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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 199 records · Page 11
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

The Viking Relativity Experiment

Measurements of the round-trip time of flight of radio signals transmitted from the earth to the Viking spacecraft are being analyzed to test the predictions of Einstein's theory of general relativity. According to this theory the signals will be delayed by up to approximately 250 microsec owing to the direct effect of solar gravity on the propagation. A very preliminary qualitative analysis of the Viking data obtained near the 1976 superior conjunction of Mars indicates agreement with the predictions to within the estimated uncertainty of 0.5%.

Shapiro, I. I.↗
NASA NTRS1980

Propagation directions of hydromagnetic waves in interplanetary space - Pioneer 10 and 11

The real and imaginary parts of spectral matrices of magnetic field fluctuations near 4 and 5 AU are used separately to generate estimates of hydromagnetic wave normal directions over the frequency range 0.00001 to 0.01 Hz in the spacecraft frame. Both procedures suggest the predominance of the Alfven mode over the fast and slow MHD modes among transverse magnetic field perturbations. Both procedures also show that the Alfven mode is more common among transverse perturbations at 4 AU than at 5 AU. Statistical techniques are for estimating uncertainties in computed wave normal directions and it is concluded that the real parts of the spectral matrices are more useful than the imaginary parts in specifying wave normals at times of magnetic quiet in the solar wind near 4 and 5 AU.

Parker, G. D.↗
NASA NTRS1981

Satellite and correlative measurements of the stratospheric aerosol. II Comparison of measurements made by SAM II, dustsondes and airborne lidar

Results are shown from the first set of measurements conducted to validate extinction data from the Stratospheric Aerosol Measurement II (SAM II). Dustsonde-measured number density profiles and lidar-measured backscattering profiles for two days are converted to extinction profiles, and are shown to agree within their respective uncertainties at all heights above the tropopause. Near the tropopause, agreement depends on use of model size distributions with larger particles, having radii greater than 0.6 microns. The presence of such large particles is supported by measurements made elsewhere, is suggested by the in situ size distribution measurements reported, and is likely to have an important bearing on the radiative impact of the total stratospheric aerosol. It is concluded that the SAM II extinction data and uncertainty estimates are supported.

Russell, P. B.↗
NASA NTRS1982

A calibration line list for 807-1167 cm -1 from high resolution Fourier spectroscopy of the 14NH3 nu sub 2 band

A calibration list of 295 lines observed over the 800 to 1170 cm to the -1 power region is presented. This list is intended for use as a calibration reference for calibrating diode laser spectra. The transition frequencies were calibrated against the well established laser frequencies of CO2. The estimated uncertainty in the corrected frequencies is + or - 1x.0001 cm to the -1 power.

Hillman, J. J.↗
NASA NTRS1981

The current status of REH theory

A response is made to the evaluation of Fitch (1980) of REH (random evolutionary hits) theory for the evolutionary divergence of proteins and nucleic acids. Correct calculations for the beta hemoglobin mRNAs of the human, mouse and rabbit in the absence and presence of selective constraints are summarized, and it is shown that the alternative evolutionary analysis of Fitch underestimates the total fixed mutations. It is further shown that the model used by Fitch to test for the completeness of the count of total base substitutions is in fact a variant of REH theory. Considerations of the variance inherent in evolutionary estimations are also presented which show the REH model to produce no more variance than other evolutionary models. In the reply, it is argued that, despite the objections raised, REH theory applied to proteins gives inaccurate estimates of total gene substitutions. It is further contended that REH theory developed for nucleic sequences suffers from problems relating to the frequency of nucleotide substitutions, the identity of the codons accepting silent and amino acid-changing substitutions, and estimate uncertainties.

Holmquist, R.↗
NASA NTRS1982

New results from the Viking relativity experiment

The predicted general relativistic effect of solar gravity on the round-trip times of electromagnetic signals traveling between earth and Mars has been verified by means of radio ranging to the Viking spacecraft. The ranging measurements were found to be consistent with the predicted increases of up to 200 microsec in the travel times of the signals to within the estimated uncertainty of 0.2%.

