Search NASA⌕ Search

SEARCH · Search NASA

Results for “Surface Physics”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

A model of diffuse radar scattering from Martian surface rocks

Two physically plausible surface rock-orientation models are presently used to characterize the depolarized component of diffuse radar energy scattering on Mars, and plots of scattering cross-section are derived as a function of Doppler shift. The spectral shapes thus modeled exhibit similarities to observed spectra; their magnitudes are generally within a factor of about 2 of measured values. While surface inhomogeneities could account for the degree of discrepancy, subsurface element scattering may also be implicated.

Calvin, Wendy M.↗
NASA NTRS1984

Contactless Measurement of Physical Properties

Surface tension and other properties determined from measurement of resonant frequency. Surface tension and other physical properties of molten and liquid samples excited at resonance measured by observing photographic or TV image and noting resonant frequency and rate of change. Technique used in normal gravity and low gravity in either vacuum or gaseous environment, where sample is positioned by electrostatic, acoustic, or magnetic forces.

Elleman, D. D.↗
NASA NTRS1990

Cophasing segmented mirrors with large surface errors using physical and geometrical ray-based techniques

Phasing an array with steep slopes and large surface errors, such as in NASA's Precision Segmented Reflector (PSR) Program for submillimeter astrophysics, is difficult using conventional optical techniques because the surface errors on the panels are large as compared with optical wavelengths. This paper extrapolates a procedure proposed by the Keck Observatory whereby physical optical techniques phase the edges of the panels, but with this technique they are phased with respect to a reference surface obtained from a high-quality central panel. A full-surface height-map is thereby obtained by integrating slope measurements, and full-surface phasing can be achieved using the modified and conventional Shack-Hartmann camera.

Manhart, Paul K.↗
NASA NTRS2010

Land Surface Emission Modeling to Support Physical Precipitation Retrievals

Land surface modeling and data assimilation can provide dynamic land surface state variables necessary to support physical precipitation retrieval algorithms over land. It is well-known that surface emission, particularly over the range of frequencies to be included in the Global Precipitation Measurement Mission (GPM), is sensitive to land surface states, including soil properties, vegetation type and greenness, soil moisture, surface temperature, and snow cover, density, and grain size. In order to investigate the robustness of both the land surface model states and the microwave emissivity and forward radiative transfer models, we have undertaken a multi-site investigation as part of the NASA Precipitation Measurement Missions (PMM) Land Surface Characterization. Working Group.

Peters-Lidard, Christina D.↗
NASA NTRS1989

Viking landing sites, remote-sensing observations, and physical properties of Martian surface materials

Consideration is given to the relations between the physical properties of the surface materials at Viking landing sites, the physical properties of other Martian surfaces inferred from radar observations from earth and thermal observations from orbit, and the geological processes that formed the materials and shaped the surfaces. The radar and thermal remote-sensing signatures of the landing site surface materials are estimated and compared with the thermal and radar measurements for the entire planet. It is shown that the surface materials at the landing sites are good analogs for the materials in most of the Martian equatorial regions.

Moore, Henry J.↗
NASA NTRS2007

Physical Retrieval of Surface Emissivity Spectrum from Hyperspectral Infrared Radiances

Retrieval of temperature, moisture profiles and surface skin temperature from hyperspectral infrared (IR) radiances requires spectral information about the surface emissivity. Using constant or inaccurate surface emissivities typically results in large retrieval errors, particularly over semi-arid or arid areas where the variation in emissivity spectrum is large both spectrally and spatially. In this study, a physically based algorithm has been developed to retrieve a hyperspectral IR emissivity spectrum simultaneously with the temperature and moisture profiles, as well as the surface skin temperature. To make the solution stable and efficient, the hyperspectral emissivity spectrum is represented by eigenvectors, derived from the laboratory measured hyperspectral emissivity database, in the retrieval process. Experience with AIRS (Atmospheric InfraRed Sounder) radiances shows that a simultaneous retrieval of the emissivity spectrum and the sounding improves the surface skin temperature as well as temperature and moisture profiles, particularly in the near surface layer.

Li, Jun↗
NASA NTRS1988

Physical properties of surface materials on Martian volcanoes: Dust-covered lava and ash

Remote sensing measurements provide information about the Martian surface at scales smaller than can be inferred from imaging data alone. Measurements of Martian volcanoes obtained at visual, infrared, and radar wavelengths are discussed in order to evaluate the physical properties. A related issue involves identifying possible ash deposits by distinctive or anomalous physical characteristics.

Zimbelman, James R.↗
NASA NTRS1987

A physical optics correction for backscattering from curved surfaces

The conventional physical optics (PO) approximation used to calculate the scattered fields from a conducting body leads to incorrect scattered fields even in the specular reflection region. This is true even when all other subdominant terms are assumed to be absent. The inaccuracy stems from the fact that the surface currents used in the PO approximation suddenly truncate at the shadow boundary of curved surfaces resulting in an erroneous contribution. Expressions for these shadow boundary (end point) contributions are presented in this paper. It is shown that if these end point contributions are substracted from the conventional PO results, one obtains a better representation of the true scattered field. For illustration, backscattered fields from various conducting bodies are computed using the corrected PO solution and are compared with the exact scattered fields.

Gupta, Inder J.↗