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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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NASA NTRS1981

HEAO A-2 observations of non-Abell Zwicky clusters containing extended radio sources

Burns and Owen's sample of 25 4C radio sources which coincide with Zwicky clusters of galaxies has been searched for X-ray emission using the HEAO 1 A-2 experiment. X-ray emission was detected from five sources at the 3sigma level, two of which exceeded 5sigma. Positions and 90% X-ray error boxes are given for each of the five sources detected. The clusters surveyed are non-Abell clusters which would generally not be expected to be detectable with the A-2 experiment. The search for X-ray emission was prompted by the knowledge of the existence of extended radio sources in the clusters. The relaxed structure of these sources implies the presence of a relatively dense intracluster medium which is expected to produce thermal bremsstrahlung X-ray emission.

Holman, G. D.↗
NASA NTRS1982

Microwave spectra of terrestrial mesospheric CO

Mesospheric CO was observed in absorption against the moon in early December 1979 at a wavelength of 1.3 mm and in early December 1980 at 2.6 mm with the 10.4-m millimeter wavelength telescope at the Owens Valley Radio Observatory. No significant change in the column density of CO above about 65 km is found between the 1979 and 1980 observations. Comparison with other published spectra of mesospheric CO suggests a large seasonal variation (about a factor of 2-3) in the column density of CO above 65 km, with a maximum in winter and a minimum in summer. It is concluded that the understanding of CO in the mesosphere can be improved with earth-based microwave measurements, but data with high signal-to-noise ratios must be obtained.

Clancy, R. T.↗
NASA NTRS1982

Statistical tests of ARIES data

Statistical tests are performed on Project ARIES preliminary baseline measurements in the Southern California triangle formed by the Jet Propulsion Laboratory, the Owens Valley Radio Observatory, and the Goldstone tracking complex during 1976-1980. In addition to conventional one-dimensional tests a two-dimensional test which allows for an arbitrary correlation between errors in individual components is formulated using the Hotelling statistic. On two out of three baselines the mean rate of change in baseline vector is statistically significant. Apparent motions on all three baselines are consistent with a pure shear with north-south compression and east-west expansion of 1 x 10 to the -7th/year. The ARIES measurements are consistent with the USGS geodolite networks in Southern California and the SAFE laser satellite ranging experiment. All three experiments are consistent with a 6 cm/year motion between the Pacific and North American Plates and a band of diffuse shear 300 km wide, except that corresponding rotation of the entire triangle is not found.

Musman, S.↗
NASA NTRS1982

Radio interferometric detection of a traveling ionospheric disturbance excited by the explosion of Mount St. Helens

A large-amplitude traveling ionospheric disturbance (TID) was detected over Owens Valley, California, on May 18, 1980, by a highly sensitive very long baseline interferometry (VLBI) radio astronomy experiment. This TID is interpreted as the response of the ionosphere to a gravity wave excited in the neutral atmosphere by the explosion of Mount St. Helens that took place at 1532 UT on that day. A model, invoking the point-excitation of internal gravity waves in an isothermal atmosphere, which fits observations of the TID at several other stations, leads to identification of the features observed in the VLBI data. Small-amplitude higher-frequency changes in the ionosphere were detected for several hours after the passage of the large-amplitude Mount St. Helens TID, but it is not clear whether these were excited by the passage of the gravity wave or were background fluctuations.

Roberts, D. H.↗
NASA NTRS1983

Interagency Array Study Report

The interagency array study that was convened in early 1982 to determine which of the world's large radio reception facilities might be feasibly and beneficially enlisted to help support the Voyager encounters at Uranus (1986) and Neptune (1989), and also to examine the future for such similar events and options as might appear is discussed. A similar but more specific study of the Parkes Radio Telescope at Uranus Encounter was just then being completed with a strong positive recommendation, and formed the foundation of the broader study. The approach, driving considerations, and outcome of the interagency array study are discussed. The recommendations of the study team concentrated upon the Voyager Encounters are: specifically to develop Parkes for the Uranus Encounter, while pursuing related Advanced Systems development work with the Owens Valley Radio Observatory, and to seek support for the Neptune Encounter from Parkes, the Very Large Array near Socorro, Mexico, and the Japanese institute of Space and Astronautical Sciences 64 meter station.

