SEARCH · Search NASA
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.
Various studies concerning differing aspects of the North Atlantic are presented. The three major topics under which the works are classified include: (1) oceanography; (2) paleoclimate; and (3) ocean, ice and climate modeling.
Various papers on remote sensing are presented. The general topics addressed include: remote sensing of the biosphere, geophysical inversion, science and archaeology, image processing, sensing the atmosphere with microwaves, analysis of scattering for remote sensing, advanced sensors and technology, archaeology, data processing, fiber optics, Landsat-4 and TM. Also discussed are: remote sensing and microwave instrumentation, soil moisture and hydrology, measurement techniques for ocean surface waves, geological remote sensing, radar millimeter wave propagation through the atmosphere, and remote sensing in planetary science, geophysics, hydrology, oceanography, and surface vegetation.
Electromagnetic bias, the small difference that exists between the radar measured mean sea level and the geometric mean sea level is an important issue in high precision satellite altimetry. Present day satellite altimetry has achieved, with SEASAT-1, a precision of 5 cm rms in the range measurement. Future altimeter designs are expected to improve the range measurement precision to cm rms. In order to exploit the capability of these precise radar altimeters are marine geodesy and oceanography, it is necessary to understand and account for all of the known biases in the range measurement. The electromagnetic bias or the EM bias, which has been attributed to the observed fact that ocean wave troughs tend to be better reflectors of nadir viewing microwave radar energy than ocean wave crests, can be observed with high resolution airborne radar. This report presents the results of the EM bias measurements made by NRL using an airborne radar altimeter operating at 10 GHz with a 1 ns range resolution. Data were taken for various sea states and wind conditions. The experimental results are compared with current theories.
A series of three workshops was held between January 1983 and February 1984 to assess the current status of global sea surface temperature (SST) measurement from space. Workshop participants included sensor scientists, radiative transfer specialists, and users of SST data in the disciplines of oceanography and climate. Data from four satellite sensors (three infrared and one microwave) were evaluated by direct comparison with each other and with data from ships, XBTs, and buoys. The satellite data showed good agreement in a global rms sense (about 0.5-1.0 C), but several anomalous regional biases were also observed. The nature of these biases and techniques for their removal require further study.
Against background of spacecraft and in situ measurements, participants at the JPL workshops sought to review the sensor performance, understand the different SSt retrieval algorithms, evaluate the sensor SST accuracies, and discuss directions for future sensor development. The issue of utilization of satellite SSTs in climate, air sea interaction, and mesoscale oceanography studies was not the main focus of the workshops, but did have a bearing on the recommendations that arose from the discussions. More date were available for analysis with the acquisition of AVHRR (MCSST), HIRS/MSU, and VAS data sets. In Workshop 3 the acquisition and analysis fo data were completed, recommendations for future research and sensor development were discussed, and plans were made for eventual publication of results from the workshop series in the open literature.
An assessment of the status of research using Global Weather Experiment (GWE) data and of the progress in meeting the objectives of the GWE, i.e., better knowledge and understanding of the atmosphere in order to provide more useful weather prediction services. Volume Two consists of a compilation of the papers presented during the workshop. These cover studies that addressed GWE research objectives and utilized GWE information. The titles in Part 2 of this volume include General Circulation Planetary Waves, Interhemispheric, Cross-Equatorial Exchange, Global Aspects of Monsoons, Midlatitude-Tropical Interactions During Monsoons, Stratosphere, Southern Hemisphere, Parameterization, Design of Observations, Oceanography, Future Possibilities, Research Gaps, with an Appendix.
An objective analysis technique has been developed to extrapolate tidal amplitudes and phases over entire ocean basins using existing gauge data and the altimetric measurements which are now beginning to be provided by satellite oceanography. The technique was previously tested in the Lake Superior basin. The method has now been developed and applied in the Atlantic-Indian ocean basins using a 6 deg x 6 deg grid to test its essential features. The functions used in the interpolation are the eigenfunctions of the velocity potential (Proudman functions) which are computed numerically from a knowledge of the basin's bottom topography, the horizontal plan form and the necessary boundary conditions. These functions are characteristic of the particular basin. The gravitational normal modes of the basin are computed as part of the investigation, they are used to obtain the theoretical forced solutions for the tidal constituents, the latter provide the simulated data for the testing of the method and serve as a guide in choosing the most energetic modes for the objective analysis. The results of the objective analysis of the M2 and K1 tidal constituents indicate the possibility of recovering the tidal signal with a degree of accuracy well within the error bounds of present day satellite techniques.
