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At least 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

A line parameter list for the nu2 and nu4 bands of /C-12/H4 and /C-13/H4, extended to J-prime = 25 and its application to planetary atmospheres

Line parameters (transition frequencies, line strengths, line widths, ground state energies and quantum identifications) for the nu2 and nu4 bands of (C-12)H4 and (C-13)H4 have been calculated for J-prime equal to or less than 25 using the simultaneous coupled fitting procedure of Gray and Robiette. Molecular constants for the nu2 band of (C-13)H4 were estimated from isotopic shifts from (C-12)H4 values. Agreement with laboratory spectra, where available, is always well within 1 kayser over the entire spectral range covered by the list. The most serious problem in comparison with laboratory data is the omission of lines belonging to 'hot' bands in this spectral region. This list is valuable in remote sensing problems for sorting out lines of trace species from weak methane lines and for determining the atmospheric opacity in relatively transparent spectral regions. Applications of the parameter list are demonstrated for remote sounding of the Jovian atmosphere.

Orton, G. S.↗
NASA NTRS1979

The 2.2 GHz Surface Acoustic Wave (SAW) oscillator development Ku-band frequency source development

Two 2.2 GHz SAW oscillators using aluminum nitride on sapphire (AlN/Al2O3) delay lines were fabricated. The oscillators were electronically temperature compensated and characterized. One of the oscillators was used as the frequency reference for the Ku band source; the second oscillator is available for continued evaluation. A 15 GHz frequency source was designed and fabricated. The 15 GHz source consists of a Ku band FET oscillator which is phase locked to the frequency multiplied (X7) output of the 2.2 GHz SAW reference source. The Ku band source was built using microstrip circuit designs, which are hybrid compatible. Two wafer runs of 2.2 GHz TED devices were fabricated and evaluated. The devices were mounted on microstrip test substrates and evaluated as 15 GHz divide by 7 circuits. The device evaluation indicated that in their present form the TED is not a practical circuit element.

Source record↗
NASA NTRS1981

Forced shelf circulation by an alongshore wind band

The forced circulation over a continental shelf generated by the alongshore wind stress is studied within the frictional regime. The model alongshore wind stress has a finite extent in the alongshore direction and oscillates monochromatically, resembling a series of anticyclones traveling across the coastline. Both the shelf-wave response and the localized non-wavelike response exist within the wind band. The numerical results show that the interaction of shelf waves with locally wind-forced response generates a large increase in the phase speed within the wind band. Given an alongshore variation in the alongshore wind stress, a right-bounded phase propagation is possible even in the absence of continental shelf waves. Given a reasonable friction currently accepted for the east coast of the United States, the resonance mechanism at the cutoff frequency may not be important, and lower frequency wind events generate larger amplitude continental shelf circulation. By reducing the friction, energy at cutoff fequencies leaks out of the wind band in both directions effectively. It also is shown that non-wavelike response depends only on the local wind stress and is not affected significantly by friction.

Chao, S.-Y.↗
NASA NTRS1982

Dayglow emissions of the O2 Herzberg bands and the Rayleigh backscattered spectrum of the earth

It is pointed out that numerous fluorescent emissions from the Herzberg bands of molecular oxygen lie in the spectral region 242-300 nm. This coincides with the wavelength range used by orbiting spectrometers that observe the Rayleigh backscattered spectrum of the earth for the purpose of monitoring the vertical distribution of stratospheric ozone. Model calculations suggest that Herzberg band emissions in the dayglow could provide significant contamination of the ozone measurements if the quenching rate of O2(A3Sigma) is sufficiently small. It is noted that this is especially true near 255 nm, where the most intense fluorescent emissions relative to the Rayleigh scattered signal are located and where past satellite measurements have shown a persistent excess radiance above that expected for a pure ozone absorbing and molecular scattering atmosphere. Very small quenching rates, however, are adequate to reduce the dayglow emission to negligible levels. Noting that available laboratory data have not definitely established the quenching on the rate of O2(A3Sigma) as a function of vibration level, it is emphasized that such information is required before the Herzberg band contributions can be evaluated with confidence.

Frederick, J. E.↗
NASA NTRS1983

Absolute band strengths of halocarbons F-11 and F-12 in the 8- to 16-micron region

The infrared strengths of three vibrational band systems of halocarbon F-11 and four vibrational band systems of halocarbon F-12 in the 'atmospheric window' between 8 and 16 microns were measured at 296 + or - 1 K using a Fourier transform infrared spectrometer. These results were obtained at a maximum instrumental resolution of 0.06/cm. The measurements of the total infrared band strengths for F-11 and F-12 would indicate approximately 17% and 5% greater absorbance, respectively, than those strengths used in recent greenhouse warming calculations by Ramanathan (1975), Wang et al. (1976), and Lacis et al. (1981), and consequently, a corresponding increase in the possible atmospheric warming effect by these halocarbons.

