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  • 1
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    An infrared heterodyne radiometer for high-resolution measurements of solar radiation and atmospheric transmission (1975)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: A tunable, Dicke-switched, infrared heterodyne radiometer (IHR) has been designed, fabricated, tested, and used to observe solar radiation and determine the atmospheric transmissivity in the 9-11-micron spectral band. The IHR provides a spectral resolution of 0.0067 reciprocal cm, a minimum detectable power level of 2.9 times ten to the minus twenty-third power W/Hz, and a temperature resolution of less than 1 K for a source temperature of 1000 K, an IF predetection bandwidth of 100 MHz, and an integration time of 30 s. Detailed design equations and measured IHR performance are presented. The IHR was used to make solar and atmospheric transmission measurements, and a vertical-path atmospheric attenuation of 2.3 dB has been established under favorable weather conditions. The attenuation of solar radiation due to cloud cover and haze has also been investigated.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: IEEE Journal of Quantum Electronics; QE-11; Aug. 197
    Format: text
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  • 2
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    High-sensitivity receiver for infrared laser communications. (1972)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: Description of a high-sensitivity wide-bandwidth 10.6-micron heterodyne receiver for space and ground operational use. The receiver includes a cooled HgCdTe infrared mixer diode, a conical scanner for spatial tracking, an acquisition channel for spatial search and station alignment, and an automatic frequency-control channel to maintain a fixed laser frequency offset. The infrared mixer is designed to provide nearly quantum-noise-limited operation over an extended range of mixer temperature, bias voltage, and intermediate frequency. The resultant experimental receiver has a measured noise equivalent power of less than 10 to the minus 19th W/Hz over the 15- to 40-MHz i.f. band for mixer temperatures from 85 to 115 K, and less than 2 x 10 to the minus 19th W/Hz up to 140 K. Mixer 3-dB cutoff frequencies as high as 420 MHz were measured at a mixer temperature of 125 K. An analysis and engineering equations are given for receiver noise components, noise equivalent power, available mixer conversion gain, mixer transducer gain, and quantum-noise factor in terms of such factors as mixer parameters, quantum efficiency, mixer temperature, dynamic conductance, bias voltage, local oscillator power, and i.f. amplifier characteristics.
    Keywords: COMMUNICATIONS
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Infrared 10.6-micron heterodyne detection with GigaHertz IF capability. (1967)
    In:  Other Sources
    Details
    Publication Date: 2011-08-12
    Description: Heterodyne detection in photoconductors, discussing engineering design for high sensitivity in IR
    Keywords: COMMUNICATIONS
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    NASA TECHNICAL REPORTS
  • 4
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    CO2 laser communication systems for near-earth space applications (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Projections of the growth of earth-sensing systems for the latter half of the 1980's show a data-transmission requirement of 300 Mbit/s and above. The most efficient technique to return the data from a sensing satellite to a ground station is through a geosynchronous data relay satellite. A laser system is most attractive for the space-to-space link. A five-year program was conducted which has shown the basic technical feasibility of accomplishing this link with a CO2 laser system operating at a wavelength near 10 microns. The system uses a mercury-cadmium-telluride infrared mixer cooled to approximately 100 K by a radiative cooler. The laser local oscillator and coupling-modulated laser transmitter use conductively cooled beryllium oxide construction. The optical antenna for transmission and reception has a gain of nominally 92 dB with a 3-dB beamwidth of 80 microrad. Tracking jitter is less than ten microrad, and signal acquisition occurs in less than 1 min. The receiver subsystem has a sensitivity of 10 to the -19th power W/Hz, accommodates a 300-Mbit/s data rate, and can track Doppler frequency variations over a + or - 700-MHz range.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: IEEE; vol. 65
    Format: text
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  • 5
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    Infrared heterodyne receivers with IF responses approaching 5 GHz (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Specialized coherent 10.6 micrometer infrared receivers were developed with infrared frequency responses approaching 5 GHz. Carbon dioxide lasers were employed for these applications because of their availability, stability, and high average power levels. Heterodyne receivers which employ extrinsic photoconductive Ge:Cu(Sb) mixers were developed for measurements of carbon dioxide laser scattering to determine: (1) the drive lower hybrid wave density fluctuations; and (2) the plasma ion temperature of the dense Tokamak plasmas.
