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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Quantifying parameters influencing the spacing of geostationary satellites.

Parameters affecting satellite spacing must be investigated to fully exploit the limited capacity of the geostationary orbit. The usefulness of laboratory experiments, analytic methods, and space environment experiments in quantifying these factors is discussed. It is concluded that space environment experiments are required to evaluate the effects of operationally related parameters including antenna gain patterns, polarization, and antenna instabilities. A unique method of measuring the time-variant effects of the earth station antenna characteristics on satellite spacing is described as a possible space environment experiment. The proposed experiment uses a single satellite to obtain the required data.

Henry, V. F.↗
NASA NTRS1993

Retrieval of cirrus cloud parameters from satellite observations: Evaluation from field experiments

Knowledge on cirrus clouds gained from experiments involving in situ observations in close coordination with ground and aircraft based remote sensing, as well as satellite observations and other conventional observations such as rawinsondes, is presented. The methodologies used to retrieve cirrus cloud parameters from satellite observations are reviewed, results from field campaigns are discussed in terms of these methods, and prospects for satellite remote sensing of cirrus are discussed.

Starr, David OC.↗
NASA NTRS1990

A comparison of ISCCP and FIRE satellite cloud parameters

One of the goals of the First ISCCP Regional Experiment (FIRE) is the quantification of the uncertainties in the cloud parameter products derived by the International Satellite Cloud Climatology Project (ISCCP). This validation effort has many facets including sensitivity analyses and comparisons to similar data or theoretical results with known accuracies. The FIRE provides cloud-truth data at particular points or along particular lines from surface and aircraft measurement systems. Relating these data to the larger, area-averaged ISCCP results requires intermediate steps using higher resolution satellite data analyses. Errors in the cloud products derived with a particular method can be determined by performing analyses of high resolution satellite data over the area surrounding the point or line measurement. This same analysis technique may then be used to derive cloud parameters over a larger area containing similar cloud fields. It is assumed that the uncertainties found for the small scale analyses are the same for the large scale so that the method has been calibrated for the particular cloud type; i.e., its accuracy is known. Differences between the large scale results using the ISCCP technique and the calibrated method can be computed and used to determine if any significant biases or rms errors occur in the ISCCP results. Selected ISCCP results are compared to cloud parameters derived using the hybrid bispectral threshold method over the FIRE IFO and extended observation areas.

Gibson, Gary G.↗
NASA NTRS1984

A model for the estimation of the surface fluxes of momentum, heat and moisture of the cloud topped marine atmospheric boundary layer from satellite measurable parameters

A model is developed for the estimation of the surface fluxes of momentum, heat, and moisture of the cloud topped marine atmospheric boundary layer by use of satellite remotely sensed parameters. The parameters chosen for the problem are the integrated liquid water content, q sub li, the integrated water vapor content, q sub vi, the cloud top temperature, and either a measure of the 10 meter neutral wind speed or the friction velocity at the surface. Under the assumption of a horizontally homogeneous, well-mixed boundary layer, the model calculates the equivalent potential temperature and total water profiles of the boundary layer along with the boundary layer height from inputs of q sub li, q sub vi, and cloud top temperature. These values, along with the 10m neutral wind speed or friction velocity and the sea surface temperature are then used to estimate the surface fluxes. The development of a scheme to parameterize the integrated water vapor outside of the boundary layer for the cases of cold air outbreak and California coastal stratus is presented.

Allison, D. E.↗
NASA NTRS1986

Some background about satellites

Four tables of planetary and satellite data are presented which list satellite discoveries, planetary parameters, satellite orbits, and satellite physical properties respectively. A scheme for classifying the satellites is provided and it is noted that most known moons fall into three general classes: regular satellites, collisional shards, and irregular satellites. Satellite processes are outlined with attention given to origins, dynamical and thermal evolution, surface processes, and composition and cratering. Background material is provided for each family of satellites.

