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  • INSTRUMENTATION AND PHOTOGRAPHY  (6)
  • AIRCRAFT INSTRUMENTATION  (3)
  • 1
    Publication Date: 2011-08-19
    Description: Results on NO2 instruments are reported from the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986. The instruments tested were (1) a two-photon LIF system using a laser for NO2-NO photolysis, (2) a chemiluminescence (CL) detector using FeSO4 for NO2-NO conversion, (3) a CL detector using an arc lamp for NO2-NO photolysis, and (4) a tunable-laser-diode multipath-absorption system. The procedures for the CITE 2 ground-based and flight tests are described in detail, and the results are presented in extensive graphs. Instrument (2) was eliminated because the FeSO4 converted atmospheric PAN to NO, resulting in spuriously high NO2 values. The remaining instruments gave readings in 30-40-percent agreement at NO2 mixing ratios of 100-200 parts per trillion by volume (pptv). At ratios below 50 pptv, the correlation among the measurements was very poor, with a tendency for system (4) to give higher values than (1) or (3).
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10103-10
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  • 2
    Publication Date: 2011-08-19
    Description: NASA has initiated the Global Tropospheric Experiment (GTE) for the study of the chemistry of the global troposphere. One phase of GTE, Chemical Instrumentation Test and Evaluation (CITE), is concerned with the development and validation of measurement techniques for trace species which play important roles in the tropospheric chemical cycles. In connection with CITE 1 an intercomparison of instruments is conducted for the measurement of CO, NO, and OH. These species have been identified as critical for an understanding of homogeneous gas-phase chemistry in the troposphere. The present paper provides an operational overview of the first of three instrument intercomparison field missions conducted as part of GTE/CITE 1. The missions include one ground-based and two airborne missions, and were designed to characterize current capability of measuring ambient levels of CO, NO, and OH.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 12
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  • 3
    Publication Date: 2011-08-18
    Description: Ultrahigh resolution (0.007 per cm) atmospheric solar absorption spectra that have been obtained from a tunable infrared heterodyne radiometer are discussed. The radiometer was developed for ground based observations in the 8-12 micron region, and tunability is achieved through the use of Pb-salt semiconductor laser local oscillators. Spectra have been obtained in a piecewise fashion from 9.1 to 11.1 microns using laser emission modes that exhibit characteristics suitable for local-oscillator operation. Spectra showing absorption features of HNO3, O3, CO2, and H2O are presented along with comparisons of experimental and synthetic spectra calculated using a line-by-line atmospheric transmission model.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Optical Engineering; 21; Mar
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  • 4
    Publication Date: 2011-08-16
    Description: Doppler effect induced small spectral line shifts measured by modified duochromator in MPD arc jet
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: ; ADEMIE DES SCIENCES
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  • 5
    Publication Date: 2011-08-19
    Description: Results are reported on the performance of (1) denuder-tube/chemiluminescent, (2) nylon-filter/ion-chromatography, and (3) tunable-diode-laser/multipath-absorption HNO3 measurement instruments during the NASA Global Tropospheric Experiment Chemical Instrumentation Test and Evaluation 2 (CITE 2) program in summer 1986. The instrument designs, test protocols, and CITE 2 flights are described, and the results are presented in extensive graphs and discussed in detail. The data obtained with the three instruments are shown to be in very poor agreement at mixing ratios below 150 parts per trillion by volume (pptv), with significant discrepancies even at higher levels. Instrument (3) gave systematically higher values than (1) and (2). It is concluded that none of the instruments is accurate enough for reliable use at normal atmospheric HNO3 levels (around 100 pptv).
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 95; 10089-10
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  • 6
    Publication Date: 2011-08-19
    Description: Results from an intercomparison of techniques to measure tropospheric levels of carbon monoxide (CO) are discussed. The intercomparison was conducted as part of the National Aeronautics and Space Administration's Global Tropospheric Experiment (GTE) and was held at Wallops Island, VA, in July 1983. Instruments intercompared included a laser differential absorption method and three grab sample/gas chromatograph methods. The intercomparison consisted of simultaneous measurements of ambient levels of CO and controlled injections of CO from a common manifold. Results from the techniques exhibited a high degree of correlation among themselves and with changes in the CO mixing ratio. The results suggested a level of agreement among the techniques of about 15 percent. However, a day-to-day bias between the techniques was observed, which resulted in differences between techniques as large as 38 percent.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 12
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  • 7
    Publication Date: 2011-08-19
    Description: Results from an intercomparison of techniques to measure tropospheric levels of nitric oxide (NO) are discussed. The intercomparison was part of the National Aeronautics and Space Administration's Global Tropospheric Experiment and was conducted at Wallops Island, VA, in July 1983. Instruments intercompared included a laser-induced fluorescence system and two chemiluminescence instruments. The intercomparisons were performed with ambient air at NO mixing ratios ranging from 10 to 60 pptv and NO-enriched ambient air at mixing ratios from 20 to 170 pptv. All instruments sampled from a common manifold. The techniques exhibited a high degree of correlation among themselves and with changes in the NO mixing ratio. Agreement among the three techniques was placed at approximately + or - 30 percent. Within this level of agreement, no artifacts or species interferences were identified.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 12
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  • 8
    Publication Date: 2011-08-18
    Description: Sachse et al. (1976) have reported the development of an airborne tunable diode laser (TDL) system, named the Differential Absorption CO Monitor (DACOM). The absorption path was 10 m long and located in the free airstream along the fuselage of a C-54 aircraft. The present investigation is concerned with a modification of the DACOM instrument. Differences between the new instrument and the original one are related to a replacement of the external absorption path with a White cell. The instrument has the capability to suppress TDL excess noise. The laser refrigerator has been redesigned to permit an alternative method of cooling the TDL when electric power is not available.
    Keywords: AIRCRAFT INSTRUMENTATION
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  • 9
    Publication Date: 2019-07-13
    Description: A tunable-diode-laser radiometer with a spectral resolution of 0.007/cm was used to obtain IR solar absorption spectra in the 9.1-11.1 micron region. Spectra exhibiting absorption by HNO3, CO2, O3, and H2O were obtained in a piecewise manner using emission modes from a single Pb-salt laser local oscillator. The measured spectra were compared to synthetic atmospheric spectra calculated using a line-by-line model. The results demonstrate that high-resolution IR solar absorption spectroscopy and atmospheric extinction measurements can be routinely performed over wide spectral regions using semiconductor lasers.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Atmospheric transmission; April 21-22, 1981; Washington, DC
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