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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 613 records · Page 34
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NASA NTRS1977

The deep seismic structure of the moon

Data from 24 deep moonquakes are used to investigate the seismic structure of the lunar interior below the 300-500 km level. The deep moonquakes provide an uninterrupted ray-path coverage of the lunar mantle. Lower mantle seismic velocities are determined; the data suggest that moonquakes are confined to the near-side lower mantle. A compositional change rather than temperature effects is assumed to explain the upper mantle-lower mantle transition.

Goins, N. R.↗
NASA NTRS1977

Depositional history of the Apollo 16 deep drill core

Ferromagnetic resonance and magnetic hysteresis loop measurements were performed on 212 samples from the Apollo 16 deep drill core. The total iron content is generally uniform with a mean value of 5.7 plus or minus 0.9 wt%. The soils range in maturity from immature to mature. Two major contacts were observed. The contact at 13 cm depth represents a fossil surface whereas the contact at 190 cm depth has no time-stratigraphic significance. The data suggest that the core section below 13 cm depth was deposited in a single impact event and subjected to meteoritic gardening for about 450 m.y. However, our data do not preclude deposition by a series of closely spaced events. About 50 m.y. ago, the top 13 cm were added. Comparison with the Apollo 16 double drive tube 60009/60010 does not yield any evidence for a stratigraphic correlation with the deep drill core.

Gose, W. A.↗
NASA NTRS1978

The orbiting deep space relay station - A study report

This paper is an interim report on a study being carried out to assess the requirements for tracking and communications with deep-space probes in the post-1985 time frame and to evaluate approaches to meeting those requirements. The orbiting deep-space relay station (ODSRS) is one approach to meeting those requirements that appears to have some significant advantages over ground-based stations. A detailed conceptual design of an ODSRS is compared with other tracking and communications system configuration options. The comparison includes a life-cycle cost analysis as well as operations and performance capabilities. Reported results of the study to date include a preliminary assessment of post-1985 requirements, a discussion of planned ODSRS system capabilities as well as of tracking and communications system advantages and problems that are peculiar to an OSDRS, a look at the current status of the conceptual design of the ODSRS, and a summary of the plan for the remainder of the study.

Hunter, J. A.↗
NASA NTRS1979

The Deep Space Network

Deep Space Network progress in flight project support, tracking and data acquisition, research and technology, network engineering, hardware and software implementation, and operations is cited. Topics covered include: tracking and ground based navigation; spacecraft/ground communication; station control and operations technology; ground communications; and deep space stations.

Source record↗
NASA NTRS1979

Orbiting Deep Space Relay Station (ODSRS). Volume 1: Requirement determination

The deep space communications requirements of the post-1985 time frame are described and the orbiting deep space relay station (ODSRS) is presented as an option for meeting these requirements. Under current conditions, the ODSRS is not yet cost competitive with Earth based stations to increase DSN telemetry performance, but has significant advantages over a ground station, and these are sufficient to maintain it as a future option. These advantages include: the ability to track a spacecraft 24 hours per day with ground stations located only in the USA; the ability to operate at higher frequencies that would be attenuated by Earth's atmosphere; and the potential for building very large structures without the constraints of Earth's gravity.

Hunter, J. A.↗
NASA NTRS1979

PTTI applications to deep space navigation

Radio metric deep space navigation relies nearly exclusively upon coherent, two way, Doppler and ranging for all precise applications. These data types and the navigational accuracies they can produce are reviewed. The deployment of hydrogen maser frequency standards and the development of Very Long Baseline Interferometry (VLBI) systems within the Deep Space Network are used in the development of non-coherent, one way data forms that promise much greater inherent navigational accuracy. The underlying structure between each data class and clock performance is charted. VLBI observations of the natural radio sources are the planned instrument for the synchronization task. This method and a navigational scheme using differential measurements between the spacecraft and nearby quasars are described.

Curkendall, D. W.↗
NASA NTRS1979

Deep radio occultations and 'evolute flashes' - Their characteristics and utility for planetary studies

Deep radio occultation signals from spacecraft passing behind planets may provide data on atmospheric absorption, turbulence, and structure, as well as information on the effects of planetary gravitational moments, rotation and zonal winds on the atmospheric shape. The strength of radio signals from a spacecraft passing behind a planet will at first decrease because of defocusing in the atmosphere, but then increase as the evolute of the planetary limb is neared, due to focusing caused by limb curvature within the evolute. Within the evolute, the availability of four simultaneous signal paths over four limb positions may render focused signals instantaneously great. The passage of Voyager 1 behind Jupiter and Voyager 2 behind Saturn will provide a test of deep radio occultation studies.