Burns, Joseph A.↗
NASA NTRS2021

Retrieval of Stratospheric Aerosol Size Distribution Parameters Using Satellite Solar Occultation Measurements at Three Wavelengths

In this work, a novel approach for the determination of the particle size distribution (PSD) parameters of stratospheric sulfate aerosols is presented. For this, ratios of extinction coefficients obtained from SAGE III/ISS (Stratospheric Aerosol and Gas Experiment III on the International Space Station) solar occultation measurements at 449, 756 and 1544 nm were used to retrieve the mode width and median radius of a size distribution assumed to be monomodal lognormal. The estimated errors at the peak of the stratospheric aerosol layer, on average, lie between 20% and 25% for the median radius and 5% and 7% for the mode width. The results are consistent in magnitude with other retrieval results from the literature, but a robust comparison is difficult, mainly because of differences in temporal and spatial coverage. Other quantities like number density and effective radius were also calculated. A major advantage of the described method over other retrieval techniques is that both the median radius and the mode width can be retrieved simultaneously, without having to assume one of them. This is possible due to the broad wavelength spectrum covered by the SAGE III/ISS measurements. Also, the presented method – being based on the analysis of three wavelengths – allows unique solutions for the retrieval of PSD parameters for almost all of the observed extinction spectra, which is not the case when using only two spectral channels. In addition, the extinction coefficients from SAGE III/ISS solar occultation measurements, on which the retrieval is based, are calculated without a priori assumptions about the PSD. For those reasons, the data produced with the presented retrieval technique may be a valuable contribution for a better understanding of the variability of stratospheric aerosol size distributions, e.g. after volcanic eruptions. While this study focuses on describing the retrieval method, and a future study will discuss the PSD parameter data set produced in depth, some exemplary results for background conditions in June 2017 are shown.

Felix Wrana↗
NASA NTRS1987

The correspondence of surface climate parameters with satellite and terrain data

One of the goals of the research was to develop a ground sampling stragegy for calibrating remotely sensed measurements of surface climate parameters. The initial sampling strategy involved the stratification of the terrain based on important ancillary surface variables such as slope, exposure, insolation, geology, drainage, fire history, etc. For a spatially heterogeneous population, sampling error is reduced and efficiency increased by stratification of the landscape into more homogeneous sub-areas and by employing periodic random spacing of samples. These concepts were applied in the initial stratification of the study site for the purpose of locating and allocating instrumentation.

Dozier, Jeff↗
NASA NTRS1988

Uranus satellites - Hapke parameters from Voyager disk-integrated photometry

An attempt is presently made to obtain improved determinations of the geometric albedos and phase integrals of Miranda, Ariel, Umbriel, Titania, and Oberon, by fitting Hapke's (1981, 1984, 1986) photometric theory to Voyager whole-disk observations of these satellites. It is analytically established that while Umbriel, Titania and Oberon have large-scale roughness comparable to that of the earth's moon, Ariel is significantly rougher. While the particle single scattering albedo is strikingly different among the satellites, the degrees of regolith particle backscattering are very similar.

Helfenstein, Paul↗
NASA NTRS1993

Age discrimination among eruptives of Menengai Caldera, Kenya, using vegetation parameters from satellite imagery

Results are presented of an investigation to determine the degree to which digitally processed Landsat TM imagery can be used to discriminate among vegetated lava flows of different ages in the Menengai Caldera, Kenya. A selective series of five images, consisting of a color-coded Landsat 5 classification and four color composites, are compared with geologic maps. The most recent of more than 70 postcaldera flows within the caldera are trachytes, which are variably covered by shrubs and subsidiary grasses. Soil development evolves as a function of time, and as such supports a changing plant community. Progressively older flows exhibit the increasing dominance of grasses over bushes. The Landsat images correlated well with geologic maps, but the two mapped age classes could be further subdivided on the basis of different vegetation communities. It is concluded that field maps can be modified, and in some cases corrected by use of such imagery, and that digitally enhanced Landsat imagery can be a useful aid to field mapping in similar terrains.