Reasenberg, R. D.↗
NASA NTRS1982

Preliminary risk benefit assessment for nuclear waste disposal in space

This paper describes the recent work of the authors on the evaluation of health risk benefits of space disposal of nuclear waste. The paper describes a risk model approach that has been developed to estimate the non-recoverable, cumulative, expected radionuclide release to the earth's biosphere for different options of nuclear waste disposal in space. Risk estimates for the disposal of nuclear waste in a mined geologic repository and the short- and long-term risk estimates for space disposal were developed. The results showed that the preliminary estimates of space disposal risks are low, even with the estimated uncertainty bounds. If calculated release risks for mined geologic repositories remain as low as given by the U.S. DOE, and U.S. EPA requirements continue to be met, then no additional space disposal study effort in the U.S. is warranted at this time. If risks perceived by the public are significant in the acceptance of mined geologic repositories, then consideration of space disposal as a complement to the mined geologic repository is warranted.

Rice, E. E.↗
NASA NTRS1982

Water vapor measurement system in global atmospheric sampling program, appendix

The water vapor measurement system used in the NASA Global Atmospheric Sampling Program (GASP) is described. The system used a modified version of a commercially available dew/frostpoint hygrometer with a thermoelectrically cooled mirror sensor. The modifications extended the range of the hygrometer to enable air sample measurements with frostpoint temperatures down to -80 C at altitudes of 6 to 13 km. Other modifications were made to permit automatic, unattended operation in an aircraft environment. This report described the hygrometer, its integration with the GASP system, its calibration, and operational aspects including measurement errors. The estimated uncertainty of the dew/frostpoint measurements was + or - 1.7 Celsius.

Englund, D. R.↗
NASA NTRS1984

Photometric standard stars for L' and M filter bands

L' (3.8 microns) and M (4.9 microns) photometry of 20 primary and 21 secondary standard stars that are sufficiently faint for large telescope observation is presented. The estimated uncertainties in the magnitudes of the primary standards are 0.01 at L', 0.02 at M, and 0.015 for the L'-M color. A color transformation between the present L' magnitudes and the L magnitudes of Elias et al. (1982) is obtained and found to be near agreement with that predicted for black-bodies.

Sinton, W. M.↗
NASA NTRS1985

Ab initio study of BeCN, MgCN, CaCN and BaCN

The structure and energetics of the BeCN, MgCN, CaCN and BaCN molecules are studied at both the Hartree-Fock and singles plus doubles configuration-interaction level using Gaussian basis sets of at least triple-zeta plus double polarization quality. All molecules are predicted to be linear, with the isocyanide structures more stable by 0.3 to 0.5 eV than the corresponding cyanides. The theoretical dissociation energies (De) in eV with an estimated uncertainty are (with the experimental values in parentheses): Be-NC 4.2 + or - 0.1 (4.46 + or - 0.29), Mg-NC 3.45 + or - 0.1 (4.21 + or - 0.22), Ca-NC 4.2 + or - 0.1 (4.46 + or - 0.22) and Ba-NC 4.5 + or 0.2 (4.87 + or - 0.26).

Bauschlicher, C. W., Jr.↗
NASA NTRS1986

The luminosities of the binary cepheids SU Cyg, SU Cas and W Sgr

Absolute magnitudes for binary classical Cepheids were derived by ratioing IUE low dispersion spectra in regions where the blue companion dominates with spectra of main sequence spectral type standards. The IUE spectra are also used to determine the magnitude difference between the Cepheid and the blue companion. Absolute magnitudes determined for SU Cyg and W Sgr agree with the absolute magnitudes of Sandage and Tammann and Caldwell within the + or - 0m2 estimated uncertainty, but not with the fainter absolute magnitudes of Schmidt. The absolute magnitude of SU Cas is in better agreement with the PLC relations if it is pulsating in the first overtone mode.

Evans, Nancy Remage↗
NASA NTRS1986

Doppler lidar atmospheric wind sensors - A comparative performance evaluation for global measurement applications from earth orbit

A comparison is made of four prominent Doppler lidar systems, ranging in wavelength from the near UV to the middle IR, which are presently being studied for their potential in an earth-orbiting global tropospheric wind field measurement application. The comparison is restricted to relative photon efficiencies, i.e., the required number of transmitted photons per pulse is calculated for each system for midtropospheric velocity estimate uncertainties ranging from + or - 1 to + or - 4 m/s. The results are converted to laser transmitter pulse energy and power requirements. The analysis indicates that a coherent CO2 Doppler lidar operating at 9.11-micron wavelength is the most efficient.