Eshleman, V. R.↗
NASA NTRS1979

Space-based radio telescopes and an orbiting deep-space relay station

Foremost among the candidates for early utilization of the Shuttle-launched self-deployable structures are the space-based radio telescopes. Several space-based telescopes are examined including an orbiting VLBI terminal, an orbiting submillimeter telescope, and a large ambient deployable IR telescope. Particular consideration is given to the high-gain Orbiting Deep-Space Relay Station for communication with deep-space probes. Details of deployable antenna technology are discussed.

Powell, R. V.↗
NASA NTRS1980

Deep Space Station (DSS-13) automation demonstration

The data base collected during a six month demonstration of an automated Deep Space Station (DSS 13) run unattended and remotely controlled is summarized. During this period, DSS 13 received spacecraft telemetry data from Voyager, Pioneers 10 and 11, and Helios projects. Corrective and preventive maintenance are reported by subsystem including the traditional subsystems and those subsystems added for the automation demonstration. Operations and maintenance data for a comparable manned Deep Space Station (DSS 11) are also presented for comparison. The data suggests that unattended operations may reduce maintenance manhours in addition to reducing operator manhours. Corrective maintenance for the unmanned station was about one third of the manned station, and preventive maintenance was about one half.

Remer, D. S.↗
NASA NTRS1980

Deep space network energy program

If the Deep Space Network is to exist in a cost effective and reliable manner in the next decade, the problems presented by international energy cost increases and energy availability must be addressed. The Deep Space Network Energy Program was established to implement solutions compatible with the ongoing development of the total network.

Friesema, S. E.↗
NASA NTRS1979

Deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase-epitaxy n-GaAs

The paper presents deep-level transient spectroscopy studies of Ni- and Zn-diffused vapor-phase epitaxy n-GaAs. Nickel diffused into VPE n-GaAs reduces the hole diffusion length L sub p from 4.3 to 1.1 microns. Deep-level transient spectroscopy was used to identify energy levels in Ni-diffused GaAs; the as-grown VPE GaAs contains traces of these levels and an electron trap. Ni diffusion reduces the concentration of this level by an amount that matches the increase in concentration of each of the two Ni-related levels. A technique for measuring minority-carrier capture cross sections was developed, which indicates that L sub p in Ni-diffused VPE n-GaAs is controlled by the E sub c - 0.39 eV defect level.

Partin, D. L.↗
NASA NTRS1979

Characterization and depositional and evolutionary history of the Apollo 17 deep drill core

With a depth resolution of about 0.5 cm, the stratigraphy of the approximately 3 m Apollo 17 deep drill core by measurement of the total FeO concentration is characterized along with the FMR surface exposure (maturity) index Is/FeO, the metallic iron concentration Fe-vsm, and the FMR linewidth delta-H. For stratigraphic characterization, the first two parameters are the most important. Most of the core is characterized by a FeO concentration of approximately 15.5 wt. %; there is a more mafic zone in the upper approximately 75 cm where the maximum FeO concentration is approximately 18.5 wt. %, and a more felsic zone between approximately 225 and 260 cm where the minimum FeO concentration is approximately 14.0%. As indicated by Is/FeO, most of the soil in the core is submature to mature; the only immature zone is located between approximately 20 and 60 cm and is one of the most distinctive features in the core. A two stage model for the depositional and evolutionary history of the Apollo 17 deep drill core is proposed: (1) deposition by one event approximately 110 m.y. ago or deposition by a sequence of closely spaced events initating a maximum of approximately 200 m.y. ago and terminating approximately 110 m.y. ago, (2) in situ reworking (gardening) to a depth of approximately 26 cm in the period between approximately 110 m.y. ago and the present day.

Morris, R. V.↗
NASA NTRS1979

History of the Apollo 17 deep drill string during the past few million years

Measurements of the cosmogenic radionuclides 22-Na, 26-Al and 53-Mn in the Apollo 17 deep drill string 70002-70009 have shown that this core sample was taken in an area of considerable recent surface activity. Measurements of 22-Na indicate that the core had not been significantly altered during its collection and subsequent handling, while measurements of the 26-Al and 53-Mn showed a very substantial excess in these isotopes in the top 25 cm and a depletion below about 50 cm. The analysis of the data indicates that a crater excavation occurred to a depth of 50 to 60 cm at the site of the deep drill string no longer that 0.5 m.y. ago, and probably 0.3 m.y. ago. Since that time, the crater has filled to a depth of about 25 cm with near-surface material which contains high concentrations of 26-Al and 53-Mn. This recent activity at the site of the Apollo 17 drill string places firm time constraints on the models developed by other investigators which describe the history of this site.