Wayland, J. W.↗
NASA NTRS1983

The NASA/GSFC hydrogen maser program: A review of recent data

Data is presented on the phase and frequency stability, over time periods extending to one week, of the new NR field operable hydrogen masers developed by the Applied Physics Laboratory (APL) and the older NX and NP field operable hydrogen masers developed by Goddard Space Flight Center and maintained and upgraded by Bendix Field Engineering Corporation (BFEC). Data is presented on the NR masers in the laboratory showing frequency stabilities well into the 10 to the -15th power range and phase stabilities well into the 100 ps range for periods of up to one day. Data is presented on upgraded NP masers in the laboratory showing that the frequency stability has been improved substantially to virtually the NR level. VLBI data is presented on the phase difference between NX-2 at Owens Valley, California and NR-2 at Fort Davis, Texas for a one week period showing, after removal of a constant frequency drift, a 350 ps RMS phase stability.

Chiu, M.↗
NASA NTRS1983

Very long baseline interferometry at a wavelength of 3.4 mm

The first detection of interference fringes by VLBI at a wavelength of 3.4 mm during observations of 3C84 are reported. The compact source in the nucleus of 3C84 was observed for a 9-hr period on the 485 km baseline between the Owens Valley Radio Observatory and the Hat Creek Observatory. The fringe data are given and the derivation of the correlated flux densities is described. The findings are discused in the context of previous obervations. The results demonstrate that there are no unforeseen technical difficulties associated with millimeter VLBI, and that the sensitivity of existing systems is sufficient to observe objects brighter than a few Jy. The observations are consistent with the millimeter wavelength radio structure of 3C84 being more compact than its centimeter wavelength structure.

Readhead, A. C. S.↗
NASA NTRS1983

A helium-3 cooled bolometer system for one millimeter continuum observations

A new, 1-mm-continuum, bolometer detector system has been constructed employing internal adsorption pumping of He-3 to reach an operating temperature close to 0.4 K. The system spectral bandwidth is 800 to 1200 microns. Although the system was originally designed to be used on the 5-m Hale telescope, it has also been successfully used on the 4-m Anglo-Australian telescope and on the 10-m dish at Owens Valley, California. At the 5-m Hale telescope, the system has a full width-half maximum (FWHM) beam size of 55 sec and an instantaneous noise-equivalent flux density of 6 Jy/square root of (Hz)/ in good weather.

Roellig, T. P. L.↗
NASA NTRS1983

Precise spacecraft tracking using VLBI digital tone extraction for the purpose of gravitational wave detection

The prospect for the detection of a cosmic background of gravitational wave radiation is discussed. Experiments utilizing precise Doppler tracking of interplanetary spacecraft for the purpose of detecting this background are reviewed. Results of a recent experiment are presented which used facilities of NASA's Deep Space Tracking Network and Owens Valley Radio Observatory to track the Voyager spacecraft in an ultra precise manner using two independent hydrogen masers as frequency standards. The present limiting sensitivity of these experiments are believed to be tropospheric and plasma variations affecting the X band microwave signals at periods of between 1,000 - 10,000 seconds duration.

Anderson, A. J.↗
NASA NTRS1985

Vegetation analysis for arid lands geobotany

Three primary study sites were selected for measurement of plant phenological properties and spectral analysis. The sites selected represented typical sagebrush, creosote bush, and saltbush communities in Owens Valley, CA. Community composition was studied at these three sites plus five burned sites. Ten 50 m transects at each locality were measured for percent cover (over 10 cm) by a given species. On each transect two point quarter and five nearest neighbor analyses were conducted. These data provided percent cover, cover by area, plant size, tendency for association, and recolonization patterns after a disturbance. Plots representing percentage plant cover for six sites are included.

