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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Moderately volatile elements

That the fractionation of moderately volatile and highly volatile elements was a major process in the early solar system is reflected in the variable concentrations of Rb and associated variations in initial Sr-isotopic ratios in chondritic meteorites. Greater knowledge of processes leading to volatile depletion would place stronger constraints on the formation conditions of solid material in the solar system. It will especially become possible to ascertain whether evaporation or incomplete condensation was the major process in establishing the elemental abundance patterns observed in primitive meteorites and planets.

Palme, H.↗
NASA NTRS1990

The Moderate Resolution Imaging Spectrometer (MODIS)

The Moderate Resolution Imaging Spectrometer (MODIS) observing facility on the Earth Observing System (EOS) is composed of two instruments, MODIS-Nadir (N) and MODIS-Tilt (T). MODIS-N has 36 spectral bands between 0.4 and 14.2 micrometers with spatial resolution between 214 and 856 meters. MODIS-T has 32 bands with 10-15 nanometer bandwidths between 0.4 and 0.9 micrometers. MODIS-T scans fore and aft + or - 50 degrees. Both instruments scan cross-track so as to provide daily (MODIS-N) or once every 2 days (MODIS-T) coverage at 705 kilometers altitude. Both instruments are entering into the execution phases of their development in 1990.

Salomonson, Vincent V.↗
NASA NTRS1990

Vibrations of rectangular plates with moderately large initial deflections at elevated temperatures using finite element method

A finite-element formulation is developed for the free vibration of rectangular plates which are under the influence of moderately large stress-free initial deflections and large thermal deflections. The von Karman nonlinear strain-displacement relations are used to account for the thermal deflections. The plates are thin, isotropic, and Hookean in nature. The temperature imposed on the plate is assumed to be constant through the thickness of the plate. Uniform and sinusoidal temperature distributions are studied. The material properties of the plates are temperature-dependent due to the relatively high temperatures imposed on the plates.

Gray, C. C.↗
NASA NTRS1990

Convective heat flow in space cryogenics plugs - Critical and moderate He II heat flux densities

Plug flow rates of entropy, heat and normal fluid in phase separators and in zero net mass flow systems are, to some extent, quite similar. A simplified analysis of critical conditions is presented in agreement with data trends. A critical temperature gradient arises on the basis of the He II two-fluid model at the stability limit constraining the thermohydrodynamics of the system. Thus, the question of critical thermodynamic fluctuations associated with nucleation versus the possibility of critical gradients in externally imposed parameters is answered in favor of the latter route toward turbulence. Furthermore, a similarity equation is presented which incorporates size dependent rates for moderate heat flow densities observed in experiments.

Yuan, S. W. K.↗
NASA NTRS1990

Measurements of sea spikes in microwave backscatter at moderate incidence

Quantitative measurements of the relationship between the friction velocity and sea spikes in the mean normalized radar cross section (MNRCS) are presented. The intensity threshold for the definition of sea spike contribution to the MNRCS is used to count large sea spikes associated with a positive mean Doppler frequency. The proposed method is applied to Ku-band measurements made with a dual-polarized Doppler scatterometer at a moderate incidence angle from a fixed platform in the North Sea. The variation of the sea spike contribution to the MNRCS with friction velocity was found to be consistent with Phillips' (1988) prediction of a cubic dependence.

Jessup, A. T.↗
NASA NTRS1990

Broadband shock-associated noise of moderately imperfectly expanded supersonic jets

Recently a stochastic model theory of broadband shock-associated noise from supersonic jets was developed. The theory is capable of predicting the near and far field noise spectra of slightly imperfectly expanded jets. In this paper, the noise prediction formulas are extended to the moderately imperfectly expanded Mach number range. It is found that the shock noise intensity depends only on the amplitude of the quasi-periodic shock cell structure and not on the strong first shock. This makes it possible to extend the noise prediction formulas by simply modifying the shock cell strength in the original formulas. Here this step is implemented semiempirically, and a set of shock noise prediction formulas are developed.

Tam, C. K. W.↗
NASA NTRS1989

The moderate resolution imaging spectrometer data system

Science requirements for a moderate resolution imaging spectrometer (MODIS) data system are outlined, as well as the operations concept and system specifications based on these requirements. Two systems are considered - MODIS-N for a 40-channel nadir-viewing scanner and MODIS-T for a 64-channel tiltable scanner. The first system collects data from 15 thermal-infrared channels at all times and from 25 reflected-energy channels during daytime, while MODIS-T will take data from 64 channels on a 100-percent duty cycle during daytime only. Standard data products, data acquisition and processing, and requirements on data are discussed. Emphasis is placed on the interfaces between the science data processing facilities and the scientific users.

