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At least 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Four channel simultaneous X-L band imaging SAR radar

Design considerations, construction, and testing of a four-channel microwave radar imaging system are described. Various components of the system are described in some detail including the receiver, transmitter, recorders, and the general timing circuitry. Results from flight tests of the system are described. The system is unique in that images from four microwave channels are provided and the data is obtained simultaneously. Energy is radiated at both 3 cm and 25 cm wavelengths; the four receiving channels are 3 cm, like and crossed polarization and 25 cm, like and crossed polarization.

Rawson, R.↗
NASA NTRS1976

Interpretation key for SAR /L-band/ imagery of sea ice

An interpretation key, similar to those previously developed for use with aerial photography and other remotely sensed data, was developed for L-band (25 cm) radar imagery collected over the Arctic Ocean. Data from April, August, and October were considered. The procedure for developing a valid interpretation key for operation use involves substituting time for space. Open water situations (polynyas, leads, flaws), examples of unconsolidated ice (frazil, slush, brash), thin ice (nilas), and annual ice (first year, multi-year ice) situations are examined. It is suggested that the interpretation key will enhance the use of side looking airborne radar data in the qualitative photo interpretation mode.

Bryan, M. L.↗
NASA NTRS1977

A solution to the problem of SAR range curvature

When synthetic aperture radar systems are pushed to attain finer resolution at larger ranges than was previously the case for remote sensing purposes, the geometric signal aberration known as range curvature arises. Known techniques for correcting range curvature are exact at only one selected range, thus forcing neighboring ranges to use the same correction as an approximation. A solution to the problem is proposed that is exact at all ranges, thus simplifying and improving the image processing for such systems.

Raney, R. K.↗
NASA NTRS1978

Low loss, flexible, lightweight corporate RF feed system for SAR antenna application

Mechanical and electrical efficiency constraints imposed by the SEASAT-A synthetic aperture radar antenna posed difficult design problems. After consideration of available standard cable and waveguide systems, it was determined that an optimum design could be obtained from a suspended substrate RF feed system. Size and mechanical flexibility constraints forced the design of a flexible, suspended substrate section capable of 180-degree flexure. Original design goal for insertion loss over power division was 1 db; measured results indicated 0.6 db maximum across the band. Multipactor testing of system components indicated system breakdown capability in excess of 4 kW compared to a specification input maximum of 1500 W.

Schiavone, F.↗
NASA NTRS1978

Electronic SAR processors for space missions

An experimental laboratory processor is being developed as a testbed for design of on-board processors for future space missions. The configuration of the experimental processor is described and technical factors pertaining to the design are discussed.

Wu, C.↗
NASA NTRS1978

Applications and limitations of very large-scale integration in SAR azimuth processing

The major limitation of a convolution processor designed with CCD memory chips is the inability to operate in real time except for slow aircraft speeds or coarse resolutions. Two methods of summing the products were evaluated with respect to speed, power, and space requirements. A convolution processor was designed, and the number of chips as well as the power and volume requirements were determined using 4, 6, and 8 bit data words. The processor is flexible because range samples may be traded for additional azimuth samples by altering the control signals. The processor is also modular, and additional range or azimuth may be processed by adding more cards.

Kuhler, D. G.↗
NASA NTRS1977

Computer processing of SAR L-band imagery

The described work in the areas of hydrology and polar ice defines possible uses of automatic picture processing of uncalibrated radar images. The data used in the study were collected with the aid of an L-band synthetic aperture radar mounted in the NASA CV-990 aircraft. The radar was operated at approximately 30,000 feet altitude. One study area used was located in the Beaufort Sea and contained sea ice. The other study area contained lakes on the Alaskan North Slope. The reported investigations demonstrate that certain types of features can be efficiently studied by using simple automatic picture processing techniques applied to uncalibrated radar data.

Bryan, M. L.↗
NASA NTRS1978

Electronic SAR processors for space missions

This paper reports some interim results relating to an on-going effort to develop an electronic processor for real-time processing of synthetic aperture radar data. An experimental laboratory processor is being developed as a testbed for design of onboard processors for future space missions. This paper describes the configuration of the experimental processor and discusses technical factors pertaining to the design.

Wu, C.↗
NASA NTRS1980

Concerning the feasibility of a real time SAR digital processor for VOIR low resolution imaging modes

The feasibility of real time digital processing of synthetic aperture radar data for Venus orbiting imaging radar low resolution modes was investigated. First, it is shown that range migration is not a problem for these modes. Then, under the assumption of no range migration, fast Fourier transform implementations for accomplishing both range and azimuth correlation in real time are shown to be feasible with current technology.

Truong, T. K.↗
NASA NTRS1980

Feasibility and cost study on VOIR SAR data transfer via a bent pipe link

An INTELSAT/DOMSAT double hop bent pipe link for the Venus orbiting imaging radar synthetic aperture radar imaging data transfer from deep space stations 43 and 63 to the Jet Propulsion Laboratory was investigated. The cost for the bent pipe transfer was estimated and compared to that for the planned tape record/airfreight-the-tape transfer method.

Park, Y. H.↗
NASA NTRS1980

The Seasat SAR Wind and Ocean Wave Monitoring Capabilities: A case study for pass 1339m

A well organized low energy 11 sec. swell system off the East Coast of the U.S. was detected with the Seasat Synthetic Aperture Radar and successfully tracked from deep water, across the continental shelf, and into shallow water. In addition, a less organized 7 sec. system was tentatively identified in the imagery. Both systems were independently confirmed with simultaneous wave spectral measurements from a research pier, aircraft laser profilometer data, and Fleet Numerical Spectral Ocean Wave Models.

Beal, R. C.↗
NASA NTRS1983

Spaceborne SAR and sea ice

A number of remote sensing systems deployed in satellites to view the Earth which are successful in gathering data on the behavior of the world's snow and ice covers are described. Considering sea ice which covers over 10% of the world ocean, systems that have proven capable to collect useful data include those operating in the visible, near-infrared, infrared, and microwave frequency ranges. The microwave systems have the essential advantage in observing the ice under all weather and lighting conditions. Without this capability data are lost during the long polar night and during times of storm passage, periods when ice activity can be intense. The margins of the ice pack, a region of particular interest, is shrouded in cloud between 80 and 90% of the time.

Weeks, W. F.↗
NASA NTRS1983

Sea Height Information from Complex SAR Data

Synthetic aperture radar data was used to construct an estimation algorithm for development of information on long waves. The evolution of chaotic dynamic systems was also explored.

Harger, R. O.↗
NASA NTRS1984

SAR maritime missions

The U.S. Coast Guard missions (search and rescue, enforcement of laws and treaties, marine environmental patrol, and light utility transport) are discussed.

Young, D. A.↗
NASA NTRS1984

Quantitative use of multiincidence-angle SAR for geologic mapping

It is proposed that techniques be developed and used for quantitative interpretation of shuttle imaging radar-B (SIR-B) data for lithologic identification and mapping. The use of backscatter versus incidence angle signatures derived from SIR-B images is to be investigated. The use of SIR-B with other sensors for geologic mapping is also to be considered. Anticipated results are discussed in terms of geologic mapping.

Farr, T. G.↗