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NASA NTRS1983

L band SAR ocean wave observations during Marsen

The five-sided flight pattern made it possible to view the same ocean surface patch from five different directions. The results obtained from analyzing radar and in situ measurements indicate that the focus dependence for optimum imaging is that for a surface moving with a speed that is approximately equal to the wave phase velocity. The finding also suggest that azimuthally traveling waves can be visible as range traveling waves when the necessary focus adjustments are made in the SAR processor and that the visibility of azimuthally travelling waves does not improve with decreasing integration time. What is more, the spectra and images of azimuthally traveling waves do not show observable distortions compared with those for range traveling waves.

Jain, A.↗

NASA NTRS1985

SAR imaging of waves in water and ice - Evidence for velocity bunching

Synthetic aperture radar (SAR) images collected over the Arctic marginal ice zone show gravity wave patterns in both the open water and the ice. Diffuse wave patterns are visible in the water at near range (small incidence angles), while most distinct wave patterns are visible in the ice across the entire swath. The wave patterns in the ice appear as bright lines rather than sinusoidal intensity variations. Additionally, the images show a periodic displacement of the ice/water boundary, apparently due to Doppler shift effects associated with the gravity wave orbital motions. These observations are interpreted as evidence for the velocity bunching effect and also illustrate the effects of random scatterer motions in the open water.

Lyzenga, D. R.↗

NASA NTRS1985

On the use of L-band multipolarization airborne SAR for surveys of crops, vineyards, and orchards in a California irrigated agricultural region

The airborne L-band synthetic aperture radar (SAR) collected multipolarization calibrated image data over an irrigated agricultural test site near Fresno, CA, on March 6, 1984. The conclusions of the study are as follows: (1) the effects of incidence angle on the measured backscattering coefficients could be removed by using a correction factor equal to the secant of the angle raised to the 1.4 power, (2) for this scene and time of year, the various polarization channels were highly correlated such that the use of more than one polarization added little to the ability of the radar to discriminate vegetation type or condition; the exception was barley which separated from vineyards only when a combination of like and cross polarization data were used (polarization was very useful for corn identification in fall crops), (3) an excellent separation between herbaceous vegetation (alfalfa, barley, and oats) or bare fields and trees in orchards existed in brightness was well correlated to alfalfa height or biomass, especially for the HH polarization combination, (5) vineyards exhibited a narrow range of brightnesses with no systematic effects of type or number of stakes nor of number of wires in the trellises nor of the size of the vines, (6) within the orchard classes, areal biomass characterized by basal area differences caused radar image brightness differences for small to medium trees but not for medium to large trees.

Paris, J. F.↗

NASA NTRS1984

Programmable Real-Time Acousto-Optic/CCD SAR processor

The theory of operation of the Real-Time Acousto-Optic SAR Processor is reviewed and recent experimental results are presented. The results include a demonstration of the real-time imaging capability of the processor with simulated radar signals. An advanced version of this processor is then described in which a programmable reference function is entered via a second acousto-optic device to eliminate the need for a 2-D SLM. In this implementation the reference function is updated by electronic means to give the processor the flexibility to adapt rapidly to changes in the parameters of the radar/target geometry.

Haney, M.↗

NASA NTRS1985

Spaceborne SAR antenna technology and the Shuttle Imaging Radar-B (SIR-B) antenna development

Shuttleborne SAR systems have been developed jointly by NASA and JPL for remote sensing research. NASA initially entered the field of spaceborne imaging in June 1978 with the launch of Seasat. In November 1981 the Space Agency launched the Shuttle Imaging Radar-A (SIR-A) and SIR-B was lifted into orbit in October 1984. One of the key technical developments in this program is the microstrip planar antenna used to synthesize a large array for high ground resolution. This paper discusses the technology development of these spaceborne antennas with emphasis on the Shuttle Imaging Radar-B (SIR-B) system.

Schaeper, H. R. A.↗

NASA NTRS1985

Multipolarization SAR data for surface feature delineation

This paper presents the techniques and the utility of multipolarization Synthetic Aperture Radar (SAR) data for surface feature delineation. Three channels of ratioed data (VV/HH, VH/HH, and VH/VV) are generated from the HH, VV, and VH polarization data (V = vertical, H = horizontal). The technique assumes redundancy of the VH and HV polarization and only VH polarization is used. The ratioed data are linearly stretched to yield a digital number within a range of 0 to 255. Based on the separability measure for two-class delineation, it was found that (1) the ratioed data resulted in a better delineation of surface features with high like (HH or VV) polarization digital number, and (2) the use of ratioed data provided further information not available from the original three-polarization data. The results suggest an advantage in using the ratioed data and the original three-polarization data for surface feature delineation.