Han, Daesoo↗
NASA NTRS1991

Static strain and vibration characteristics of a metal semimonocoque helicopter tail cone of moderate size

The results are presented of an analytic and experimental research program involving a Sikorsky S-55 helicopter tail cone directed ultimately to the improved structural analysis of airframe substructures typical of moderate sized helicopters of metal semimonocoque construction. Experimental static strain and dynamic shake-testing measurements are presented. Correlation studies of each of these tests with a PC-based finite element analysis (COSMOS/M) are described. The tests included static loadings at the end of the tail cone supported in the cantilever configuration as well as vibrational shake-testing in both the cantilever and free-free configurations.

Bielawa, Richard L.↗
NASA NTRS1989

Moderate Resolution Imaging Spectrometer - A progress report (April 1989)

The Moderate Resolution Imaging Spectrometer (MODIS) is a facility instrument to be flown on the first Earth Observing System (scheduled launch in the late 1990s). The MODIS has two components. One component is a 110-deg-scan-angle instrument called MODIS-N (nadir). This instrument has 40 selected bands supporting observations of the land surface, the oceans, and atmosphere in the visible, NIR, short-wave IR (1.0-3.0 microns), and thermal IR (3.0-15.0 microns). The other component is a 90-deg-scan-angle scanning instrument that can tilt fore and aft along the satellite track, called MODIS-T (tilt). Both MODIS-N and MODIS-T are nearing the end of detailed design studies. The driving scientific requirements include absolute calibration accuracy 2 percent, instrument-induced polarization less than 2 percent, SNR reaching 800:1 for observing ocean color at large solar zenith angles, and dynamic range allowing observations of cloud characteristics and snow-covered areas.

Salomonson, V. V.↗
NASA NTRS1989

Jet streak circulations associated with a moderate snowfall event as diagnosed from NGM model output

The existence, evolution, and interaction of vertical circulations associated with upper-level jet streaks during a moderate snowfall event are diagnosed using a nested grid model (NGM). The event itself is overviewed, and the diagnosis of transverse circulations utilizing NGM output is discussed. Focus is placed on the identification of the horizontal and vertical components of the circulation, the temporal evolution of the circulation, and the comparison of the circulation from successive model forecasts. A preliminary analysis of the model data indicates that the horizontal and vertical branches of the circulations can be diagnosed from the model output, and the horizontal and vertical components of the circulations may be identified and followed during an individual forecast cycle.

Kocin, Paul J.↗
NASA NTRS1991

The moderate resolution imaging spectrometer (MODIS) science and data system requirements

The Moderate Resolution Imaging Spectrometer (MODIS) has been designated as a facility instrument on the first NASA polar orbiting platform as part of the Earth Observing System (EOS) and is scheduled for launch in the late 1990s. The near-global daily coverage of MODIS, combined with its continuous operation, broad spectral coverage, and relatively high spatial resolution, makes it central to the objectives of EOS. The development, implementation, production, and validation of the core MODIS data products define a set of functional, performance, and operational requirements on the data system that operate between the sensor measurements and the data products supplied to the user community. The science requirements guiding the processing of MODIS data are reviewed, and the aspects of an operations concept for the production of data products from MODIS for use by the scientific community are discussed.

Ardanuy, Philip E.↗
NASA NTRS1991

Design considerations of PSR moderate focus-mission structure

A supporting space-frame has been designed for the segmented panels, secondary reflector, control system, and interface hardware of a near-term Precision Segmented Reflector (PSR) telescope. In addition to meeting areal mass density, vibration frequency, thermal expansion, positioning accuracy, and interface attachment design goals, the PSR structure must withstand Atlas launch loads. Analyses have been conducted of the optical pointing-related structural performance of the Moderate Focus Mission Structure (MFMS), with a view to both mechanical and thermal disturbance analyses; the results indicate that the dynamic responses of the MFMS optical mirrors, due to the chopping disturbance of the secondary reflector about its center-of-mass, are within maintenance sensor requirements.

