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  • 1
    Publication Date: 2011-08-16
    Description: A simple but useful formula describing the effect of electron gun pulse width on the time of flight (TOF) spectra measured in translational spectroscopy experiments is developed. An approximately monoenergetic pulsed electrostatically focused electron beam traverses a scattering cell filled with a Maxwellian gas. Inelastic electron collisions with the gas produce metastable particles, ions, scattered electrons, and photons which then pass through a collimating slit system at right angles to the electron beam. TOF techniques are used to separate the photon signal from the metastable particle signal and to measure the TOF distribution of the metastable species.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Review of Scientific Instruments; 45; Feb. 197
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  • 2
    Publication Date: 2011-08-16
    Description: The factors determining the sensitivity of a real astronomical heterodyne spectrometer are described. The deviation from the ideal heterodyne system for line detection is described in terms of a series of degradation factors. A discussion of degradation due to a low local oscillator power and to line profile detection is presented. Representative values for the degradation factors are given. Even with a total degradation of not less than 30, the heterodyne spectrometer is still found to be a highly sensitive tool in IR astronomy.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
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  • 3
    Publication Date: 2016-06-07
    Description: The characteristics of infrared molecular emissions induced by energetic collisions between ambient atmospheric species and surfaces in Earth orbit are investigated, using a low-nitrogen-cooled filter wheel photometer covering the wavelength range 0.9-.5 microns with a resolving power Lambda/Delta Lambda of approximately 100. This resolving power is sufficient for identification of the molecular or atomic fluorescent spaces causing the glow.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: NASA. Marshall Space Flight Center 2d Workshop on Spacecraft Glow; p 250-259
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  • 4
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    In:  Other Sources
    Publication Date: 2013-08-29
    Description: As part of NASA's Airborne Astronomy Program, research teams studied the infrared emissions of comet Halley before and after perihelion from NASA's C-141 Kuiper Airborne Observatory (KAO) and from NASA's Lear Jet Observatory (LJO). The objectives were to determine the presence of water vapor and other molecules and the composition of dust in the coma and nucleus. The C-141/KAO, the LJO, the detecting instruments, and the observational flight plans are described. The observed spectral range extended from 2 to 800 microns, plus wide-field, visible photography. The C-141/KAO's flights occurred in December 1985 from California and in March and April 1986 from New Zealand. The LJO's observations were made from Kwajalein Island in April 1986.
    Keywords: ASTROPHYSICS
    Type: ESA, Proceedings of the 20th ESLAB Symposium on the Exploration of Halley's Comet. Volume 3: Posters; p 215-221
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  • 5
    Publication Date: 2011-08-16
    Description: A discussion and an evaluation of the degradation in sensitivity are given for a heterodyne spectrometer employing a HgCdTe photodiode mixer and tunable diode lasers. The minimum detectable source brightness is considered as a function of the mixer parameters, transmission coefficient of the beam splitter, and local oscillator emission powers. The degradation in the minimum detectable line source brightness that results from the bandwidth being a fraction of the line width is evaluated and plotted as a function of the wavelength and bandwidth for various temperature to mass ratios. It is shown that the minimum achievable degradation in the sensitivity of a practical astronomical heterodyne spectrometer is about 30. Estimates of SNRs with which IR line emission from astronomical sources of interest may be detected are given.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 15; Feb. 197
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  • 6
    Publication Date: 2011-08-17
    Description: Infrared heterodyne spectroscopy provides a means of measuring the intensity profiles of individual rotation-vibration spectral lines with high sensitivity. Considerable effort has been expended on optimizing these instruments for remote measurements of gases in planetary atmospheres with the result that present-generation spectrometers are beginning to provide new and startling results on the planets. The fundamental principles of laser heterodyne spectroscopy are discussed. Detailed considerations of the optical design and the electronic design of the spectral-line receiver are given. Representative results obtained with this spectrometer are discussed, including precision frequency measurements of NH3 (nu-2) lines, detection of auroral emission from Jupiter, and measurements of terrestrial O3 and CO2.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering; 17; Jan
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  • 7
    Publication Date: 2011-08-19
    Description: The technique of laser heterodyne spectroscopy has been applied to the measurement of solar oscillations. Coherent mixing of solar radiation with the output of a frequency-stabilized CO2 laser permits the measurement of fully resolved profiles of solar absorption lines with high spectral purity and excellent frequency stability. This technique has been used to measure OH pure rotation lines in the infrared solar spectrum. Power spectra of these line frequency measurements show the well-known 5-min oscillations as well as significant velocity power at shorter periods.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 25; 58-62
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  • 8
    Publication Date: 2011-08-18
    Description: A diode-laser-based, ultrahigh resolution IR heterodyne spectrometer for laboratory and field use has been developed for operation between 7.5 and 8.5 microns. The local oscillator is a PbSe tunable diode laser kept continuously at operating temperatures of 12-60 K using a closed-cycle cooler. The laser output frequency is controlled and stabilized using a high-precision diode current supply, constant temperature controller, and a shock isolator mounted between the refrigerator cold tip and the diode mount. The system largely employs reflecting optics to minimize losses from internal reflection and absorption and to eliminate chromatic effects. Spectral analysis of the diode-laser output between 0 and 1 GHz reveals excess noise at many diode current settings, which limits the IR spectral regions over which useful heterodyne operation can be achieved. Observations have been made of atmospheric N2O, O3, and CH4 between 1170 and 1200/cm, using both a single-frequency swept IF channel and a 64-channel RF spectral line receiver with a total IF coverage of 1600 MHz.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics; 21; Jan. 15
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  • 9
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    In:  Other Sources
    Publication Date: 2011-08-18
    Description: The possibility of detecting IR molecular line emission from cometary parent molecules is explored. Due to the non-LTE conditions in the inner coma and the large amount of near IR solar flux, IR fluorescence will be a significant source of cometary emission and, in fact, will dominate the grain radiation in a sufficiently high resolution instrument. The detection of this line emission will be difficult due to absorption in the terrestrial atmosphere, but it appears possible to measure cometary H2O emission from airplane altitudes. As IR molecular line emission represents one of the few promising methods of detecting cometary parent molecules directly, further research on this problem should be vigorously pursued. Previously announced in STAR as N83-30344
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 276; 782-797
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  • 10
    Publication Date: 2011-08-19
    Description: Formaldehyde scattering strengths have been determined for equilibrium distributions of 100 K, 50 K, 20 K, and for the the non-LTE case of an essentially fully relaxed distribution. Integrated band g factors of 2.89 x 10 to the -4th photons/s per molecule for nu1 and 3.83 x 10 to the -4th for nu 5 are obtained. The results indicate that the most promising regions to search for cometary H2CO are at about 2782/cm, at 2794.5/cm, and at about 2835/cm.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 341; 1045-105
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