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  • INSTRUMENTATION AND PHOTOGRAPHY  (110)
  • 1995-1999
  • 1980-1984
  • 1975-1979  (110)
  • 1979  (46)
  • 1976  (64)
  • 1
    Publication Date: 2011-08-17
    Description: Described in detail is a laser induced fluorescence system which has been successfully interfaced with two aircraft sampling platforms (i.e., Sabreliner jet and an L-188C Electra). This system, which has been under development for four years, presently consists of the following major components: (1) a Nd-Yag laser driven oscillator-amplifier dye laser; (2) a sampling manifold with associated fluorescence detection optics; (3) an OH calibration chamber; (4) a laser beam steering assembly; and (5) sampling electronics and data processing hardware. During the last three years, this system has been flown some 50,000 air miles making tropospheric OH radical measurements over the latitude range of 70 N to 57 S. OH concentrations measured during these flights have ranged from 30 parts-per-quadrillion (3.7 x 10 to the 5th molecules/sq cm) at altitudes of 6 km to 0.8 parts-per-trillion (2.0 x 10 to the 7th molecules/sq cm) at 0.5 km. Computations have been completed which indicate that the existing aircraft system with modest modifications should also be capable of detecting natural tropospheric levels of NO, SO2, CH2O, NO2, HNO2, NO3, H2O2 and CS2 by using both conventional laser-induced fluorescence methodology and multiphoton techniques.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 50; Dec. 197
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  • 2
    Publication Date: 2019-06-27
    Description: Measurements obtained with laser velocimetry in a Mach 2.9 separated turbulent boundary layer and in the transonic flow past a two-dimensional airfoil section are presented and compared to data realized by conventional techniques. Agreement in mean velocities was realized where the pressure measurements could be considered reliable; however, in regions of instantaneous reverse velocities, the laser results were found to be consistent with the physics of the flow whereas the pressure data were not. Streamwise turbulence intensities are also presented. In the transonic airfoil study, velocity measurements obtained immediately outside the upper surface boundary layer of a 6-inch chord NACA 64A010 airfoil are compared to edge velocities inferred from surface pressure measurements. For free-stream Mach numbers of 0.6 and 0.8, the agreement in results was very good. "Dual scatter" optical arrangements in conjunction with a single particle, counter-type signal processor were employed in these investigations.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TM-X-73117 , A-6510
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  • 3
    Publication Date: 2019-07-13
    Description: Wind tunnel investigations of a shock-induced separated flow and the flow about a two-dimensional airfoil section at transonic speeds using laser velocimetry techniques are described. Laser velocimeter data are presented and compared with conventional pressure type measurements (pitot and static pressure probe measurements for the shock-induced separation, and surface pressure measurements for the two-dimensional airfoil section). In addition to these data comparisons, a simple optical arrangement for the incorporation of a Bragg cell in a laser velocimeter system is described. The effects of particle concentration gradients within a turbulent boundary layer on laser velocimeter measurements are also demonstrated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Minnesota Symposium on Laser Anemometry; Oct 22, 1975 - Oct 24, 1975; Bloomington, MN
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  • 4
    Publication Date: 2011-08-17
    Description: Two CCD techniques were discussed for performing an N-point sampled data correlation between an input signal and an electronically programmable reference function. The design and experimental performance of an implementation of the direct time correlator utilizing two analog CCDs and MOS multipliers on a single IC were evaluated. The performance of a CCD implementation of the chirp z transform was described, and the design of a new CCD integrated circuit for performing correlation by multiplication in the frequency domain was presented. This chip provides a discrete Fourier transform (DFT) or inverse DFT, multipliers, and complete support circuitry for the CCD CZT. The two correlation techniques are compared.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: JPL Conf. on Charge-Coupled Device Technol. and Appls.; 6 p
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  • 5
    Publication Date: 2011-08-16
    Description: The rationale for a Water Vapor Radiometer (WVR) as an aid in predicting tropospheric delay correction is presented. Included is a block diagram and a description of the present developmental WVR with the semiautomated operating sequence outlined. A brief summary of field tests at El Monte airport and Pt. Mugu is given.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: The Deep Space Network; p 77-84