Menzies, R. T.↗
NASA NTRS1986

The mass of the Coma cluster

Mass estimate uncertainties for the Coma cluster in position and velocity data for the galaxies are examined under the assumption that mass and galaxy distribution are parallel, on the one hand, and on the other, that the form of the mass distribution is not constrained. While low mass models have all the mass in the cluster core, and require the galaxies to be on or near circular orbits, high mass models are noted to have weakly concentrated mass distributions and primarily radial orbits. It is concluded that galaxy data alone are unlikely to clearly distinguish between these possibilities.

The, Lih Sin↗
NASA NTRS1986

The vapor pressures of solid and liquid ozone

Vapor pressures of solid and liquid ozone have been measured over a temperature range 87 to below 66 K. The experiment was performed under flow conditions, and the gas was analyzed by a precision mass spectrometer system. In the range of solid ozone two forms, supercooled and crystalline ozone, were found. A least-square fit of the data for crystalline ozone resulted in the equation log P(torr) = A + B/T, where A = 10.460 and B = -1021.6. The estimated uncertainty of the data is + or - 1.0 percent. A triple-point temperature of 79.6 + or - 0.3 K was found where supercooled and crystalline ozone data intersect.

Hanson, David↗
NASA NTRS1988

A Design Study of Onboard Navigation and Guidance During Aerocapture at Mars

The navigation and guidance of a high lift-to-drag ratio sample return vehicle during aerocapture at Mars are investigated. Emphasis is placed on integrated systems design, with guidance algorithm synthesis and analysis based on vehicle state and atmospheric density uncertainty estimates provided by the navigation system. The latter utilizes a Kalman filter for state vector estimation, with useful update information obtained through radar altimeter measurements and density altitude measurements based on IMU-measured drag acceleration. A three-phase guidance algorithm, featuring constant bank numeric predictor/corrector atmospheric capture and exit phases and an extended constant altitude cruise phase, is developed to provide controlled capture and depletion of orbital energy, orbital plane control, and exit apoapsis control. Integrated navigation and guidance systems performance are analyzed using a four degree-of-freedom computer simulation. The simulation environment includes an atmospheric density model with spatially correlated perturbations to provide realistic variations over the vehicle trajectory. Navigation filter initial conditions for the analysis are based on planetary approach optical navigation results. Results from a selection of test cases are presented to give insight into systems performance.

Fuhry, Douglas Paul↗
NASA NTRS1987

Tunable diode laser measurements of absolute linestrengths in the HNO3 band near 5.8 microns

Absolute line strengths of selected lines in the nu 2 band of HNO3 have been measured using a tunable diode laser spectrometer operating in a sweep integration mode. The direct measurement technique has been employed to obtain line intensities at 296 K for 22 isolated lines in the 1720-1725/cm region. The reported line strengths have estimated uncertainties of 4 percent, a significant portion of this uncertainty arising from spectral interference from hot band transitions. From these line-strength measurements, an integrated band intensity of 1375/sq cm per atm at 296 K is inferred.

May, Randy D.↗
NASA NTRS1988

Global trends in total ozone

Satellite ozone data from the Total Ozone Mapping Spectrometer from 1979 through 1986 show that recent decreases of total ozone have not been confined to the Antarctic spring season (the Antarctic ozone hole), but are global in extent. The losses are about twice the estimated uncertainty in the satellite data. The decreases are largest in middle and high latitudes and occur in all seasons of the year. The decreases for this 8-year period are comparable in magnitude to the increases observed during the 1960s. Southern Hemisphere values from 1986 are generally greater than those from 1985.

Bowman, Kenneth P.↗
NASA NTRS1987

The luminosities of the binary Cepheids SU Cyg, SU Cas, and W Sgr

Absolute magnitudes for binary classical Cepheids were derived by ratioing IUE low dispersion spectra in regions where the blue companion dominates with spectra of main sequence spectral type standards. The IUE spectra are also used to determine the magnitude difference between the Cepheid and the blue companion. Absolute magnitudes determined for SU Cyg and W Sgr agree with the absolute magnitudes of Sandage and Tammann and Caldwell within the + or - Om2 estimated uncertainty, but not with the fainter absolute magnitudes of Schmidt. The absolute magnitude of SU Cas is in better agreement with the PLC relations if it is pulsating in the first overtone mode.

Evans, Nancy Remage↗