Barbour, M. G.↗
NASA NTRS1984

Experimental studies of glass refining

The basic components of the experimental apparatus were selected and acquired. Techniques were developed for the fabrication of the special crucibles necessary for the experiments. Arrangements were made for the analysis of glass and gas bubble samples for composition information. Donations of major equipment were received for this project from Owens, Illinois where a similar study had been conducted a few year ago. Decisions were made regarding the actual glass composition to be used, the gas to be used in the first experiments, and the temperatures at which the experiments should be conducted. A microcomputer was acquired, and work was begun on interfacing the video analyzer to it.

Subramanian, R. S.↗
NASA NTRS1984

C-13H3OH in OMC-1

Transition line data for C-13H3OH in OMC-1 were gathered with a superconducting tunnel junction receiver and a 512 channel spectrometer on a 10.4 m telescope at the Owens Valley Radio Observatory. The methanol was scanned at 236 GHz and an observational efficiency of 85 percent. The survey was carried out to complement the data base on the line frequencies of internal rotors such as methanol and thereby the resolution of the C-12/C-13 ratio toward the galactic center. The data indicated that previous emission lines attributed to CO(+) and CH3CHO are actually methanol emissions, and the associated C-12/C-13 ratio is about 30.

Blake, G. A.↗
NASA NTRS1985

Dual polarization VLBI observations of stellar binary systems at 5 GHz

The binary systems Sigma CrB, SZ Psc, HR 1099, UX Ari, HR 5110, Algol, and Cyg X-1 are characterized in terms of marcsec-scale radio structure on the basis of dual-polarization observations at 4.969-4.997 GHz, obtained with an international VLBI array comprising the 100-m Effelsberg, 36-m Haystack, 42-m Green Bank, 26-m Fort Davis, 130-m-equivalent VLA, and 40-m Owens Valley telescopes (system temperatures 40-70 K) at 22-14 h UT on July 26-27, 1983. The data are presented in graphs and tables and discussed in detail. Single Gaussian brightness distributions with theta(FWHM) = 0.5-2.0 marcsec and brightness temperatures (2-200) x 10 to the 8th K are determined for four sources; core-halo structures are found for UX Ari and Algol; and an upper limit of 50 microarcsec is established for the angular separation of the regions of left and right circular polarization. The gross features seen in RS CVn systems are explained in terms of a simple expanding-coronal-loop model of flare events.

Mutel, R. L.↗
NASA NTRS1985

A diffuse plate boundary model for Indian Ocean tectonics

It is suggested that motion along the virtually aseismic Owen fracture zone is negligible, so that Arabia and India are contained within a single Indo-Arabian plate divided from the Australian plate by a diffuse boundary. The boundary is a zone of concentrated seismicity and deformation commonly characterized as 'intraplate'. The rotation vector of Australia relative to Indo-Arabia is consistent with the seismologically observed 2 cm/yr of left-lateral strike-slip along the Ninetyeast Ridge, north-south compression in the Central Indian Ocean, and the north-south extension near Chagos.

Wiens, D. A.↗
NASA NTRS1985

Age-dating volcanic and alluvial surfaces with multipolarization data

A false-color multipolarization version of one of the images of Owens Valley area acquired by the JPL Synthetic Aperture Radar (SAR) is given. A geologic map of the alluvial fans there (Gillespie, 1982) is also given for comparison. In general, brightness in the multipolarization images can be seen to be inversely proportional to the age of the surfaces. A more detailed investigation of the relationship between backscatter and age of the surfaces was undertaken with calibrated aircraft SAR data. The quantitative relationship between backscatter coefficient and age for the three polarizations is shown. The straight lines connecting the measured data points imply a steady-state process, although the process or processes leading to this relationship may have operated at rates that varied with climate fluctuations, such as the glacial ages. It is expected that the relationship between radar brightness and age is a consistent one, and that with the wider availability of calibrated radar backscatter data, these relationships can be less well-known areas. The effect of variable such as past climate fluctuations, tectonic disturbance, and rock type must be understood before extension beyond the Mojave Desert region can be attempted.

