SEARCH · Search NASA

Results for “Line Positions”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8

All sources NASA NTRS DOE OSTI

NASA NTRS1979

Numerical simulation of VTPR temperature retrievals in a severe storm environment

Environmental conditions prior to convective development on the Great Plains of the U.S. on one case study day were investigated using the high-resolution infrared radiation sounder (HIRS) on Nimbus 6. A dual-retrieval scheme was developed to retrieve both lower tropospheric moisture and temperature parameters from the HIRS radiances. Total precipitable water, surface dew point temperatures, and stability indices were analyzed at a resolution of up to 30 Km on this day. Correlations with interpolated NES rawinsonde values were high and intrinsic noise levels were low. The true quality of the mesoscale analyses, however, is only seen by examining the small scale features at a scale of approximately 100 Km. Perturbations on the dry line feature for this day were seen in the satellite data, although the dry line position was just as easily picked up by surface observations. Convective development 2 1/2 hours later did seem to correlate well with the local maxima of moisture and instability seen in the satellite analyses.

Vonderhaar, T. H.↗

NASA NTRS1980

Dual mode actuator

Compact mechanism functions under automatic control, manual control, or both. Output shaft rotation is controlled automatically by two hydraulic cylinders or manually by movement of input lever. Automatic control movement is isolated from manual-control movement by adjustment of force on piston spring. Actuator can be modified to control straight line position rather than rotation, or to open valves that regulate fluid flow in actuator, thus creating special movements other than simple rotation.

Rick, S. C.↗

NASA NTRS1979

High-resolution spectral measurement of the HNO3 5.9-micron band using a tunable diode laser

High resolution spectra in the region of the v(2) band of nitric acid have been obtained for selected portions of the HNO3 spectrum using tunable diode laser techniques. Continuous spectra are presented from 1718.97/cm to 1729.57/cm, with a spectral resolution not greater than 0.001/cm (30 MHz). Absolute line intensities and line positions are presented. Self- and foreign-gas (N2) broadening coefficients were iteratively calculated from the experimental data and were determined to be alpha(a) = 0.74/cm atm and alpha (f) = 0.13/cm atm, respectively.

Bair, C. H.↗

NASA NTRS1980

Photodissociation of isotopically heavy O2 as a source of atmospheric O3

(O-18)(O-16) is the sixth most abundant gas in the atmosphere after (N-14)(N-14), (O-16)(O-16), Ar, (N-15)(N-14) and H2O. From available data on line positions in the Schumann-Runge (S-R) bands (175 to 205 nm) of (O-18)(O-16) its atmospheric photodissociation rates are estimated. In the high stratosphere and mesosphere this proposed source of O and O3 could be significant compared to photodissociation of (O-16)(O-16) although the estimates are subject to several uncertainties that are discussed. The transmission of solar radiation is calculated through the S-R bands of (O-18)(O-16) and (O-16)(O-16) with transmission functions averaged over individual S-R bands.

Cicerone, R. J.↗

NASA NTRS1983

Coherent anti-Stokes Raman spectroscopic modeling for combustion diagnostics

The status of modelling the coherent anti-Stokes Raman spectroscopy (CARS) spectra of molecules important in combustion, such as N2, H2O, and CO2, is reviewed. It is shown that accurate modelling generally requires highly precise knowledge of line positions and reasonable estimates of Raman linewidths, and the sources of these data are discussed. CARS technique and theory is reviewed, and the status of modelling the phenomenon of collisional narrowing at pressures well above atmospheric for N2, H2O, and CO2 is described. It is shown that good agreement with experiment can be achieved using either the Gordon rotational diffusion model or phenomenological models for inelastic energy transfer rates.

Hall, R. J.↗

NASA NTRS1983

AFGL atmospheric absorption line parameters compilation - 1982 edition

The latest edition of the AFGL atmospheric absorption line parameters compilation for the seven most active infrared terrestrial absorbers is described. Major modifications to the atlas for this edition include updating of water-vapor parameters from 0 to 4300 per cm, improvements to line positions for carbon dioxide, substantial modifications to the ozone bands in the middle to far infrared, and improvements to the 7- and 2.3-micron bands of methane. The atlas now contains about 181,000 rotation and vibration-rotation transitions between 0 and 17,900 per cm. The sources of the absorption parameters are summarized.

