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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
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NASA NTRS1988

Spectroscopic planetary detection

One of the most promising methods for the detection of extra-solar planets is the spectroscopic method, where a small Doppler shift (approximately 10 meters/sec) in the spectrum of the parent star reveals the presence of planetary companions. However, solar-type stars may show spurious Doppler shifts due to surface activity. If these effects are periodic, as is the solar activity cycle, then they may masquerade as planetary companions. The goal of this investigation is to determine whether the solar cycle affects the Doppler stability of integrated sunlight. Observations of integrated sunlight are made in the near infrared (approximately 2 micrometer), using the Kitt Peak McMath Fourier transform spectrometer, with an N2O gas absorption cell for calibration. Researchers currently achieve an accuracy of approximately 5 meters/sec. Solar rotation velocities vary by plus or minus 2000 meters/sec across the solar disk, and imperfect optical integration of these velocities is the principal source of error. We have been monitoring the apparent velocity of integrated sunlight since 1983. They initially saw a decrease of approximately 30 meters/sec in the integrated light velocity from 1983 through 1985, but in 1987 to 1988 the integrated light velocity returned to its 1983 level. It is too early to say whether these changes are solar-cycle related. Although the FTS, unlike a slit spectrograph, has a large field of view, researchers are always looking for ways to improve the optical integration of the solar disk. They recently made an improvement in the method used to optically collimate the FTS, and this has reduced the error level, eliminating some systematic effects seen earlier.

Deming, Drake↗
NASA NTRS1988

The ratio of solid to gas phase CO in the line of sight to W33A

Spectroscopic observations of the IR source W33A, obtained in the M band (4.6 microns) at resolution 0.057/cm using the Fourier-transform spectrometer at the Cassegrain focus of the Canada-France-Hawaii Telescope on July 12-13, 1987, are reported. The spectrum is shown, and equivalent widths and CO column densities are presented in tables. The absorption lines detected indicate the presence of gas at both 23 and 120 K, attributed to the molecular-cloud core and gas near the source, respectively, but very little solid-phase CO.

Mitchell, George F.↗
NASA NTRS1988

Measured line positions and strengths of methane between 5500 and 6180/cm

Calculations for the positions and strengths of over 2000 methane absorption lines stronger than 0.0001/sq cm per atm have been obtained in the 5500-6180/cm spectral region. Spectra were obtained at room temperature using the Fourier transform spectrometer at the Kitt Peak National Observatory solar telescope. The 2nu3 band strength of C-12H4 was shown to be 1.641/sq cm per atm. A Herman-Wallis-type correction of 1 + 0.0298 m + 0.000536 sq m was also found.

Margolis, Jack S.↗
NASA NTRS1988

Accurate energy levels for singly ionized platinum (Pt II)

New observations of the spectrum of Pt II have been made with hollow-cathode lamps. The region from 1032 to 4101 A was observed photographically with a 10.7-m normal-incidence spectrograph. The region from 2245 to 5223 A was observed with a Fourier-transform spectrometer. Wavelength measurements were made for 558 lines. The uncertainties vary from 0.0005 to 0.004 A. From these measurements and three parity-forbidden transitions in the infrared, accurate values were determined for 28 even and 72 odd energy levels of Pt II.

Reader, Joseph↗
NASA NTRS1988

Passive tilt compensation in an FTS using a double-sided flat retroflector

An optical configuration for a tilt-compensated Fourier transform spectrometer is presented. An expanded and collimated He-Ne laser beam was passed through the interferometer and the collimated output was observed visually. The double-sided mirror was tilted through angles approaching 1 deg with no apparent degradation in the interference quality.

Jennings, Donald E.↗
NASA NTRS1988

Polarization of microwave noise source radiation in the 30 GHz to 300 GHz range

Radiation spectra have been obtained in order to calculate the frequency bandwidth and polarization of three microwave noise sources. Results were obtained in the 1-10-mm wavelength region using a lamellar grating Fourier transform spectrometer and a helium-cooled bolometer detector. A secondary transmission region was found to have an input current as well as a polarization dependence, despite the directional output of the waveguide antenna.

Poutous, M. K.↗
NASA NTRS1988

High resolution, balloon-borne emission spectroscopy of trace species in the lower stratosphere - N2O5, HNO3

A liquid-nitrogen cooled Fourier transform spectrometer (SIRIS) measures thermal limb-emission of the stratosphere from a balloon platform at a nominal altitude of 40 km, under night and day conditions, with a 3 km vertical resolution. N2O5 and HNO3 mixing ratios inferred from emission spectra are compared with previous measurements and with the predictions from a one-dimensional photochemical model.

Brasunas, J.↗
NASA NTRS1989

Infrared line intensity measurements in the v = 0-1 band of the ClO radical

Integrated line intensity measurements in the ClO-radical fundamental vibrational v = 0-1 band were carried out using a high-resolution Fourier transform spectrometer coupled to a long-path-length absorption cell. The results of a series of measurements designed to minimize systematic errors, yielded a value of the fundamental IR band intensity of the ClO-radical equal to 9.68 + or - 1.45/sq cm per atm at 296 K. This result is consistent with all the earlier published results, with the exception of measurements reported by Kostiuk et al. (1986) and Lang et al. (1988).

