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  • INSTRUMENTATION AND PHOTOGRAPHY  (55)
  • 1990-1994  (55)
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  • 1991  (55)
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  • 1
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    Charge coupled devices (CCDs) in X-ray astronomy (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The application of CCDs to X-ray imaging and spectroscopy in astronomy is discussed with special attention given to the special requirements of CCDs for X-ray astronomy (as opposed to those for traditional optical applications). The development status of CCDs for X-ray astronomy applications is described, and results of recent research in the area of optimizing the CCD X-ray response are presented. It is shown that very high quantum efficiencies and Fano noise-limited energy resolutions can be obtained using CCDs.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Experimental Astronomy (ISSN 0922-6435); 2; 3 19
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  • 2
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    Long-term changes in the total ozone mapping spectrometer relative to world primary standard Dobson spectrometer 83 (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The stability of the calibration of the Nimbus 7 solar backscatter UV (SBUV) and total ozone mapping spectrometer (TOMS) instruments by comparing their ozone measurements with those made by a single, very stable Dobson instrument: the world primary standard Dobson spectrometer number 83. Measurements of ozone made with instrument 83 at Mauna Loa observatory in eight summers between 1979 and 1989 were compared with coincident TOMS ozone measurements. The comparison shows that relative to instrument 83, ozone measured by TOMS (and SBUV) was stable between 1979 and approximately 1983, had decreased by 3 percent by 1986, and had decreased by almost 7 percent by 1989. A similar time dependence is seen when data from an ensemble of 39 Dobson stations throughout the world is compared with TOMS over the period 1979-1987. The most likely reason for the relative drift is that the diffuser plate used by both SBUV and TOMS to measure solar flux has suffered an uncorrected wavelength-dependent degradation, with most of the degradation occurring after 1983. The recently released version 6 TOMS data, corrected using the internal 'pair justification' technique, show almost no drift relative to Dobson instrument 83. Accurate measurements of long-term global ozone change will require a coherent system incorporating both ground-based and satellite-based ozone measurements.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 2987-299
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  • 3
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    Signal processing considerations for low signal to noise ratio laser Doppler and phase Doppler signals (1991)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The relative performance of current methods used for estimating the phase and the frequency in LDV and phase Doppler applications in low signal to noise ratio conditions is analyzed. These methods include the Fourier analysis and the correlation techniques. Three methods that use the correlation function for frequency and phase estimations are evaluated in terms of accuracy and speed of processing. These methods include: (1) the frequency estimation using zero crossings counting of the auto-correlation function, (2) the Blackman-Tukey method, and (3) the AutoRegressive method (AR). The relative performance of these methods is evaluated and compared with the Fourier analysis method which provides the optimum performance in terms of the Maximum Likelihood (ML) criteria.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Laser anemometry - Advances and applications 1991; Proceedings of the 4th International Conference, Cleveland, OH, Aug. 5-9, 1991. Vol. 2 (A93-23776 08-35); p. 685-692.
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  • 4
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    WTEC panel report on European nuclear instrumentation and controls (1991)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Control and instrumentation systems might be called the 'brain' and 'senses' of a nuclear power plant. As such they become the key elements in the integrated operation of these plants. Recent developments in digital equipment have allowed a dramatic change in the design of these instrument and control (I&C) systems. New designs are evolving with cathode ray tube (CRT)-based control rooms, more automation, and better logical information for the human operators. As these new advanced systems are developed, various decisions must be made about the degree of automation and the human-to-machine interface. Different stages of the development of control automation and of advanced digital systems can be found in various countries. The purpose of this technology assessment is to make a comparative evaluation of the control and instrumentation systems that are being used for commercial nuclear power plants in Europe and the United States. This study is limited to pressurized water reactors (PWR's). Part of the evaluation includes comparisons with a previous similar study assessing Japanese technology.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-198560 , NAS 1.26:198560 , PB92-100197
    Format: application/pdf
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  • 5
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    Electronic considerations for externally segmented germanium detectors (1991)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The dominant background source for germanium gamma ray detector spectrometers used for some astrophysics observations is internal beta decay. Externally segmented germanium gamma ray coaxial detectors can identify beta decay by localizing the event. Energetic gamma rays interact in the germanium detector by multiple Compton interactions while beta decay is a local process. In order to recognize the difference between gamma rays and beta decay events, the external electrode (outside of detector) is electrically partitioned. The instrumentation of these external segments and the consequence with respect to the spectrometer energy signal is examined.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: International Symposium on Gamma-Ray Line Astrophysics; Dec 10, 1990 - Dec 13, 1990; Paris; France
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  • 6
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    NASA's program in lidar remote sensing (1991)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Several major NASA research efforts in lidar remote sensing are reviewed, with attention given to hardware and key sensor issues along with results and expectations. The discussion covers temperature and pressure measurements, measurements methods and instrumentation, pressure data, wind field measurements, atmospheric backscatter measurement, aerosol and cloud measurements, and water vapor measurement. Consideration is also given to the applicability of lidar measurements to problems of operational weather analysis and forecasting, climate studies, mesoscale and severe storm analysis and forecastig, and studies of atmosphere/surface interface.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Earth and atmospheric remote sensing; Proceedings of the Meeting, Orlando, FL, Apr. 2-4, 1991 (A93-24176 08-42); p. 2-23.