Rothman, L. S.↗

NASA NTRS1984

The v = 0 - 0 spectrum of H2

Ground-state rotational parameters for molecular hydrogen are evaluated using a combination of laboratory and observational data. High-accuracy v = 0 - 0 S(0)-S(5) frequencies from infrared laboratory measurements are analyzed simultaneously with available observed frequencies for the S(8), S(9), S(12), S(13), S(14), and S(15) Orion emission lines. The laboratory and Orion measurements are consistent with each other within their measurement errors. The combined data set yields a determination of five v = 0 rotational parameters and an improvement in the high-J calculated line positions. The analysis produces the parameters (in per cm): B(0) = 59.334627(30), D(0) = 0.0456912(30), H(0) = 4.8974(90) x 10 to the -5th, L(0) = -6.320(110) x 10 to the -8th, M(0) = 7.19(30) x 10 to the -11th, where a correction is made for the estimated contribution of sixth and higher orders.

Jennings, D. E.↗

NASA NTRS1985

Comparison of the frequencies of NH3, CO2, H2O, N2O, CO, and CH4 as infrared calibration standards

The absolute accuracies of infrared calibration standards for the line positions have been investigated using a 0.0056-kayser-resolution (unapodized) Fourier-transform spectrum recorded from 550 to 5000 kayser. The spectrum has been obtained using a multicell arrangement containing the various molecular species. Detailed comoparisons reveal that standards for CO2, CH4, and N2O obtained from laser research and NH3 from Fourier-transform spectrometer research are consistent within the accuracies of the present data (+ or 0.0001 kayser). However, certain N2O, H2O, and CO values in the 1100-to 2300 kayser region are systematically high by 0.0001 to 0.0004 kayser. Correction factors for the H2O and CO standards are obtained to bring these into agreement with the laser values. In addition, corrected values for the 2nu-2 and nu-1 bands of N2O at 9 microns are reported.

Brown, L. R.↗

NASA NTRS1986

A lateral guidance algorithm to reduce the post-aerobraking burn requirements for a lift-modulated orbital transfer vehicle

A lateral guidance algorithm which controls the location of the line of intersection between the actual and desired orbital planes (the hinge line) is developed for the aerobraking phase of a lift-modulated orbital transfer vehicle. The on-board targeting algorithm associated with this lateral guidance algorithm is simple and concise which is very desirable since computation time and space are limited on an on-board flight computer. A variational equation which describes the movement of the hinge line is derived. Simple relationships between the plane error, the desired hinge line position, the position out-of-plane error, and the velocity out-of-plane error are found. A computer simulation is developed to test the lateral guidance algorithm for a variety of operating conditions. The algorithm does reduce the total burn magnitude needed to achieve the desired orbit by allowing the plane correction and perigee-raising burn to be combined in a single maneuver. The algorithm performs well under vacuum perigee dispersions, pot-hole density disturbance, and thick atmospheres. The results for many different operating conditions are presented.

Herman, G. C.↗

NASA NTRS1988

Response function of a tunable diode laser spectrometer from an iterative deconvolution procedure

A deconvolution procedure commonly used for resolution enhancement of spectra has been applied to the determination of the response function of a tunable diode laser spectrometer. The method is sufficiently fast and simple for routine application when correcting for nonnegligible instrumental broadening. Absolute linestrengths of CH4 in the 1327/cm region and line positions of HNO3 in the 1335/cm region, measured with the aid of the deconvolution technique, are reported here.

May, Randy D.↗

NASA NTRS1988

Spectra of van der Waals complexes (dimers) with applications to planetary atmospheres

Spectral features observed in the atmosphere of Titan by the Voyager IR experiment have been attributed to weakly bound complexes of N2 and H2, dominant and minor constituents, respectively. The abundance of H2-N2 dimers there was computed. Current calculations include quantitative spectral line positions and intensities for N2-Ar and CO2-CO2 relating to Titan and Earth, and to Mars and Venus, respectively. This work suggests applications to spectra of planetary atmospheres obtained in spacecraft missions.