    Keywords: LASERS AND MASERS
    Type: NASA. Langley Res. Center Heterodyne Systems and Technol., Pt. 2 p327-340 (SEE N80-29672 20-36)
    Format: application/pdf
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  • 6
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    Application of tunable diode lasers as local oscillators in an Infrared Heterodyne Radiometer (IHR) (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The utility of diode lasers as local oscillators (LOs) in a heterodyne receiver application was investigated. The CW power, spectral tunability, spectral stability, and spatial intensity distribution of the TDL outputs were measured. A tunable diode laser LO was incorporated into a laboratory Dicke-switched infrared heterodyne setup and used to measure radiometer sensitivity as well as spectroscopic characteristics of selected absorption lines of ammonia. The test results on one of the two tunable diode lasers are emphasized in an attempt to provide a comprehensive data package which may be useful for future planning purposes. The second tunable diode laser exhibits characteristics similar to the fully tested TDL with the exception that some changes in its performance characteristics as it was temperature cycled between room temperature and the operating temperature of approximately 50K occurred.
    Keywords: LASERS AND MASERS
    Type: NASA-CR-159121
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 7
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    Spaceborne CO2 laser communications systems (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Projections of the growth of earth-sensing systems for the latter half of the 1980's show a data transmission requirement of 300 Mbps and above. Mission constraints and objectives lead to the conclusion that the most efficient technique to return the data from the sensing satellite to a ground station is through a geosynchronous data relay satellite. Of the two links that are involved (sensing satellite to relay satellite and relay satellite to ground), a laser system is most attractive for the space-to-space link. During 1975 a major step toward the development of CO2 laser systems for space-to-space applications is being completed. This step is the completion of a 300 Mbps data relay receiver and its modification into a transceiver. The technology and state-of-the-art of such systems are described in detail in this paper.
    Keywords: SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING
    Type: EASCON ''75; Electronics and Aerospace Systems Convention; Sep 29, 1975 - Oct 01, 1975; Washington, DC
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Atmospheric temperature profiling using an infrared heterodyne radiometer (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The applicability of a high resolution infrared heterodyne radiometer for atmospheric temperature profiling is considered. Upwelling radiation at the 754.321/cm and the 945.976/cm rotational-vibrational lines of CO2 are monitored by a six IF channel infrared heterodyne radiometer with spectral specificity between 0.002 and 0.012/cm. Computer simulated retrievals have been carried out which indicate a maximum temperature inaccuracy of 3.5 K for vertical profiles between ground level and 50 km and a system integration time of 8 seconds.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Seminar on Modern utilization of infrared technology II: Civilian and military; Aug 26, 1976 - Aug 27, 1976; San Diego, CA
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    NASA TECHNICAL REPORTS
  • 9
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    Infrared heterodyne spectrometer measurements of vertical profile of tropospheric ammonia and ozone (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Remote sensing of the concentration and vertical distribution of atmospheric gases has been carried out using a dual CO2 laser multichannel infrared heterodyne spectrometer (IHS). The high specificity and nearly quantum-noise-limited sensitivity of the IHS provide the capability of scanning individual signature lines of selected atmospheric constituents in the 9 to 11 micron region. A comprehensive investigation of the spectral overlap between CO2 laser local oscillator transitions and selected atmospheric constituents was performed; measurements of the atmospheric absorption of solar radiation from the ground were carried out at selected laser transitions for ammonia and ozone.
    Keywords: ENVIRONMENT POLLUTION
    Type: AIAA PAPER 77-73 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
    Format: text
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  • 10
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    Wideband infrared heterodyne receiver front-end (1974)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: A 10.6 micron infrared heterodyne receiver front end was developed for use in a wideband CO2 laser communications link. The infrared receiver employs an 850 MHz response PV HgCdTe photomixer which is mounted in a space quality housing, a low-noise 5 to 1500 MHz IF preamplifier, and a remote control panel. The receiver was designed to handle + or - 750 MHz of Doppler shift while providing an instantaneous information bandwidth of 400 MHz. The measured receiver sensitivity NEP was 1.0 x 10 to the 19th power W/Hz for a photomixer temperature of T sub m = 77 K and an IF beat frequency of 20 MHz and degraded to 1.75 x 10 to the 19th power W/Hz for T sub m = 130 K.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-139172 , AIL-7886-1
    Format: application/pdf
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