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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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NASA NTRS1975

A SEASAT-A synthetic aperture imaging radar system

The SEASAT, a synthetic aperture imaging radar system is the first radar system of its kind designed for the study of ocean wave patterns from orbit. The basic requirement of this system is to generate continuous radar imagery with a 100 km swath with 25m resolution from an orbital altitude of 800 km. These requirements impose unique system design problems. The end to end data system described including interactions of the spacecraft, antenna, sensor, telemetry link, and data processor. The synthetic aperture radar system generates a large quantity of data requiring the use of an analog link with stable local oscillator encoding. The problems associated in telemetering the radar information with sufficient fidelity to synthesize an image on the ground is described as well as the selected solutions to the problems.

Jordan, R. L.↗
NASA NTRS1974

Satellite observations of weather and climate

The SEASAT-A program is viewed as a new way to obtain atmospheric observations for weather and climatic studies in the framework of the Global Atmospheric Research Program (GARP). Total information derived from SEASAT-A sensor package provides a synoptic picture of the upper parts of the world's oceans as a prerequisite to the development of dynamic ocean models and combined ocean/atmospheric models for weather forecasting requirements.

Kellogg, W. W.↗
NASA NTRS1975

On-board data management study for EOPAP

The requirements, implementation techniques, and mission analysis associated with on-board data management for EOPAP were studied. SEASAT-A was used as a baseline, and the storage requirements, data rates, and information extraction requirements were investigated for each of the following proposed SEASAT sensors: a short pulse 13.9 GHz radar, a long pulse 13.9 GHz radar, a synthetic aperture radar, a multispectral passive microwave radiometer facility, and an infrared/visible very high resolution radiometer (VHRR). Rate distortion theory was applied to determine theoretical minimum data rates and compared with the rates required by practical techniques. It was concluded that practical techniques can be used which approach the theoretically optimum based upon an empirically determined source random process model. The results of the preceding investigations were used to recommend an on-board data management system for (1) data compression through information extraction, optimal noiseless coding, source coding with distortion, data buffering, and data selection under command or as a function of data activity, (2) for command handling, (3) for spacecraft operation and control, and (4) for experiment operation and monitoring.

Davisson, L. D.↗
NASA NTRS1975

An operational satellite scatterometer for wind vector measurements over the ocean

Performance requirements and design characteristics of a microwave scatterometer wind sensor for measuring surface winds over the oceans on a global basis are described. Scatterometer specifications are developed from user requirements of wind vector measurement range and accuracy, swath width, resolution cell size and measurement grid spacing. A detailed analysis is performed for a baseline fan-beam scatterometer design, and its performance capabilities for meeting the SeaSat-A user requirements. Various modes of operation are discussed which will allow the resolution of questions concerning the effects of sea state on the scatterometer wind sensing ability and to verify design boundaries of the instrument.

Grantham, W. L.↗
NASA NTRS1975

The nature of multiple solutions for surface wind speed over the oceans from scatterometer measurements

The satellite SEASAT-A will carry a radar scatterometer in order to measure microwave backscatter from the sea surface. From pairs of radar measurements at angles separated by 90 deg in azimuth the surface wind speed and direction may be inferred, though not uniquely. The character of the solutions for wind speed and direction is displayed, as well as the nature of the ambiguities of these solutions. An economical procedure for handling such data is described, plus a criterion for the need for conventional (surface) data in order to resolve the ambiguities of solutions.

Price, J. C.↗
NASA NTRS1975

Microwave scattering from the ocean surface

This paper is a review of current aircraft and satellite microwave remote sensing programs concerned with the measurement of ocean wave and surface wind conditions. These particular measurements have been identified by the user community as offering significant economic and technological benefits. Active microwave remote sensing techniques for these applications have been described theoretically and verified experimentally. The results of recent aircraft and satellite experimental programs are presented herein along with plans for the SeaSat-A Satellite Scatterometer.

Jones, W. L.↗
NASA NTRS1974

Comments on potential Seasat applications

Potential benefits of expected SEASAT-A capabilities include oceanographic support of industrial and commercial activities, rapid dissemination of data in forecast-type activities, greater monitoring abilities at better spatial resolutions, and long time operational data gathering.

Baer, L.↗
NASA NTRS1974

Measurements of transient currents in mid-ocean by altimetry

Evidence is put forward that SEASAT-A altimetry will be accurate enough to provide interesting information on transient currents in mid-ocean areas. The discussion rests on the assumption that the observed currents are largely in geostrophic equilibrium rather than due to local winds. Surface current velocities are determined by integrating satellite navigation positions and dead reckoning data using an automatic log attached to a vessel hull.

