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  • 1
    Publication Date: 2011-08-16
    Description: Liquid Xe filled single wire proportional and multiple wire ionization chambers, measuring gain and time/spatial resolution properties
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ; 29 (
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  • 2
    Publication Date: 2011-08-16
    Description: We present a new technique for the correction of atmospheric distortion in telescope images. Most of this distortion arises from a random phase variation of the incoming light across the telescope aperture. This variation limits the resolving power of even large telescopes to about one arc second. If the sharpness of the images is defined in a suitable way, this sharpness is maximized only when the phase distortion of the incoming light is zero. We present computer simulations of a simple feedback system in which active optical elements, set to maximize the sharpness, correct most of the atmospheric distortion. Photon statistics set the limiting magnitude of the object for which a practical feedback system can work. Details in a sixth magnitude object smaller than 0.1 sec of arc should be resolvable. The system can be conveniently employed within existing telescopes.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Society of America; vol. 64
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  • 3
    Publication Date: 2011-08-17
    Description: Anisotropy has been detected in the cosmic blackbody radiation with a 33-GHz (0.9 cm) twin-antenna Dicke radiometer flown to an altitude of 20 km aboard a U-2 aircraft. In data distributed over two-thirds of the Northern Hemisphere, an anisotropy is observed, which is well fitted by a first-order spherical harmonic with an amplitude of (3.5 plus or minus 0.6) x 10 to the -3rd deg K, and direction 11.0 plus or minus 0.6 h right ascension and 6 plus or minus 10 deg declination. This observation is readily interpreted as due to motion of the earth relative to the radiation with a velocity of 390 plus or minus 60 km/sec.
    Keywords: SPACE RADIATION
    Type: Physical Review Letters; 39; Oct. 3
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  • 4
    Publication Date: 2013-08-31
    Description: Complex computer generated phase holograms (CGPH's) have been fabricated in PMMA by partial e-beam exposure and subsequent partial development. The CGPH was encoded as a sequence of phase delay pixels and written by the JEOL JBX-5D2 E-beam lithography system, a different dose being assigned to each value of phase delay. Following carefully controlled partial development, the pattern appeared rendered in relief in the PMMA, which then acts as the phase-delay medium. The exposure dose was in the range 20-200 micro-C/sq cm, and very aggressive development in pure acetone led to low contrast. This enabled etch depth control to better than plus or minus lambda(sub vis)/60. That result was obtained by exposing isolated 50 micron square patches and measuring resist removal over the central area where the proximity effect dose was uniform and related only to the local exposure. For complex CGPH's with pixel size of the order of the e-beam proximity effect radius, the patterns must be corrected for the extra exposure caused by electrons scattered back up out of the substrate. This has been accomplished by deconvolving the two-dimensional dose deposition function with the desired dose pattern. The deposition function, which plays much the same role as an instrument response function, was carefully measured under the exact conditions used to expose the samples. The devices fabricated were designed with 16 equal phase steps per retardation cycle, were up to 1 cm square, and consisted of up to 100 million 0.3-2.0 micron square pixels. Data files were up to 500 MB long and exposure times ranged to tens of hours. A Fresnel phase lens was fabricated that had diffraction limited optical performance with better than 85 percent efficiency.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Marshall Space Flight Center, Conference on Binary Optics: An Opportunity for Technical Exchange; p 207-221
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  • 5
    Publication Date: 2011-08-16
    Description: A new type of gamma-ray camera is discussed that makes use of electron avalanches in liquid xenon and is currently under development. It is shown that such a radioisotope camera promises many advantages over any other existing gamma-ray cameras. Spatial resolution better than 1 mm and counting rates higher than one million C/sec are possible. An energy resolution of 11% FWHM has recently been achieved with a collimated Hg-203 source using a parallel-plate ionization chamber containing a Frisch grid.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 6
    Publication Date: 2019-06-27
    Description: We report a high-statistics magnetic spectrometer measurement of the geomagnetic cutoff rigidity and related effects at Palestine, Texas. The effective cutoffs we observe are in agreement with computer-calculated cutoffs. We also report measured spectra of albedo and atmospheric secondary particles that come below geomagnetic cutoff.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 78; Apr. 1
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  • 7
    Publication Date: 2019-07-13
    Description: Discussion of techniques currently used in high energy particle astronomy for measuring charged and neutral cosmic rays and their isotope and momentum distribution. Derived from methods developed for accelerator experiments in particle physics, these techniques help perform important particle astronomy experiments pertaining to nuclear cosmic ray and gamma ray research, electron and position probes, and antimatter searches.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Astronomy from a space platform; Symposium; Dec 27, 1971 - Dec 28, 1971; Philadelphia, PA
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  • 8
    Publication Date: 2019-06-27
    Description: Insulated gate field effect transistors using cadmium selenide or telluride as piezoelectric semiconductor material
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA-CR-94541
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  • 9
    Publication Date: 2019-06-27
    Description: A 33-GHz airborne radiometer system has been developed to map large angular scale variations in the temperature of the 3 K cosmic background radiation. A ferrite circulator switches a room-temperature mixer between two antennas pointing 60 deg apart in the sky. In 40 min of observing, the radiometer can measure the anisotropy of the microwave background with an accuracy of plus or minus 1 mK rms, or about 1 part in 3000 of 3 K. The apparatus is flown in a U-2 jet to 20 km altitude where 33-GHz thermal microwave emission from the atmosphere is at a low level. A second radiometer, tuned to 54 GHz near oxygen emission lines, monitors spurious signals from residual atmospheric radiation. The antennas, which have an extremely low side-lobe response of less than -65 dB past 60 deg, reject anisotropic radiation from the earth's surface. Periodic interchange of the antenna positions and reversal of the aircraft's flight direction cancel equipment-based imbalances. The system has been operated successfully in U-2 aircraft flown from NASA-Ames at Moffett Field, Calif.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 49; Apr. 197
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  • 10
    Publication Date: 2019-07-13
    Description: This experiment detected and mapped large-angular-scale anisotropies in the 3 K primordial black-body radiation with a sensitivity of 2x.0001k and an angular resolution of about 10 degs. It measured the motion of the Earth with respect to the distant matter of the Universe (Aether Drift), and probed the homogeneity and isotropy of the Universe (the Cosmological Principle). The experiment used two Dicke radiometers, one at 33 GHz to detect the cosmic anisotropy, and one at 54 GHz to detect anisotropies in the residual oxygen above the detectors. The system was installed in the NASA-Ames Earth Survey Aircraft (U-2), and operated successfully in a series of flights.
    Keywords: SPACE RADIATION
    Type: NASA-CR-158129 , SSL-SER-20-ISSUE-10
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