Search NASA⌕ Search

SEARCH · Search NASA

Results for “observability analysis”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

An Observation Data Driven Simulation and Analysis Framework for Early Stage C. elegans Embryogenesis

Recent developments in cutting-edge live microscopy and image analysis provide a unique opportunity to systematically investigate individual cell’s dynamics as well as simulation-based hypothesis testing. After a summary of data generation and analysis in the observation and modeling efforts related to C. elegans embryogenesis, we develop a systematic approach to model the basic behaviors of individual cells. Next, we present our ideas to model cell fate, division, and movement using 3D time-lapse images within an agent-based modeling framework. Then, we summarize preliminary result and discuss efforts in cell fate, division, and movement modeling. Finally, we discuss the ongoing efforts and future directions for C. elegans embryo modeling, including an inferred developmental landscape for cell fate, a quasi-equilibrium model for cell division, and multi-agent, deep reinforcement learning for cell movement.

3D live images↗
NASA NTRS1975

Analysis of spectrophotometric observations of Venus in the 3-4 micron region

Spectrophotometric data of Venus in the 3-4 micron region are analyzed in the context of current ideas concerning cloud properties. The results show that a homogeneous cloud model, using a unimodal particle size distribution compatible with the results of previous polarization studies, cannot satisfactorily explain the infrared observations. Assuming a composition of 75% H2SO4, agreement is possible if an upper layer of smaller particles is added to the homogeneous cloud. This inhomogeneous cloud structure, however, is not in agreement with the polarization results. Other models, involving bimodal particle size distributions, were also unsuccessful in explaining both sets of observations in a consistent manner.

Martonchik, J. V.↗
NASA NTRS1981

Analysis of IUE observations of CS in Comet Bradfield (1979 l)

The high resolution rotational band profiles were fitted with theoretical band profiles which are derived using a Boltzmann temperature of 70 K. A very rapid variation with heliocentric distance for the CS brightness was found. The implications of these results for models of the coma along with the origin of the CS species are discussed.

Rahe, J.↗
NASA NTRS1985

Analysis of experimental observations of electron temperatures in the near wake of a model in a laboratory-simulated solar wind plasma

In the present paper, the results are presented of the first laboratory experiments in a high-energy plasma which investigate the electron temperature Te in the body wake. A large number of Te samples in the very near- and near-wake regions downstream from a conducting body are employed. The obtained results are compared with the experimental findings of Oran et al. (1975), Stone (1981), and others. The findings are discussed in the more general context of theoretical studies and of other relevant considerations. Attention is also given to the possible relevance of the results to the maintenance of the nightside ionosphere of Venus, and suggestions are made regarding some specific spacecraft observations which should be carried out using the Pioneer Venus orbiter.

Intriligator, D. S.↗
NASA NTRS1985

Hyperion - Analysis of Voyager observations

Voyager imges of Hyperion are analyzed with respect to spin state, dimensions and shape, surface features, photometry, and colors. It is suggested that the two most important observations concerning Hyperion are the demonstration of the satellite's unusual spin state and the discovery of the apparent low density of large craters on the satellite's surface. A possible implication of such a reduced density of craters is that the last important fragmentation of Hyperion might have occurred near the end or after the period of initial heavy bombardment.

Thomas, P.↗
NASA NTRS1987

Titania's opposition effect - Analysis of Voyager observations

Voyager 2 obtained images of Titania over phase angles ranging from 0.8 to 150 deg and at sufficient resolution to investigate the photometric behavior of different surface units. The large, relatively narrow opposition surge detected from earth was confirmed and can be successfully modeled with Hapke's (1986) photometric theory. Opposition effects do not vary greatly between bright areas (craters and ejecta) and dark areas, but the brightness of the brighter areas decreases more slowly with increasing phase angle than that of the dark areas. Thus the fresher craters and their ejecta become less prominent in relation to the background as opposition is approached. This effect is best explained by a modest difference in single-scattering albedo.

Thomas, P. C.↗
NASA NTRS1988

An analysis of satellite observations of the O I EUV dayglow

Observations of the latitudinal variation of the 1356-A, 1304-A, and 989-A O I earth dayglow, obtained with the USAF STP78-1 satellite at solar maximum on March 21, 1979, are reported and compared with the predictions of thermospheric models and published laboratory measurements of electron-impact excitation cross sections. The results are presented in extensive tables and graphs and characterized in detail, with particular attention to the 1304-A solar flux and the 989-A branching ratio. The STP78-1 data (as well as simultaneous AE-E satellite measurements ) are shown to indicate exospheric temperatures that were 220-240-K higher, but varied significantly less with latitude, than those predicted by the MSIS-83 model (Hedin, 1983) for the day of the observations.

Link, R.↗
NASA NTRS1989

The mean ozone profile and its temperature sensitivity in the upper stratosphere and lower mesosphere - An analysis of LIMS observations

Multiple simultaneous LIMS (Limb Infrared Monitor of the Stratosphere) observations of both O3 and temperature T in the upper stratosphere and lower mesosphere are analyzed to derive O3-T correlations for comparisons with model calculations. The zonally averaged O3 profile is compared with results from a simplified photochemical model that assumes O3 to be in a photochemical steady state. The model profile is systematically lower than the observed profile. Key parameters are identified in which changes can systematically increase the O3 profile in both the stratosphere and the mesosphere. The LIMS-derived values for the sensitivity of O3 to changes in T are compared with equilibrium model calculations which include the T-driven opacity feedback effect on photodissociation rate constants. The theoretical O3 response to temperature perturbations is investigated. It is shown how the O3-T sensitivity coefficient is affected by zonal and vertical advection terms as well as by the photochemical coupling between O3 and T.