Kagann, R. H.↗
NASA NTRS1983

The C2H, C2, and CN electronic absorption bands in the carbon star HD 19557

Infrared spectrophotometry of the R-type carbon star HD 19557 is presented. Two unusual spectroscopic features are seen: a 3.1 micron band is lacking and a 2.8 micron band is present. Identifications are proposed for three previously unreported stellar absorption bands with electronic sequences of C2, CN, and C2H. The latter is proposed to be responsible for the 2.8 micron feature. The atmospheric structure of the star is studied with synthetic spectra, and an effective temperature between 2600 K and 3000 K is suggested. No SiC emission is seen at 11.3 microns, indicating that grain formation is not a viable process around the star. The lack of dust in R stars may suggest a salient difference between R and N types.

Goebel, J. H.↗
NASA NTRS1983

CO 1-0 band isotopic lines as intensity standards

Fundamental band vibration-rotational line intensities are reported for the (C-12)(O-16), (C-13)(O-16), and (C-12)(O-18) molecules. The intensities were computed using numerically obtained matrix elements of a recently, determined electric dipole moment function. New intensity measurements for some of these lines obtained via high-resolution Fourier spectra are also reported. The overall consistency (approximately 2.2 percent) between calculations, which are based on recent experimental determinations of CO 1-0 band intensities, not including our own, those of the authors, and independent experimental results of the authors suggests that the lines of the fundamental band of CO can be used as absolute intensity standards.

Chackerian, C., Jr.↗
NASA NTRS1983

A user's manual for the NASA/JPL synthetic aperture radar and the NASA/JPL L and C band scatterometers

Airborne synthetic aperture radars and scatterometers are operated with the goals of acquiring data to support shuttle imaging radars and support ongoing basic active microwave remote sensing research. The aircraft synthetic aperture radar is an L-band system at the 25-cm wavelength and normally operates on the CV-990 research aircraft. This radar system will be upgraded to operate at both the L-band and C-band. The aircraft scatterometers are two independent radar systems that operate at 6.3-cm and 18.8-cm wavelengths. They are normally flown on the C-130 research aircraft. These radars will be operated on 10 data flights each year to provide data to NASA-approved users. Data flights will be devoted to Shuttle Imaging Radar-B (SIR-B) underflights. Standard data products for the synthetic aperture radars include both optical and digital images. Standard data products for the scatterometers include computer compatible tapes with listings of radar cross sections (sigma-nought) versus angle of incidence. An overview of these radars and their operational procedures is provided by this user's manual.

Thompson, T. W.↗
NASA NTRS1984

LANDSAT 4 band 6 data evaluation

Previously experienced data collection problems were successfully resolved. A limited effort, directed at improved methods of display of TM Band 6 data, has concentrated on implementation of intensity hue and saturation displays using the Band 6 data to control hue. These displays tend to give the appearance of high resolution thermal data and make whole scene thermal interpretation easier by color coding thermal data in a manner that aids visual interpretation. More quantitative efforts were directed at utilizing the reflected bands to define land cover classes and then modifying the thermal displays using long wave optical properties associated with cover type.

Source record↗
NASA NTRS1984

Analysis of carbon dioxide bands near 2.2 micrometers

Carbon dioxide is one of the more important atmospheric infrared-absorbing gases due to its relatively high, and increasing, concentration. The spectral parameters of its bands are required for understanding radiative heat transfer in the atmosphere. The line intensities, positions, line half-widths, rotational constants, and band centers of three overlapping bands of CO2 near 2.2 microns are presented. Non-linear least squares (NLLS) regression procedures were employed to determine these parameters.

Abubaker, M. S.↗
NASA NTRS1984

X-band Uplink Technology Demonstration at DSS-13

The status of the X-band uplink development program is examined from a systems' viewpoint. The hardware, designed and built under the program, is now in place at DSS-13. System stability testing is underway. An X-band receive capability is being implemented on both the Galileo and the Venus Radar Mapper spacecraft. Experiments are planned to demonstrate the capabilities of the X-band uplink system and to permit performance of the gravitational wave experiment on the Galileo orbiter and obtain a more detailed gravity map of Venus.

Meeker, J. G.↗
NASA NTRS1984

Evaluation of the Radiometric Integrity of LANDSAT-4 Thematic Mapper Band 6 Data

An approach for experimentally evaluating the radiometric calibration of the LANDSAT-4 band 6 data is described which draws on a method used to radiometrically calibrate the HCMR data which involved underflying the satellite with an infrared line scanner. By extending this technology to higher altitudes experimental radiance data suitable for radiometric calibration of the TM band 6 sensor can be generated. Repetition of this experiment can permit evaluation of long term drift in the sensor and provide a data base for evaluating atmospheric propagation models for radiation transfer. To date, efforts were concentrated on modifying the infrared line scanner to match the spectral response of the TM band 6 sensor. In addition, the LOWTRAN code corresponding to a satellite overpass of September 1982 was run to yield a plot of transmission and path radiance as a function of altitude.