Blodget, Herbert W.↗
NASA NTRS1993

Comparison of radiation and cloud parameters derived from satellite and aircraft measurements during FIRE 2 cirrus IFO

Meteorological satellite instrument pixel sizes are often much greater than the individual cloud elements in a given scene. Partially cloud-filled pixels can be misinterpreted in many analysis schemes because the techniques usually assume that all of the cloudy pixels are cloud filled. Coincident Landsat and Geostationary Operational Environmental Satellite (GOES) data and degraded-resolution Landsat data were used to study the effects of both sensor resolution and analysis techniques on satellite-derived cloud parameters. While extremely valuable for advancing the understanding of these effects, these previous studies were relatively limited in the number of cloud conditions that were observed and by the limited viewing and illumination conditions. During the First ISCCP Regional Experiment (FIRE) Phase 2 (13 Nov. - 7 Dec. 1991), the NASA ER-2 made several flights over a wide range of cloud fields and backgrounds with several high resolution sensors useful for a variety of purposes including serving as ground truth for satellite-based cloud retrievals. This paper takes a first look at utilizing the ER-2 for validating cloud parameters derived from GOES and NOAA-11 Advanced Very High Resolution Radiometer (AVHRR) data.

Heck, Patrick W.↗
NASA NTRS1978

Galilean satellites - Analysis of photometric eclipses

The excellent series of photometric eclipses of the Galilean satellites observed at Harvard from 1878 to 1903, which formed the basis for Sampson's study of the Galilean satellites, have been combined with the relatively few available post-1903 photometric eclipse observations in order to evaluate the satellite parameters which occur in the new theory of motion of the satellites. After obtaining values for the epsilon-beta parameters, the mutual eclipses and occultations observed in 1973 are compared with the new theory in order to assess the degradation which might occur in the 84 years which have elapsed since the mean epoch of the photometric eclipses. The results indicate that the new theory satisfactorily can predict ephemeris positions of the Galilean satellites over spans of nearly a century and that it will be a useful tool for analyzing future observations.

Lieske, J. H.↗
NASA NTRS2005

Bulk Surface Momentum Parameters for Satellite-Derived Vegetation Fields

The bulk aerodynamic parameters associated with the absorption of surface momentum by vegetated landscapes are theoretically estimated within the context of Raupach's roughness sublayer formulation. The parameters include the bulk plant drag coefficient, maximum u*/U(sub h), sheltering coefficient, and canopy area density at onset of sheltering. Parameters are estimated for the four principal IGBP land cover classes within the U.S. Southern Great Plains: evergreen needleleaf forests, grasslands, croplands, and open shrublands. The estimation approach applies the Method of Moments to roughness data from several international field experiments and other published sources. The results provide the necessary land surface parameters for satellite-based estimation of momentum aerodynamic roughness length and zero-plane displacement height for seasonally variable vegetation fields employed in most terrestrial and atmospheric simulation models used today. Construction of sample displacement and roughness maps over the Southern United States using MODIS land products demonstrates the potential of this approach for regional to global applications.

Jasinski, Michael F.↗
NASA NTRS1985

Retrieval of cloud cover parameters from multispectral satellite images

A technique is described for extracting cloud cover parameters from multispectral satellite radiometric measurements. Utilizing three channels from the AVHRR (Advanced Very High Resolution Radiometer) on NOAA polar orbiting satellites, it is shown that one can retrieve four parameters for each pixel: cloud fraction within the FOV, optical thickness, cloud-top temperature and a microphysical model parameter. The last parameter is an index representing the properties of the cloud particle and is determined primarily by the radiance at 3.7 microns. The other three parameters are extracted from the visible and 11 micron infrared radiances, utilizing the information contained in the two-dimensional scatter plot of the measured radiances. The solution is essentially one in which the distributions of optical thickness and cloud-top temperature are maximally clustered for each region, with cloud fraction for each pixel adjusted to achieve maximal clustering.

Arking, A.↗