In October 1984, SIR-B obtained digital image data of about 6.5 million km2 of the Earth's surface. The coverage is mostly of selected experimental test sites located between latitudes 60 deg north and 60 deg south. Programmed adjustments made to the look angle of the steerable radar antenna and to the flight attitude of the shuttle during the mission permitted collection of multiple-incidence-angle coverage or extended mapping coverage as required for the experiments. The SIR-B images included here are representative of the coverage obtained for scientific studies in geology, cartography, hydrology, vegetation cover, and oceanography. The relations between radar backscatter and incidence angle for discriminating various types of surfaces, and the use of multiple-incidence-angle SIR-B images for stereo measurement and viewing, are illustrated with examples. Interpretation of the images is facilitated by corresponding images or photographs obtained by different sensors or by sketch maps or diagrams.
A new oceanographic instrument to measure underwater optical, biological and physical properties simultaneously has been built and used extensively at sea. The Bio-Optical Profiling System (BOPS) was designed for the rapid acquisition of data to accommodate shipboard 'synoptic' sampling strategies, often in conjunction with concurrent aircraft and satellite sensors. The data rates and associated quantity of data from the BOPS are some orders of magnitude larger than those traditionally encountered in optical oceanography. The rapid acquisition of optical data in a wide range of environmental conditions requires new methodologies in ocean optical data analysis.
In the present assessment of the contributions of optical earth resources remote sensing in the 0.4-15.0 micron region, attention is given to underlying principles, applications to scientific disciplines such as geology, hydrology and oceanography, the recent development history of the requisite sensors, and sensor development trends. Development status characterizations are given for thematic mapping, modular optoelectronic multispectral scanning, the telescope/CCD 'SPOT' program of France, the thermal IR multispectral scanner for mineral signature identification, airborne imaging spectrometry, and the Advanced Visible and IR Imaging Spectrometer that is nearing deployment. Technology development trends and the capabilities they portend are projected.
Spaceborne microwave remote sensors provide perspectives of the earth surface and atmosphere which are of unique value in scientific studies of geomorphology, oceanic waves and topography, atmospheric water vapor and temperatures, vegetation classification and stress, ice types and dynamics, and hydrological characteristics. Microwave radars and radiometers offer enhanced sensitivities to the geometrical characteristics of the earth's surface and its cover, to water in all its forms - soil and vegetation moisture, ice, wetlands, oceans, and atmospheric water vapor, and can provide high-resolution imagery of the earth's surface independent of cloud cover or sun angle. A brief review of the historical development and principles of active and passive microwave remote sensing is presented, with emphasis on the unique characteristics of the information obtainable in the microwave spectrum and the value of this information to global geoscientific studies. Various spaceborne microwave remote sensors are described, with applications to geology, planetology, oceanography, glaciology, land biology, meteorology, and hydrology. A discussion of future microwave remote sensor technological developments and challenges is presented, along with a summary of future missions being planned by several countries.
A semiweekly sampling program at the Scripps Institution of Oceanography Pier was begun in 1983 during an El Nino event. Microplankton data for March to November 1983 show a temporal sequence of species assemblages of the 24 important taxa, with a residence time of 1 to 4 weeks. From March to early September, the assemblages consisted of typial neritic taxa. From mid-September to mid-November, the presence of oceanic warm-wave species was associated with positive temperature anomalies characteristic of the El Nino condition. During the period studied numerical abundances were low.
Preliminary results of analyzing digital radar imagery data obtained by the SIR-B aboard the Space Shuttle Challenger STS 41-G are presented. The data cover 5 million square kilometers of the earth surface between 57 deg north and south latitudes. Radar imagery of the same target at different incidence angles was used to classify surfaces by their backscatter response as a function of incidence angle. The SIR-B proved to be useful for collecting multiple incidence angle data sets over a broad range of targets, providing information in the areas of geology, archeology, forestry, agriculture, oceanography, geography, and hydrology. The analysis is also used to optimize radar parameters such as look angle for future missions.