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  • 6
    Publication Date: 2011-08-17
    Description: A discussion is presented of the Deep Space Network water vapor radiometer by means of simultaneous antenna temperature and radiosonde measurements at Edwards Air Force Base. The calibration of radiometer gain and hot load radiometric noise temperature is also described. Calibration equations are given. It is found that with a selected data set, the RMS error is less than 1 cm over a total delay range of 9 to 38 cm. Limitations on the use of the water vapor radiometer are also given.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: The Deep Space Network; p 136-145
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  • 7
    Publication Date: 2019-06-27
    Description: A sealed position sensitive proportional counter filled with two atmospheres of 95% xenon and 5% methane, and containing a drift region of 24 atm cm, has operated in a stable manner for many months. The detector contains G-10 frames to support the anode and cathode wires. The detector was sealed successfully by a combination of vacuum baking the G-10 frames at 150 C for two weeks followed by assembly into the detector in an environment of dry nitrogen, and the use of passive internal getters. The counter is intended for use with a circumferential cylindrical collimator. Together they provide a very broad field of view detection system with the ability to locate cosmic hard X-ray and soft gamma ray sources to an angular precision of a minute of arc. A set of instruments based on this principle have been proposed for satellites to detect and precisely locate cosmic gamma ray bursts.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 8
    Publication Date: 2019-06-27
    Description: The invention comprises of a pair of readout ring electrodes which are used in conjunction with apparatus for measuring the electrical impedance between different points in the body of a living animal to determine the amount of blood flow therebetween. The readout electrodes have independently adjustable diameters to permit attachment around different parts of the body between which it is desired to measure electric impedance. The axial spacing between the electrodes is adjusted by a pair of rods which have a first pair of ends fixedly attached to one electrode and a second pair of ends slidably attached to the other electrode. Indicia are provided on the outer surface of the ring electrodes and on the surface of the rods to permit measurement of the circumference and spacing between the ring electrodes.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 9
    Publication Date: 2019-06-27
    Description: Formulations are presented that permit prediction of image quality as a function of camera performance, surface radiance properties, and lighting and viewing geometry. Predictions made for a wide range of surface radiance properties reveal that image quality depends strongly on proper camera dynamic range command and on favorable lighting and viewing geometry. Proper camera dynamic range commands depend mostly on the surface albedo that will be encountered. Favorable lighting and viewing geometries depend mostly on lander orientation with respect to the diurnal sun path over the landing site, and tend to be independent of surface albedo and illumination scattering function. Side lighting with low sun elevation angles (10 to 30 deg) is generally favorable for imaging spatial details and slopes, whereas high sun elevation angles are favorable for measuring spectral reflectances.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-TN-D-8148 , L-10626
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  • 10
    Publication Date: 2019-07-13
    Description: A position-sensitive proportional counter capable of imaging X-rays (0.1-3 keV) over a 10 cm x 10 cm aperture has been constructed. Positioning is obtained by sensing the signals induced by an X-ray event on the two orthogonal sets of cathode wires. Each cathode is divided into a series of cathode strips, each 0.5 cm wide. An X-ray event induces signals on several adjacent strips. Signals from each cathode strip are amplified separately and then added in an equally weighted and an unequally weighted summing amplifier. The position in each direction is obtained by dividing the output of the unequally weighted summer by that of the equally weighted summer. At 0.94 keV, the accuracy of the position sensing is 190 microns. At the same energy, the energy resolution is approximately 65% (FWHM). The proportional counter system is currently being incorporated into a sounding rocket payload having metal mirror optics, which is being constructed by the X-ray astronomy group at the California Institute of Technology.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Space optics: Imaging X-ray optics workshop; May 22, 1979 - May 24, 1979; Huntsville, AL
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