Froidevaux, Lucien↗
NASA NTRS1989

Analysis of coordinated observations of a giant stellar flare

Multi-wavelength observations of a giant flare on the star AD Leo were obtained with the 2.1 m and 0.9 m telescopes at McDonald Observatory and the International Ultraviolet Explorer satellite. The quality, spectral coverage, and time resolution of the data represented a major improvement over any published stellar flare data. Two theoretical, quantitative flare models were developed. Combining the models, the chromospheric emission model predictions in the hydrogen Balmer lines, Da II K, Mg II h + k and the optical continuum were compared to the observations, with the result that much of the gradual phase flare emission could be produced by the x ray and conductive heated atmospheres. The models lend insight into the impulsive phase flare emission, but do not reproduce it. Soft x ray and conductive heating of the chromosphere is a natural consequence of the coronal temperatures that have been observed during the gradual phase of flares on the sun and on M dwarf stars. The improved flare observations and quantitative flare models presented here show that these heating mechanisms can produce atmospheres whose emission matches many of the observed stellar flare features.

Lambert, David L.↗
NASA NTRS1990

An analysis of lidar observations of polar stratospheric clouds

Lidar observations by Browell et al. (1990) are interpreted using single scattering calculations for nonspherical particles and aerosol microphysical calculations. Many of the lidar observations are consistent with particles containing 10 ppbv of condensed nitric acid vapor and an equivalent mass of water. The lidar observations of these Type 1 clouds identify two subtypes, whose properties are deduced. Type 1b particles are spherical, or nearly spherical, and typically have radii near 0.5 micron; Type 1a particles are not spherical, and have a spherical volume equivalent radius exceeding 1.0 micron. Several factors may cause variations in the size of the particles. The most significant factors are the cooling rate and the degree to which the air parcels cool below the condensation point. Specific examples in which cooling rate and cooling point may have led to variations in particle size are found in the Browell et al. (1990) data set. Condensation of 1 ppmm of water or less is quantitatively sufficient to account for the magnitude of the lidar backscatter observed from water ice clouds. The ice particles are not spherical in shape. The sizes of particles in water ice clouds cannot be determined because they are much larger than the wavelength of the lidar.

Toon, Owen B.↗
NASA NTRS1990

Vertical motions in the Uranian atmosphere - An analysis of radio observations

The present, 6-cm radio map of Uranus indicates latitudinal features which may be due to vertical motions of the atmosphere. It appears in light of Voyager IR measurements as well as previously obtained radio data that these large-scale vertical motions, which have not undergone significant changes over the course of 8 years, extend from the 0.1- to the 45-bar levels; this span corresponds to a height of the order of 250 km. The latitudinal structures are believed to be primarily caused by horizontal variations of absorber abundances.

Hofstadter, Mark D.↗
NASA NTRS1992

Assessing deforestation and habitat fragmentation in Uganda using satellite observations and fractal analysis

The MSS, SPOT, and AVHRR imagery of Ugandan forests were analyzed to assess the information content related to deforestation and tropical habitat fragmentation, focusing primarily on the Kibale and Mabira Forests. Analysis of actual and simulated AVHRR imagery showed that it might be possible to monitor major changes in forest extent with the relatively coarse spatial resolution of AVHRR imagery (about 1 km) provided ancillary data were available. The fractal dimension of the forest edges, measured with the Landsat and SPOT imagery, was consistently about 1.7 or 1.8. This high fractal dimension was due to the coplex pattern of clearings, remnant forest stands, and jagged forest edges caused by repeated human encroachment over centuries.

Hlavka, Christine A.↗
NASA NTRS1994

Determination of the atmospheric structure of the BO star companion of SMC X-1 by analysis of Ginga observations

The x-ray phenomena of the binary system SMC X-1/Sk 160, observed with the Ginga and ROSAT x-ray observatories, are compared with computed phenomena derived from a three dimensional hydrodynamical model of the stellar wind perturbed by x-ray heating and ionization which is described in the accompanying paper. In the model the BOI primary star has a line-driven stellar wind in the region of the x-ray shadow and a thermal wind in the region heated by x-rays. We find general agreement between the observed and predicted x-ray spectra throughout the binary orbit cycle, including the extended, variable, and asymmetric eclipse transitions and the period of deep eclipse.

Clark, George W.↗
NASA NTRS1996

Analysis of LAC Observations of Clusters of Galaxies and Supernova Remnants

The following publications are included and serve as the final report: The X-ray Spectrum of Abell 665; Clusters of Galaxies; Ginga Observation of an Oxygen-rich Supernova Remnant; Ginga Observations of the Coma Cluster and Studies of the Spatial Distribution of Iron; A Measurement of the Hubble Constant from the X-ray Properties and the Sunyaev-Zel'dovich Effect of Abell 2218; Non-polytropic Model for the Coma Cluster; and Abundance Gradients in Cooling Flow Clusters: Ginga LAC (Large Area Counter) and Einstein SSS (Solid State Spectrometer) Spectra of A496, A1795, A2142, and A2199.

Hughes, J.↗