Shih, Choon-Foo↗
NASA NTRS1991

Execution phase (C/D) spectral band characteristics of the EOS moderate resolution imaging spectrometer-Nadir (Modis-N) facility instrument

The Moderate Resolution Imaging Spectrometer (Modis) observing facility on the Earth Observing System (EOS) is composed of two instruments: Modis-Nadir (N) and Modis-Tilt (T). Modis-N has 36 spectral bands between 0.4 and 14.2 microns, with spatial resolution between 250 and 1000 meters. Modis-T has 32 bands with 10-15 nm bandwidths between 0.4 and 0.9 microns. Modis-T scans fore and aft +/- 50 degrees. Both instruments scan cross-track so as to provide daily (Modis-N) or once every two days (Modis-T) coverage at 705-km altitude. Both instruments are entering into the execution phases of their development in 1990. The bands of the Modis-N hve been chosen so as to provide key observations of land, ocean, and atmosphere parameters that will provide key data sets assisting in gaining an improved understanding of global processes.

Salomonson, Vincent V.↗
NASA NTRS1990

MODIS-N - Moderate Resolution Imaging Spectrometer-Nadir

The Moderate Resolution Imaging Spectrometer-Nadir (MODIS-N) for the Earth Observing System (EOS) is intended to provide daily global surveys for the atmosphere, the oceans, and the land. To achieve this capability, MODIS-N requires an at-least 2300-km swath width, and provides geometric-instantaneous-fields-of-view (GIFOVs) that are either 856 m, 428 m, or 214 m in size with reference to a 705 km satellite altitude. The 214 m GIFOV may or may not be used depending on total data rate impact assessments traded with science needs. To achieve the data for the multiplicity of science investigations MODIS-N provides nominally 36 spectral bands that are selected for specific locations and bandpasses in the spectral range from the visible to the long wave infrared. Another driver of this instrument combination is the need for long term spectral and radiometric calibration stability. Specific calibration capabilities are to be built into MODIS-N to achieve calibration knowledge over a 5 year operational life.

Weber, Richard R.↗
NASA NTRS1990

The Moderate Resolution Imaging Spectrometer-tilt (MODIS-T)

There will be several state-of-the-art spectrometers in operation on the NASA Polar Oribting Platform (NPOP-1) as part of the Earth Observing System. The Moderate Resolution Imaging Spectrometer (MODIS) will consist of two imaging spectroradiometric instruments, one nadir-viewing (MODIS-N) and the other tiltable (MODIS-T) for ocean observation and land bidirectional reflectance studies. The MODIS-T instrument is required to cover the wavelength range of 400 to 880 nm in approximately 15 steps, have less than 2.3 percent instrument-induced polarization, be calibrated to an absolute radiometric accuracy of at least 5 percent over the full dynamic range of the instrument, have a 1.1 kilometer square instantaneous field of view at nadir, and be capable of + or - 50-deg along-track tilt.

Magner, Thomas J.↗
NASA NTRS1991

Moderate resolution spectrophotometry of high redshift quasars

A uniform set of photometry and high signal-to-noise moderate resolution spectroscopy of 33 quasars with redshifts larger than 3.1 is presented. The sample consists of 17 newly discovered quasars (two with redshifts in excess of 4.4) and 16 sources drawn from the literature. The objects in this sample have r magnitudes between 17.4 and 21.4; their luminosities range from -28.8 to -24.9. Three of the 33 objects are broad absorption line quasars. A number of possible high redshift damped Ly-alpha systems were found.

Schneider, Donald P.↗
NASA NTRS1991

A time-dependent incompressible viscous BEM for moderate Reynolds numbers

The boundary element method is applied to transient viscous incompressible flow. The time-domain formulation allows a boundary-only solution for linear Stokes flow. For higher speed flows in which the nonlinear convective effects cannot be ignored, a volume integral must be retained. However, the introduction of reference velocities often limits the nonlinear region to the vicinity of obstacles or boundary surfaces. Additionally, the volume terms are rewritten to eliminate the need for the calculation of velocity gradients. A general purpose numerical implementation of this new formulation then produces a very attractive tool for engineering analysis. This implementation includes a Newton-Raphson algorithm, permitting accurate solutions up to the moderate Reynolds number range. Several numerical examples are provided to validate the present approach.

Dargush, G. F.↗
NASA NTRS1991

The moderate resolution imaging spectrometer: An EOS facility instrument candidate for application of data compression methods

The Moderate Resolution Imaging Spectrometer (MODIS) observing facility will operate on the Earth Observing System (EOS) in the late 1990's. It is estimated that this observing facility will produce over 200 gigabytes of data per day requiring a storage capability of just over 300 gigabytes per day. Archiving, browsing, and distributing the data associated with MODIS represents a rich opportunity for testing and applying both lossless and lossy data compression methods.

Salomonson, Vincent V.↗