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  • 1995-1999
  • 1980-1984  (7)
  • 1980  (7)
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  • 1995-1999
  • 1980-1984  (7)
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  • 1
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    Diode laser infrared heterodyne spectrometer (1980)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Schlagwort(e): LASERS AND MASERS
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 40
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 2
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    Ground based infrared heterodyne spectroscopy (1980)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-19
    Schlagwort(e): INORGANIC AND PHYSICAL CHEMISTRY
    Materialart: NASA, Washington Upper Atmosphere Res. Program; p 38-39
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Optical considerations in infrared heterodyne spectrometer design (1980)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: The optical design considerations for optimization of sensitivity, tunability, and versatility of an infrared heterodyne spectrometer are discussed using the GSFC CO2 laser heterodyne spectrometer optical front end as an example. Problems related to the coherent nature of the laser local oscillator beam (e.g., interference effects at edges of optical elements and at the beam combining beamsplitter) are described and proper beamsplitter design discussed. Optimum matching to the telescope is discussed. The severe effects of large central obscuration on the coherent telescope efficiency are described and steps to partially recover the lost system sensitivity are proposed. Measurements made with the GSFC 48 inch telescope (linear obscuration rate = 0.5) and the KPNO McMathe telescope (no obscuration) are given as examples.
    Schlagwort(e): LASERS AND MASERS
    Materialart: NASA. Langley Res. Center Heterodyne Systems and Technol., Pt. 2; p 365-372
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    RF spectrometers for heterodyne receivers (1980)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: Several types of spectrometers developed for radio astronomy receivers which utilize RF filters, multiple oscillators and mixers, digital autocorrelators and acoustic/optic devices are considered. The RF spectrometer developed at GSFC to provide wide bandwidths (greater than 1 GHz) as well as high resolution (5MHz) is described. The 128 channel filter bank is divided into high and low resolution sections. The high resolution section is tunable by providing a second mixer ahead of the filter bank. This is necessary because infrared receivers which use gas lasers as local oscillators are only tunable to specific laser frequencies. To compensate for astronomical Doppler shifts and molecule frequency differences a second local oscillator and mixer is needed. A diagram of the RF section of the filter bank is shown. The RF spectrometer is shown to be the best means of achieving ultra-wide bandwidths for infrared heterodyne receivers. For high resolution with a large number of channels, the acousto/optical spectrometer is the principle instrument, particularly for balloon or space flight applications.
    Schlagwort(e): LASERS AND MASERS
    Materialart: NASA. Langley Res. Center Heterodyne Systems and Technol., Pt. 2 p373-383 (SEE N80-29672 20-36)
    Format: application/pdf
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  • 5
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    Development and performance of a laser heterodyne spectrometer using tunable semiconductor lasers as local oscillators (1980)
    In:  CASI
    Details
    Publikationsdatum: 2016-06-07
    Beschreibung: A diode laser based IR heterodyne spectrometer for laboratory and field use was developed for high efficiency operation between 7.5 and 8.5 microns. The local oscillator is a PbSSe 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. Single laser modes are selected by a grating placed in the local oscillator beam. The system employs reflecting optics throughout 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 infrared spectral regions over which useful heterodyne operation can be achieved. System performance has been studied by making heterodyne measurements of etalon fringes and several Freon 13 (CF3Cl) absorption lines against a laboratory blackbody source. Preliminary field tests have also been performed using the Sun as a source.
    Schlagwort(e): LASERS AND MASERS
    Materialart: NASA. Langley Res. Center Heterodyne Systems and Technol., Pt. 1 p199-208 (SEE N80-29652 20-36)
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    Vibrationally excited silicon monoxide masers (1980)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: Published data on a select group of SiO maser sources have been analyzed for velocity variations as a function of phase. No apparent correlation was found to a level of about 2 km/s. This places constraints on the location of the maser molecules. Such a correlation should be present at some level. The implications for future high resolution infrared measurements are discussed.
    Schlagwort(e): ASTROPHYSICS
    Materialart: PB81-233744 , Symposium on Interstellar molecules; Aug 06, 1979 - Aug 10, 1979; Mont Tremblant, Quebec; Canada
    Format: text
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  • 7
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    A 10 micron heterodyne receiver for ultra high resolution astronomical spectroscopy (1980)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-07-13
    Beschreibung: An improved CO2 laser heterodyne spectrometer is examined. The present system uses reflective optics to eliminate refocusing at different wavelengths, and the local oscillator is a line-center-stabilized isotopic CO2 laser. A tunable diffraction grating makes possible easy and rapid selection of over 50 transitions per isotope of CO2. The IF (0 to 1.6 GHz) from the HgCdTe photomizer is analyzed by a 128-channel filter bank, consisting of 64 tunable 5-MHz filters and 64 fixed 25-MHz RF filters. These filters provide resolving powers of about 1,000,000 to 10,000,000 and velocity resolution of 50 to 250 m/sec; their output is synchronously detected, integrated, multiplexed and stored in a buffer memory for the desired integration period. Kitt Peak observations show the wide spectral coverage, wide mixer and electronics bandwidth, and high sensitivity of the system.
    Schlagwort(e): INSTRUMENTATION AND PHOTOGRAPHY
    Materialart: Symposium on Interstellar molecules; Aug 06, 1979 - Aug 10, 1979; Mont Tremblant, Quebec; Canada
    Format: text
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