Fox, Kenneth↗

NASA NTRS1989

Computer processing of tunable diode laser spectra

A computer-controlled tunable diode laser spectrometer and spectral analysis software are described. The three-channel system records simultaneously the transmission of a subject gas, a temperature-stabilized etalon, and a calibration gas. The software routines are applied to diode laser spectra of HNO3 and NO2 to illustrate the procedures adopted for conversion of raw spectral data to useful transmission and harmonic spectra. Extraction of line positions, absorption intensities, collisional broadening coefficients, and gas concentrations from recorded spectra is also described.

May, Randy D.↗

NASA NTRS1990

Density dependence of the 5 micron infrared spectrum of NH3

Measurements of dilute mixtures of NH3 in H2 were made in the window region 1900-2100/cm of the NH3 spectrum to determine is behavior with increasing pressure of H2. The spectra of pure H2, pure NH3, and mixtures of the two, in the total pressure range from 2.38 to 8.17 atm at 309 K, were obtained with a 975-cm white-cell. Synthetic spectra were calculated using precise line strengths, line positions, and a Lorentz profile. The experimental and calculated spectra are in reasonably good agreement, except that the former is super-imposed on a rather flat background not given by the calculation. A possible mechanism for this background is suggested.

Chapados, Camille↗

NASA NTRS1989

Influence of temperature on the infrared spectrum of the coronene molecule

Laboratory experiments were performed to study the temperature dependence of the absorption spectrum of the coronene molecule (C24H12), believed to be representative of the polycyclic aromatic hydrocarbon (PAH) molecules present in the interstellar medium. The main results is that both line positions and total intensities are almost unchanged when varying the temperature so that the spectrum is mostly temperature independent in the explored range, supporting the modeling of the IR emission originally made by Leger and Puget where room temperature was used in the calculations. In the structure of the band shape, small temperature correlated changes are observed. Qualitative arguments are given to interpret them.

Bernard, Jean-Phillipe↗

NASA NTRS1991

Advanced infrared astronomy

This task supports the application of infrared heterodyne spectroscopy and other high resolution techniques, as well as infrared arrays to ultra-high resolution studies of molecular constituents of planetary atmospheres. High spectral and spatial resolution measurement and analysis of individual spectral lines permits the retrieval of distributions of atmospheric molecular abundances and temperatures and thus, information on local photochemical processes. Determination of absolute line positions to better than 10(exp -8) permits direct measurement of gas velocities to a few m/sec and thus, the study of dynamics. Observations are made from ground based observatories.

Kostiuk, Theodor↗

NASA NTRS1990

Quantitative infrared spectroscopy of minor constituents of the Earth's atmosphere

We obtain quantitative laboratory spectroscopic measurements of molecular constituents which are of importance in understanding the health of the Earth's atmosphere, and, in particular, emphasize those species which are important for understanding stratospheric kinetics or are used for long term monitoring of the stratosphere. Our measurements provide: (1) line and band intensity values which are needed to establish limits of detectability for as yet unobserved species and to quantify the abundance of those species which are observed; (2) line-positions, -half widths and pressure induced shifts are all needed for remote sensing techniques, and (3) data on the above basic molecular parameters at temperatures and pressures appropriate for the real atmosphere.

Chackerian, C., Jr.↗

NASA NTRS1990

Tunable far infrared studies of molecular parameters in support of stratospheric measurements

The purpose of this research is to make precise, fully line-resolved measurements of molecular parameters that are necessary for the analysis of spectra obtained in far infrared field measurement programs. These measurements make it possible to accurately analyze the data from field measurements to obtain atmospheric concentration profiles of key trace gases involved in the ozone chemistry. The research objectives include: measurements of pressure broadening of molecular lines of OH, O2, O3, HCl, and H2O, their temperature dependence, and, when possible, the pressure-induced frequency shifts of the lines; measurements of line positions of radical species, such as HO2.

Chance, K. V.↗

NASA NTRS1991

Improved spectroscopic line parameters for the ozone molecule

Recently the authors made a comprehensive compilation of improved line positions, intensities, and lower state energies of ozone between 0 and 3400/cm. Examples of improvement brought by these data and progress achieved in remote sensing using them are given. Areas for future study include hot bands in the higher wavenumber range, spectral regions above 3400/cm, the O-17 isotopic variants of ozone, broadening coefficients, and emission from high-lying vibrational levels of ozone in the upper atmosphere.

Flaud, J. M.↗