Bryan, K.↗
NASA NTRS1974

Seasat and polar ice

The instrument package for SEASAT-A possesses three tools that could give data greatly needed in ice cap research: the Compressed Pulse Radar Altimeter (CPRA), the Coherent Imaging Radar (CIR), and the Scanning Multifrequency Microwave Radiometer (SMMR). Certain problems that can be studied with each sensor are discussed.

Campbell, W. J.↗
NASA NTRS1974

Civil and scientific applications of the geoid

SEASAT-A can be used for determining the geoid to much higher accuracy on a world wide basis and in a relatively short time. Two basic objectives can be considered: (1) determination of the geoid to at least 1 meter. This accuracy will satisfy most geodetic requirements for applications purposes; and (2) determination of the geoid to better than 1-meter an oceanographic objective required for measurement of sea surface topography and sea slope, quasi-stationary departure from the geoid, ocean circulation, air and sea interaction, etc. The geodesy objective in this case will be to define a reference equipotential surface as a means by which the oceanographic requirements can be achieved.

Mourad, A. G.↗
NASA NTRS1974

On the remote sensing of directional wave spectra and surface winds

The potential benefits of remote SEASAT-A satellite sensing of wind directional wave spectra by active microwave systems are elaborated. It is shown that a combined effort which uses supplemental satellite information in numerical forecasting and hindcasting schemes upgrades the accuracy of existing forecasting methods of an order of magnitude.

Shemdin, O. H.↗
NASA NTRS1974

Microwave measurement of sea surface temperature

SEASAT-A microwave radiometry is considered for scientific studies related to sea surface temperature measurements. Its limited swath width negates certain studies at angles greater than about 30 deg from nadir. Symmetrical scans appear best for operational experiments. It is recommended that a mode of scan be incorporated which permits data to be collected from nadir up to 11 55-60 deg from nadir, even if a symmetrical scan is necessary.

Sherman, J. W., III↗
NASA NTRS1974

Seasat and floating ice

Data collected by SEASAT would be useful in developing predictive physical models for the drift and deformation of sea ice, for estimating the heat budget of the polar seas, for the optimum routing of shipping through pack ice areas, for the design of both offshore structures and shipping capable of surviving in heavy pack ice, and for the tracking of large icebergs and ice islands. The instrument package for SEASAT-A is particularly useful for studying sea ice in that the Coherent Imaging Radar (CIR), the Scanning Multifrequency Microwave Radiometer (SMMR) and the Compressed Pulse Radar Altimeter (CPRA) are not limited by the presence of clouds.

Weeks, W. F.↗
NASA NTRS1974

The Earth and Ocean Physics Applications Program (EOPAP). Ocean dynamics program

SEASAT-A is a research oriented program consisting of a spacecraft, precision ground tracking systems, and data processing and modelling capabilities that address both scientific and application programs problems in ocean surface dynamics for the EOPAP program. An array of active radar and passive microwave and infrared instruments allows for quantitative measurements of oceanic, atmospheric, and geodetic parameters under stormy wind and wave conditions, as well as over regions lying under a cloud cover.

Apel, J. R.↗
NASA NTRS1976

The theory and applications of ocean wave measuring systems at and below the sea surface, on the land, from aircraft, and from spacecraft

Methods for measuring and analyzing ocean waves are described, including those presently in use on spacecraft and planned for SEASAT-A. Potential difficulties with synthetic aperture systems for a spacecraft are described and an alternate design is suggested. The different methods can yield different kinds of spectra and other kinds of imagery. Ways to compare different kinds of data are given. The scientific and practical applications of data from spacecraft are given.

Pierson, W. J.↗
NASA NTRS1975

Coastal data accumulation potentials for operational systems using airplanes

Potential users of SEASAT for remote sensing of coastal zone phenomena have established a need for resolutions beyond those attainable with SEASAT-A. One method of obtaining higher resolutions would be to fly the instruments aboard airplanes rather than a satellite. The number of aircraft that would be required is estimated along with the rate at which data would be accumulated. Only the East Coast from Maine to Key West is considered. Three different coverage widths are used. The narrowest area is wide enough to cover all bay and estuary regions along the coast; a wider area includes all ocean out to twelve nautical miles from the coast; the maximum size area considered extends out to 200 nautical miles from the coast.

Kuhner, M. B.↗
NASA NTRS1975

The significance of the S-193 Skylab experiment using preliminary data evaluation

The Skylab S-193 radiometer/scatterometer/altimeter experiment is described. The spaceborne microwave system acquires simultaneous radiometric brightness temperature and radar backscatter data over land and ocean. Application of the data analysis to the planning of the GEOS-C and SEASAT-A programs, observation of hurricane Ava, and evaluation of the sensor inflight performance are discussed in terms of using operationally the spaceborne microwave sensors for sensing earth resources phenomena.

Krishen, K.↗