an automatic system for the processing of shadowgraph and interference images are described. The system includes a two-coordinate processing table with an optical system for the projection of transparent images onto the photodetector, an image filter in the photodetector field, and a device for controlling the movement of the table and transmitting information to the minicomputer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-88525 , NAS 1.15:88525
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  • 3
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    Photothermoplastic films for holographic recording (1987)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The electrophotographic and sensitometric characteristics of poly-N-vinyl carbazole photothermoplastic films, sensitized by an amorphous-Se sublayer are examined. It is shown that the photosensitivity of the material can be improved and its spectral range can be expanded by sensitization of amorphous Se with additions of Te, As, and Sb; this can be accomplished without a significant reduction in diffraction efficiency and resolving power.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-88574 , NAS 1.15:88574
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  • 4
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    Balloon-borne cryogenic spectrometer for measurement of lower stratospheric trace constituents (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A liquid-nitrogen cooled, multidetector Fourier transform spectrometer has been constructed to measure minor stratospheric constituents via high resolution, earth-limb emission spectroscopy from a balloon-borne platform. Cryogenic cooling, combined with the use of extrinsic silicon photoconductor detectors cooled to liquid-helium temperature, allows the detection of weak emission features of gaseous species. The spectrometer has two basic scan modes: the first mode records the continuous spectrum from 650-2100/cm with 0.2/cm resolution; the second simultaneously records four preselected narrow intervals (about 175/cm bandpass each) with 0.02/cm resolution, unapodized. Filtering of the interferogram signal is done by real-time, digital signal processing. The most important feature of this flat mirror Michelson system, with respect to remote balloon-borne operation, is the dynamic alignment system which maintains the relative parallelism of the two flat reflectors of the interferometer. Species identified to date in data obtained during a Nov. 6, 1984, flight include: CO2, O3, H2O, CH4, HNO3, N2O, NO2, NO, CCl3F (Freon-11) and CF2Cl2 (Freon-12).
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 5
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    Droplet field visualization and characterization via digital image analysis (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: This paper describes techniques that have been developed at JPL for visualization and measurements of droplet fields in a moving airstream. The techniques have been applied to a variety of problems which include simulation of heavy rain conditions in a wind tunnel, engine ingestion of wheel spray, analysis of fuel nozzle sprays and aerodynamic breakup of non-Newtonian liquids. The approach pursued here is direct imaging using a pulsed laser illumination source, followed by digital processing of photographic images. A laser double pulse technique has been used for determination of droplet velocities. Laser induced fluorescence has been used to enhance droplet definition in photographic images. The image processing software developed is capable of distinguishing between out-of-focus and in-focus drops, retaining only the latter for size determination.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 6
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    The laser interferometer skin-friction meter - A numerical and experimental study (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Limits to the applicability of thin-film lubrication theory are established. The following two problems are considered: (1) the response of the oil film to a time-varying skin friction such as is encountered in turbulent boundary layers, and (2) a 'surface-wave instability' encountered at high skin-friction levels. Results corresponding to the first problem reveal that the laser interferometer skin-friction meter may, in principle, be applied to the measurement of instantaneous skin friction. In addressing the second problem, it is shown that the observed surface waves are not the result of a hydrodynamic instability.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Physics E - Scientific Instruments (ISSN 0022-3735); 19; 744-751
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  • 7
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    Measurements with an airborne, autotracking, external-head sunphotometer (1986)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Design and performance features and sample results from use of a NASA airborne tracking sunphotometer (ATS) are described. The ATS was devised to obtain continuous vertical profiles of the optical depth and transmissivity, first from a CV-990 aircraft and then from a modified DC-8 aircraft. Sample results are presented from a 1985 flight as part of the SAGE-II calibration mission, which featured detectors frequencies of 380, 450, 600, 860, 940, and 1020 microns and covered flight altitudes from ground to 10 km.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 8
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    Report of the Special Panel on statistical particle bias problems in laser anemometry (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An account is given of the findings contained in a concensus document compiled by a group of experts on laser anemometry concerning statistical particle bias and its possible remedies. Emphasis is placed on the systematic character of this bias, rather than its magnitude. Since bias errors are a function of flow velocity and turbulence intensity, the measured results may contain apparent trends due solely to the measurement process. Attention is given to the panel's attempt to clear up terminological confusions in the matter of rates, scales, and magnitudes, as well as to its suggested processing methods for the elimination of velocity bias and the remedy of angle bias.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ASME, Transactions, Journal of Fluids Engineering (ISSN 0098-2202); 109; 89-93
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  • 9
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    Postdispersion system for astronomical observations with Fourier transform spectrometers in the thermal infrared (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A postdispersion system for astronomical observations with Fourier transform spectrometers in the thermal infrared has been developed which improves the sensitivity of radiation noise limited observations by reducing the spectral range incident on the detector. Special attention is given to the first-generation blocked impurity band detector. Planetary, solar, and stellar observations are reported.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 28; 139-145
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  • 10
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    Correcting for particle counting bias error in turbulent flow (1985)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An ideal seeding device is proposed generating particles that exactly follow the flow out are still a major source of error, i.e., with a particle counting bias wherein the probability of measuring velocity is a function of velocity. The error in the measured mean can be as much as 25%. Many schemes have been put forward to correct for this error, but there is not universal agreement as to the acceptability of any one method. In particular it is sometimes difficult to know if the assumptions required in the analysis are fulfilled by any particular flow measurement system. To check various correction mechanisms in an ideal way and to gain some insight into how to correct with the fewest initial assumptions, a computer simulation is constructed to simulate laser anemometer measurements in a turbulent flow. That simulator and the results of its use are discussed.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Langley Research Center Wind Tunnel Seeding Systems for Laser Velocimeters; p 13-28
    Format: application/pdf
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