Burkholder, James B.↗
NASA NTRS1989

Line mixing effects in solar occultation spectra of the lower stratosphere - Measurements and comparisons with calculations for the 1932/cm CO2 Q branch

Line mixing effects have been observed in a CO2 Q branch recorded in 0.01/cm-resolution IR solar occultation spectra of the lower stratosphere. The spectral data were obtained by the Atmospheric Trace Molecule Spectroscopy Fourier transform spectrometer during the Spacelab 3 mission in the spring of 1985. Analysis of the 1932.47/cm Q branch of (C-12)(O-16)2 shows absorption coefficients below the band origin about 0.62 times those calculated using a standard Voigt line-shape function. Calculations of line mixing using the Lorentz halfwidths of the lines and a simple energy-gap scaling law to parameterize rotational energy transfer reproduce the observed absorption coefficients to about 10 percent. The present results provide the first quantitative information on air-broadened line mixing effects in a Q branch at low temperatures (about 210 K) and show that these effects are significant even at the low pressures of the lower stratosphere (about 100 mbar).

Rinsland, Curtis P.↗
NASA NTRS1989

Measurements of argon broadened Lorentz width and pressure-induced line shift coefficients in the nu4 band of (C-12)H4

Room temperature argon broadened halfwidth and pressure-induced line shift coefficients have been determined for 118 transitions in the nu4 band of (C-12)H4 from analysis of high resolution laboratory absorption spectra recorded with the McMath Fourier transform spectrometer operated on Kitt Peak by the National Solar Observatory. Transitions up to J-double-prime = 12 have been measured using a nonlinear least-squares spectral fitting procedure. The variation of the measured halfwidth coefficients with symmetry type and rotational quantum number is very similar to that measured previously for N2 and air broadening, but the absolute values of the argon broadening coefficients are all smaller. On average, the ratio of the argon broadened halfwidth coefficient to the corresponding N2 broadened halfwidth coefficient is 0.877 + or - 0.017 (2 Sigma). More than 95 percent of the pressure-induced shifts are negative with values ranging from -0.0081 to +0.0055/cm atm. The pressure shifts in argon are nearly equal to corresponding values measured previously in N2 and air.

Rinsland, Curtis P.↗
NASA NTRS1989

Stratospheric HBr mixing ratio obtained from far infrared emission spectra

Emission features of HBr isotopes have been identified in high-resolution FIR emission spectra obtained with a balloon-borne Fourier-transform spectrometer in the spring of 1979 at 32 deg N latitude. When six single-scan spectra at a zenith angle of 93.2 deg were averaged, two features of HBr isotopes at 50.054 and 50.069/cm were obtained with a signal-to-noise ratio of 2.5. The volume mixing ratio retrieved from the average spectrum is 2.0 x 10 to the -11th, which is assumed to be constant above 28 km, with an uncertainty of 35 percent. This stratospheric amount of HBr is about the same as the current level of tropospheric organic bromine compounds, 25 pptv. Thus HBr could be the major stratospheric bromine species.

Park, J. H.↗
NASA NTRS1989

The mixing ratio of the stratospheric hydroxyl radical from far infrared emission measurements

Far infrared emission spectra of the stratosphere, measured with a 0.0033/cm resolution Fourier transform spectrometer using a limb scanning method, are analyzed in order to retrieve the vertical distribution of the hydroxyl radical (OH). The observations cover a time interval between 1300 and 2300 hours, showing a pronounced time decrease of the OH signals. Vertical profiles are obtained for the afternoon and sunset periods. An upper limit is derived from the small signals present in the night measurements. Three different methods of analysis have been applied to the same data set, and the results provided the basis for a critical discussion of the error sources. The results are compared with theoretical predictions and with the results of other experiments.

Carli, Bruno↗
NASA NTRS1989

Measurement of stratospheric HOCl - Concentration profiles, including diurnal variation

Determinations have been made of concentration profiles of HOCl in the earth's stratosphere, including the diurnal variation. Measurements of the rotational Q2 branch at 99.5/cm and of five RR(J3) transitions between 143 and 159/cm were made using far-infrared thermal emission spectroscopy. The spectra were obtained during a balloon flight of the FIRS 2 far-infrared Fourier-transform spectrometer and telescope from Palestine, Texas on May 12-13, 1988. From these measurements, altitude profiles of HOCl from 23 to 42 km are obtained. Daytime and nighttime average profiles of HOCl, as well as measurements on a 30-min time scale through the sunset transition at a single (35 km) altitude are presented. The measured profiles are lower than the current predictions from several modeling groups by a factor of approximately 0.6.