Schott, J. R.↗
NASA NTRS1983

Monodeuterated methane in the outer solar system. I Spectroscopic analysis of the bands at 1.55 and 1.95 microns

The analysis of the near-infrared spectrum of monodeuterated methane (CH3D) near 6400/cm and 5100/cm is presented. Three new parallel bands which have locally perturbed upper states connecting with the ground state are identified, and approximate rotational constants are derived. The band centered near 6425/cm and the 9613 A band previously analyzed by Lutz, Danehy, and Ramsay (1978) are found to form an apparent vibrational progression with the nu2 fundamental at 2200/cm, and vibrational assignments of 3nu2 and 5nu2, respectively, are proposed. Detailed comparison of the rotational constants of the states involved is shown to support these assignments.

Lutz, B. L.↗
NASA NTRS1983

Absolute intensity measurements of the (11/1/0)II-00/0/0 band of (C-12)(O-16)2 at 5.2 microns

A nonlinear least-squares fitting procedure has been used to derive absolute intensities for lines in the P, R, and Q branches of the (11/1/0)II-00/0/0 band of (C-12)(O-16)2 (band center = 1932/cm) from long-path 0.01/cm resolution laboratory spectra. The spectral data were recorded at room temperature and low pressure (less than 10 torr) with the Fourier transform spectrometer in the McMath solar telescope complex at Kitt Peak National Observatory. The observed line intensities were analyzed to derive the vibrational band intensity and F-factor coefficients. To obtain a good fit to the data, it was necessary to include terms in the expression for the F factor, which account for Coriolis-type and Fermi-type interactions and centrifugal distortion effects.

Rinsland, C. P.↗
NASA NTRS1983

A Ka-band GaAs monolithic phase shifter

The design and performance of a GaAs monolithic 180-degree one-bit switched line phase shifter test circuit for Ka-band operation is presented. A self-aligned gate (SAG) fabrication technique is also described that reduces resistive parasitics in the switching FET's. Over the 27.5-30 GHz band, typical measured differential insertion phase is within 10-20 deg of the ideal time delay characteristic. Over the same band, the insertion loss for the SAG phase shifter is about 2.5-3 dB per bit. The SAG fabrication technique holds promise in reducing phase shifter insertion loss to about 1.5 dB/bit for 30-GHz operation.

Sokolov, V.↗
NASA NTRS1984

IUE observations of weak G-band stars

High- and low-resolution ultraviolet spectra of several weak G-band giants have been obtained with the IUE satellite, to derive Be abundances and to search for degenerate companions. The abundances of Be in these stars are about log epsilon (Be) approximately -0.5. These values are in good agreement with the Be abundances of Hyades giants, and are consistent with standard theories of post-main-sequence Be depletion in stars. However, the Be abundances do not fit with the large Li abundances in weak G-band stars. Post-main-sequence production of Li or element segregation in main-sequence stars may explain the high Li abundance in weak G-band stars. No direct evidence is seen for the presence of hot subluminous companions. The peculiar abundances in these stars probably are not due to binary mass transfer.

Parthasarathy, M.↗
NASA NTRS1984

The 12 micron band of ethane - High-resolution laboratory analysis with candidate lines for infrared heterodyne searches

Attention is given to the results of a laboratory study of the v9 band of ethane at 12 microns, using both high resolution Fourier transform and diode laser absorption spectroscopy. The analysis to which about 2000 transitions in this band have been subjected includes the normal rotational terms as well as the higher order effects of l-doubling, l-resonance, internal rotation, and a Coriolis resonance with the 3v4 state. A model is presented for the v9 band which is able to reproduce the observed features to an accuracy of better than 0.001/cm, and a list has been compiled for v9 transitions, occurring near C-14O2 laser lines, that are good candidates for laser heterodyne searches.

Atakan, A. K.↗
NASA NTRS1985

Measurement of the nighttime infrared luminosity of Spacelab 1 in the H- and K-bands

Infrared measurements of the Spacelab 1, Space Transportation System 9, were made from the Maui Optical Station tracking facility using a sensitive photometer n two infrared bands, the H-band centered at a wavelength of 1.6 microns and the K-band centered at 2.3 micrometers. The objective was to measure radiation from the vicinity of the Shuttle arising from interaction of Shuttle surfaces with atmospheric particles. It was necessary to include the Shuttle itself in the field of view of the photometer. The integrated brightness of the entire Shuttle at a distance of 400 km was found to be equivalent to that of a star of magnitude +6.6 or 1.6 microns; it was much fainter in the visible. Most of the emission at 1.6 microns appears to be attributable to the Shuttle glow phenomenon. It is hundreds of times brighter than the zodiacal background. The radiation at 2.3 microns can be accounted for primarily by diffusely scattered thermal radiation from Earth's surface.

Witteborn, F. C.↗