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  • 7
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    High-resolution studies of atmospheric IR emission spectra (1991)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: Atmospheric emission spectra obtained with two different spectrometer systems are presented. The first system (the BOMEM Michelson interferometer) is designed for emission work. Spectra were obtained under adverse conditions in the Antarctic, and are still of good absolute accuracy. The second system (a modified Bruker Instruments IFS120 very high spectral resolution interferometer) demonstrates the sensitivity that can be achieved even at higher spectral resolution. This system shows that mid-IR atmospheric emission spectra can be obtained with a good SNR in a reasonable length of time at a relatively high resolution. A properly designed high resolution system should achieve high accuracy, sensitivity, and resolution, thereby permitting measurements of many atmospheric constituents when solar spectra cannot be obtained.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Remote sensing of atmospheric chemistry; Proceedings of the Meeting, Orlando, FL, Apr. 1-3, 1991 (A93-31376 11-35); p. 282-287.
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  • 8
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    Thin film diamond microstructure applications (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: Selective deposition and abrasion, as well as etching in atomic oxygen or reduced-pressure air, have been used to prepare patterned polycrystalline diamond films which, on further processing by anisotropic Si etching, yield the microstructures of such devices as flow sensors and accelerometers. Both types of sensor have been experimentally tested in the respective functions of hot-wire anemometer and both single- and double-hinged accelerometer.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Applications of diamond films and related materials; Proceedings of the 1st International Conference, Auburn, AL, Aug. 17-22, 1991 (A93-40551 16-76); p. 311-318.
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  • 9
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    Aircraft laser infrared absorption spectrometer (ALIAS) for polar ozone studies (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The ALIAS instrument is a very high resolution (0.0003/cm) scanning, tunable diode laser spectrometer designed to make direct, simultaneous measurements of NO2, HNO3, HCl, CH4, and either O3 or N2O (including vertical profiles of CH4 and N2O) in the polar stratosphere at sub-part-per-billion level sensitivities over integration times from 3 to 30 s. Unique features include a sample inlet/throttle system designed to achieve near-isokinetic sampling, in PSC events, an in-flight wavelength reference cell rack, mechanical fringe-spoilers, a four-laser/four-detector dewar with 24-hr hold-time operating at a fixed temperature without electrical regulation, and in-flight fast correlation routines for spectral drift compensation prior to spectral addition. Instrument design and test flight results are discussed in the light of ALIAS's role in the Winter 1991 Arctic aircraft stratospheric ozone campaigns out of Fairbanks, Alaska, and Bangor, Maine.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: Infrared technology XVII; Proceedings of the Meeting, San Diego, CA, July 22-26, 1991 (A93-38376 15-35); p. 187-194.
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  • 10
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    Characteristics of a high pressure gas proportional counter filled with xenon (1991)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The characteristics of a conventional cylindrical geometry proportional counter filled with high pressure xenon gas up to 10 atm. were fundamentally investigated for use as a detector in hard X-ray astronomy. With a 2 percent methane gas mixture the energy resolutions at 10 atm. were 9.8 percent and 7.3 percent for 22 keV and 60 keV X-rays, respectively. From calculations of the Townsend ionization coefficient, it is shown that proportional counters at high pressure operate at weaker reduced electric field than low pressure counters. The characteristics of a parallel grid proportional counter at low pressure showed similar pressure dependence. It is suggested that this is the fundamental reason for the degradation of resolution observed with increasing pressure.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: In: EUV, X-ray, and gamma-ray instrumentation for astronomy II; Proceedings of the Meeting, San Diego, CA, July 24-26, 1991 (A93-34376 13-35); p. 20-27.
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