Fruchter, J. S.↗
NASA NTRS1980

The fate of the downgoing slab - A study of the moment tensors from body waves of complex deep-focus earthquakes

Two large, complex deep-focus earthquakes are analyzed, using body waves, to determine the relative locations and equivalent forces of the component events. Details of the source mechanism determination are given, with special emphasis on the means of comparing results for double-couple and more general models. The formalism includes a description of a method for calculating the confidence ellipses around the principal axes of the moment tensor. An interpretation of the results suggests that the mechanism of deep-focus earthquakes is controlled by the buoyancy of the slab and the change in viscosity at the 650 km discontinuity.

Strelitz, R. A.↗
NASA NTRS1980

Deep convection on day 261 of GATE

The structural features of the deep convection observed on September 18, 1974, day 261 of the GARP Atlantic Tropical Experiment (GATE), as the ridge axis of a 700 mb wave passed the center of the GATE B-scale network are reported. Satellite and aircraft maps indicate the presence of clouds penetrating above 2.5 km into the middle troposphere organized in bands about 9 km apart and aligned roughly along the direction of the wind shear in the cloud layer. Radar echoes corresponding to cumulus convection of lifetime, peak height and peak rainfall rates on the orders of 30 min, 6 km and 1.3 mm/h, respectively, were observed to triple in number density as convergence at 950 hPa increased from 1.5 to 3 x 10 to the -5th/sec. The structural features of the radar echoes indicate that the day was similar to a mesoscale precipitation feature of Leary and Houe (1979), with the cluster consisting of many echoes appearing in succession. Data from aircraft penetrations of the deep convection reveal downdrafts accompanying the precipitation and updrafts immediately to their south. Shipboard and rawinsonde observations show that the convective downdrafts brought down air of low pseudo-equivalent potential temperature, with local surface convergence of up to 0.001/sec. Mean wind shears through the cloud layer to the top of a main cloud layer are found to be only 75% greater than those of Malkus (1958) for the Caribbean, with shears just above the cloud base several factors larger.

Warner, C.↗
NASA NTRS1980

Effects of thermal annealing on the deep-level defects and I-V characteristics of 200 keV proton irradiated AlGaAs-GaAs solar cells

Detailed characterization of deep-level defects and analysis of dark I-V data in 200 keV proton irradiated AlGaAs-GaAs solar cells have been carried out for several proton fluences (5 x 10 to the 11th, 10 to the 12th, and 10 to the 13th P/sq cm), using DLTS, C-V, and I-V measurement techniques. To study the effect of low temperature thermal annealing on the deep-level defect properties, these irradiated samples were annealed in vacuum at 300 C for one hour. Comparison was then made on the measured defect parameters (i.e., defect energy levels and densities) and the dark I-V characteristics for both the annealed and unannealed samples.

Li, S. S.↗
NASA NTRS1980

Study of radiation induced deep-level defects in proton irradiated AlGaAs-GaAs solar cells

Radiation induced deep-level defects (both electron and hole traps) in proton irradiated AlGaAs-GaAs p-n junction solar cells are investigated along with the correlation between the measured defect parameters and the solar cell performance parameters. The range of proton energies studied was from 50 KeV to 10 MeV and the proton fluence was varied from 10 to the 10th power to 10 to the 13th power P/sq cm. Experimental tools employed include deep-level transient spectroscopy, capacitance-voltage, current voltage, and SEM-EBIC methods. Defect and recombination parameters such as defect density and energy level, capture cross section, carrier lifetimes and effective hole diffusion lengths in n-GaAs LPE layers were determined from these measurements.

Li, S. S.↗
NASA NTRS1981

Electronic properties of deep-level defects in proton irradiated AlGaAs-GaAs solar cells

Deep level transient spectroscopy and capacitance voltage techniques as well as analysis of the forward current voltage (I-V) characteristics and SEM-EIC data were carried out for proton irradiated GaAs solar cells over a wide range of proton energies and proton fluences. Defect and recombination parameters such as defect energy levels and density, carrier capture cross sections and lifetimes as well as diffusion lengths in the undoped n-GaAs LPE layers were determined. Good correlation between these defect parameters and solar cell performance parameters was obtained for GaAs solar cells irradiated by 200 and 290 KeV protons. It was found that 200 to 290 KeV protons will produce the most defects and damages to the GaAs solar cell structure used. The influence of the low temperature (200 to 400 C) periodic thermal annealing on the deep level defects and the performance of the 200 KeV proton irradiated cells is discussed.

Li, S. S.↗