Chance, K. V.↗
NASA NTRS1989

Linestrengths of the nu(2) and nu(4) bands of (C-12)H4 and (C-13)H4

Absorption spectra recorded on the high-resolution Fourier transform spectrometer at Kitt Peak National Observatory/National Solar Observatory were used to measure individual line strengths of the nu(2) and nu(4) bands of (C-12)H4 and (C-13)H4. The measurements were used to obtain expressions that could be used to correctly predict individual line strengths through five orders of magnitude of absorption strength and high values of J-prime. Transition strengths were modeled using the dyad formalism of two interacting bands and a seven-term second-order dipole-moment expansion. The successful fitting of these data indicates that the method can be used to model measurements of 2- to 5-percent precision even at high values of J. For remote sensing applications, the present prediction of the dyad spectrum represents a substantial improvement.

Brown, L. R.↗
NASA NTRS1989

Airborne measurements of stratospheric constituents over Antarctica in the austral spring 1987. I - Method and ozone observations

A Fourier transform spectrometer was flown aboard a DC-8 on 10 flights over Antarctica during August and September, 1987, as part of the Airborne Antarctic Ozone Experiment (AAOE). Observing the sun at infrared wavelengths, it was possible to determine the integrated column amount above the flight altitude for ozone and a number of other chemical species that are believed to be important in the perturbed chemistry of the 'ozone hole'. The paper describes the method, the observations, the data analysis procedure, and the ozone results. During the observation period, ozone developed a steep gradient near the edge of the polar vortex; deep within the vortex, the average ozone column decreased by about 1.6 percent per day during September.

Mankin, William G.↗
NASA NTRS1989

Ground-based infrared measurements of tropospheric source gases over Antarctica during the 1986 austral spring

Simultaneous measurements of the atmospheric burdens of CH4, N2O, CO2, CF2Cl2, and CO above McMurdo Station, Antarctica, have been derived from solar absorption spectra obtained by the Jet Propulsion Laboratory high-resolution Fourier transform spectrometer. In all cases the burdens are smaller than midlatitude values. Furthermore, retrievals of N2O and CH4 indicate that the tropospheric mixing ratios were normal and that the depletion of the burdens can best be accounted for by a downward shift of the volume mixing ratio profiles by some 6-8 km. This rules out the possibility of large-scale upwelling of ozone-poor tropospheric air into the stratosphere being the cause of the Antarctic springtime ozone depletion.

Toon, G. C.↗
NASA NTRS1990

Laboratory studies, analysis, and interpretation of the spectra of hydrocarbons present in planetary atmospheres including cyanoacetylene, acetylene, propane, and ethane

Combining broadband Fourier transform spectrometers (FTS) from the McMath facility at NSO and from NRC in Ottawa and narrow band TDL data from the laboratories with computational physics techniques has produced a broad range of results for the study of planetary atmospheres. Motivation for the effort flows from the Voyager/IRIS observations and the needs of Voyager analysis for laboratory results. In addition, anticipation of the Cassini mission adds incentive to pursue studies of observed and potentially observable constituents of planetary atmospheres. Current studies include cyanoacetylene, acetylene, propane, and ethane. Particular attention is devoted to cyanoacetylen (H3CN) which is observed in the atmosphere of Titan. The results of a high resolution infrared laboratory study of the line positions of the 663, 449, and 22.5/cm fundamental bands are presented. Line position, reproducible to better than 5 MHz for the first two bands, are available for infrared astrophysical searches. Intensity and broadening studies are in progress. Acetylene is a nearly ubiquitous atmospheric constituent of the outer planets and Titan due to the nature of methane photochemistry. Results of ambient temperature absolute intensity measurements are presented for the fundamental and two two-quantum hotband in the 730/cm region. Low temperature hotband intensity and linewidth measurements are planned.

Blass, William E.↗
NASA NTRS1990

Description of SAFIRE for ISES

The SAFIRE (Spectroscopy of the Atmosphere using Far Infrared Emission) is a limb emission experiment using a far-IR Fourier transform spectrometer (FTS) and a mid-IR broadband multispectral radiometer covering the range 80 to 1600/cm. The purpose of this experiment is to obtain vertical distributions of temperature and key constituents of O(y), HO(y), NO(y), ClO(y), and BrO(y) families in the stratosphere, mesosphere, and thermosphere. The spectral channels and gases within each channel are summarized. The instrument includes a 48 element (6 x 8) Ge:GA detector array operating at 4 K in the far-IR and a 105 element (7 x 15) HgCdTe array operating at 80 K in the mid-IR. The SAFIRE uses four different scan modes for vertical coverage and resolution to address various scientific requirements. The SAFIRE data reduction will start with the retrieval of temperature profile as a function of pressure using two CO2 channel data. Constituent distributions then are obtained from other channel data using the retrieved temperature profile. The SAFIRE measurements are limited to the region above the tropopause because of radiance saturation by H2O and clouds. The computational capability necessary to process at the instrument data rate is estimated to be 19 MFLOPS for FTS data and 0.02 MFLOPS for radiometer data. It seems, therefore, that the real-time applications of SAFIRE data using an onboard processing device is not feasible. Although a temperature anomaly may be detected from the two CO2 radiometer channels using an onboard processor for the stratosphere, it is not possible to distinguish between CO2 outflux and temperature anomaly. Temperature anomaly does not, therefore, offer tropospheric information useful for real-time application.

Park, Jae H.↗