SIR-C is a continuation of the Shuttle Imaging Radar (SIR) series of synthetic aperture radar (SAR) imaging systems flown by the Jet Propulsion Laboratory aboard the Space Shuttle. SIR-A, flown in 1981, showed that SAR can be a useful remote sensing tool in the fields of geology, hydrology, and oceanography. SIR-B added the capability of moving the radar's antenna in 1984, showing that multiple incidence angle images add materially to the usefulness of SAR. SIR-C will add the dimensions of wavelength and polarization, providing the most powerful system ever flown for SAR scientific studies of the earth.
Data collected with the Shuttle Imaging Radar-B (SIR-B) on the October 5, 1985 Shuttle mission are discussed. The design and capabilities of the sensor which operates in a fixed illumination geometry and has incidence angles between 15 and 60 deg with 1 deg increments are described. Problems encountered with the SIR-B during the mission are examined. the The radar stereo imaging capability of the sensor was verified and three-dimensional images of the earth surface were obtained. The oceanography experiments provided significant data on ocean wave and internal wave patterns, oil spills, and ice zones. The geological images revealed that the sensor can evaluate penetration effect in dry soil from buried receivers and the existence of subsurface dry channels in the Egyptian desert was validated. The use of multiincidence angle imaging to classify terrain units and derive vegetation maps and the development of terrain maps are confirmed.
The application of spaceborne imaging radar data to polar oceanography and sea ice is explored. Several problems come to mind which are presently ripe with ideas and models, but are in need of new data, SAR data, for any progress to be made. These are the study of the ice mass balance, the ice momentum balance, and the circulation of the Arctic Ocean. These problems are described along with the data which is applicable to them and can be extracted from SAR imagery. Some uses are discussed of these data to explore mesoscale processes which affect the oceans and ice cover.
This report is the Fourth Annual Summary of the Research Program of the Geodynamics Branch. The branch is located within the Laboratory for Terrestrial Physics of the Space and Earth Sciences Directorate of the Goddard Space Flight Center. The research activities of the branch staff cover a broad spectrum of geoscience disciplines including: tectonophysics, space geodesy, geopotential field modeling, and dynamic oceanography. The NASA programs which are supported by the work described in this document include the Geodynamics and Ocean Programs, the Crustal Dynamics Project and the proposed Ocean Topography Experiment (TOPEX). The reports highlight the investigations conducted by the Geodynamics Branch staff during calendar year 1985. The individual papers are grouped into chapters on Crustal Movements and Solid Earth Dynamics, Gravity Field Modeling and Sensing Techniques, and Sea Surface Topography. Further information on the activities of the branch or the particular research efforts described herein can be obtained through the branch office or from individual staff members.
The Shuttle Imaging Radar-C (SIR-C) mission will yield new and advanced scientific studies of the Earth. SIR-C will be the first instrument to simultaneously acquire images at L-band and C-band with HH, VV, HV, or VH polarizations, as well as images of the phase difference between HH and VV polarizations. These data will be digitally encoded and recorded using onboard high-density digital tape recorders and will later be digitally processed into images using the JPL Advanced Digital SAR Processor. SIR-C geologic studies include cold-region geomorphology, fluvial geomorphology, rock weathering and erosional processes, tectonics and geologic boundaries, geobotany, and radar stereogrammetry. Hydrology investigations cover arid, humid, wetland, snow-covered, and high-latitude regions. Additionally, SIR-C will provide the data to identify and map vegetation types, interpret landscape patterns and processes, assess the biophysical properties of plant canopies, and determine the degree of radar penetration of plant canopies. In oceanography, SIR-C will provide the information necessary to: forecast ocean directional wave spectra; better understand internal wave-current interactions; study the relationship of ocean-bottom features to surface expressions and the correlation of wind signatures to radar backscatter; and detect current-system boundaries, oceanic fronts, and mesoscale eddies. And, as the first spaceborne SAR with multi-frequency, multipolarization imaging capabilities, whole new areas of glaciology will be opened for study when SIR-C is flown in a polar orbit.