Farr, T. G.↗
NASA NTRS1985

Strategies for analyzing mixed pixels in remotely sensed imagery

Two uncalibrated synthetic aperture radar (SAR) scenes from Death Valley, California, and two uncalibrated scenes from Owens Valley, California, were used to test a technique to identify and separate the primary factors associated with multipolarized radar image sets. Unique to the technique is the concept that varied types of radar polarization signatures are a result of the interaction of a few physical factors (e.g., roughness, volume scattering, and dielectric constant). Thus, the varied signatures observed in an image reflect the interaction between these factors. The objectives are to first separate the interaction of factors directly influencing the measurement and to attempt to identify these factors. Interpretation of the SAR image sets proceeds by testing models that hypothesize the cause and effect relations between those factors directly affecting the radar measurement and those features of interest to the interpreter. The results of our analysis indicated two consistent endmember types over all four image scenes. These types are defined by a high flat polarized signature near a level of 255 DN and a low level flat signature near 0 DN for all polarizations. Four other endmember types were also isolated. The spatial distribution of these endmember types indicates possible correspondence to surface volume scattering and changes in surface dielectric. However, the shapes of these endmember types were different from scene to scene.

Smith, M.↗
NASA NTRS1986

High-spectral resolution solar microwave observations

The application of high-spectral resolution microwave observations to the study of solar activity is discussed with particular emphasis on the frequency dependence of microwave emission from solar active regions. A shell model of gyroresonance emission from active regions is described which suggest that high-spectral resolution, spatially-resolved observations can provide quantitative information about the magnetic field distribution at the base of the corona. Corresponding observations of a single sunspot with the Owens Valley frequency-agile interferometer at 56 frequencies between 1.2 and 14 Ghs are presented. The overall form of the observed size and brightness temperature spectra was consistent with expectations based on the shell model, although there were differences of potential physical significance. The merits and weaknesses of microwave spectroscopy as a technique for measuring magnetic fields in the solar corona are briefly discussed.

Hurford, G. J.↗
NASA NTRS1986

The March 1985 demonstration of the fiducial network concept for GPS geodesy: A preliminary report

The first field tests in preparation for the NASA Global Positioning System (GPS) Caribbean Initiative were conducted in late March and Early April of 1985. The GPS receivers were located at the POLARIS Very Long Base Interferometry (VLBI) stations at Westford, Massachusetts; Richmond, Florida; and Ft. Davis, Texas; and at the Mojave, Owens Valley, and Hat Creek VLBI stations in California. Other mobile receivers were placed near Mammoth Lakes, California; Pt. Mugu, California; Austin, Texas; and Dahlgren, Virginia. These sites were equipped with a combination of GPS receiver types, including SERIES-X, TI-4100 and AFGL dual frequency receivers. The principal objectives of these tests were the demonstration of the fiducial network concept for precise GPS geodesy, the performance assessment of the participating GPS receiver types, and to conduct the first in a series of experiments to monitor ground deformation in the Mammoth Lakes-Long Valley caldera region in California. Other objectives included the testing of the water vapor radiometers for the calibration of GPS data, the development of efficient procedures for planning and coordinating GPS field exercise, the establishment of institutional interfaces for future cooperating ventures, the testing of the GPS Data Analysis Software (GIPSY, for GPS Inferred Positioning SYstem), and the establishment of a set of calibration baselines in California. Preliminary reports of the success of the field tests, including receiver performance and data quality, and on the status of the data analysis software are given.

Davidson, J. M.↗