Wu, S. T.↗

NASA NTRS1985

Simulations of SAR wave spectra using high spectral resolution estimates from the SCR and ROWS instruments

A numerical model for predicting the synthetic aperture radar (SAR) image of a moving ocean surface is described, and results are presented for two SIR-B data sets collected off the coast of Chile. Wave height spectra measured by the NASA radar ocean wave spectrometer (ROWS) and surface contour radar (SCR) were used as inputs to this model, and results are compared with actual SIR-B image spectra from orbits 91 and 106.

Lyzenga, D.↗

NASA NTRS1986

An alternative multi-mode SAR for RADARSAT

The RADARSAT project was asked by the Canadian government in the spring of 1986 to design for reduced costs and increased radar performance as compared to the well-known baseline design. Both the Project Office and Canadian industry (lead by SPAR Aerospace of Montreal) have undertaken to meet this request, with a proposal to cabinet to be submitted in the fall of 1986. One alternative SAR concept is outlined which is under consideration for a revised RADARSAT configuration. The radar system described uses two frequencies (C&L band) over four possible modes: near range swath; far range swath; wide swath; and high resolution. Good sensitivity, resolution, and coverage are obtained with modest power and data rates. The antenna systems are relatively simple. Indeed, no break-through technological developments are needed. The design allows several mode combinations for simultaneous data collection or performance enhancement. The principal parameters are described. A nominal mean altitude of 700 km is assumed.

Raney, R. K.↗

NASA NTRS1986

Solutions to bi-Maxwellian transport equations for SAR-arc conditions

The first subsonic solutions of the bi-Maxwellian-based 16-moment set of transport equations for stable auroral red (SAR) arc conditions are presented. These are compared with the solutions obtained from the Maxwellian-based 13-moment transport equations for the same boundary conditions. Close agreement between the 16-moment and 13-moment solutions was obtained for the drift velocity, total electron temperature, total proton heat flow, and total electron heat flow profiles. On the other hand, significant discrepancies were found. Thus, the 16-moment density profile falls off more rapidly with increasing altitude than that computed with the 13-moment equations; the total proton temperature is less in the 16-moment case than in the 13-moment case by several thousand degrees at most altitudes; and differences exist in the ratios of the proton and electron temperature anisotropies with the altitude. A simplified set of transport equations was obtained by dropping terms which remain relatively small at all altitudes.

Demars, H. G.↗

NASA NTRS1987

A post-processing system for automated rectification and registration of spaceborne SAR imagery

An automated post-processing system has been developed that interfaces with the raw image output of the operational digital SAR correlator. This system is designed for optimal efficiency by using advanced signal processing hardware and an algorithm that requires no operator interaction, such as the determination of ground control points. The standard output is a geocoded image product (i.e. resampled to a specified map projection). The system is capable of producing multiframe mosaics for large-scale mapping by combining images in both the along-track direction and adjacent cross-track swaths from ascending and descending passes over the same target area. The output products have absolute location uncertainty of less than 50 m and relative distortion (scale factor and skew) of less than 0.1 per cent relative to local variations from the assumed geoid.

Curlander, John C.↗

NASA NTRS1987

Synergism requirements and concepts for SAR and HIRIS on EOS

A study is conducted to ascertain the synergistic advantages obtainable by combining, in the EOS orbital instrument platform, instruments for the optical and microwave measurements of biophysical properties important in ecosystem modeling. Attention is given to the comparative coverages of the SAR, HIRIS, TIMS and MODIS instruments that will be carried by the platform, and to the ongoing development of joint inversion algorithms for the modeling of the ecosystems-related data thus obtained. A three-dimensional characterization of the physical attributes of the vegetation canopy and its background surface will be attempted.

Cimino, J. B.↗

NASA NTRS1987

SAR (Synthetic Aperture Radar). Earth observing system. Volume 2F: Instrument panel report

The scientific and engineering requirements for the Earth Observing System (EOS) imaging radar are provided. The radar is based on Shuttle Imaging Radar-C (SIR-C), and would include three frequencies: 1.25 GHz, 5.3 GHz, and 9.6 GHz; selectable polarizations for both transmit and receive channels; and selectable incidence angles from 15 to 55 deg. There would be three main viewing modes: a local high-resolution mode with typically 25 m resolution and 50 km swath width; a regional mapping mode with 100 m resolution and up to 200 km swath width; and a global mapping mode with typically 500 m resolution and up to 700 km swath width. The last mode allows global coverage in three days. The EOS SAR will be the first orbital imaging radar to provide multifrequency, multipolarization, multiple incidence angle observations of the entire Earth. Combined with Canadian and Japanese satellites, continuous radar observation capability will be possible. Major applications in the areas of glaciology, hydrology, vegetation science, oceanography, geology, and data and information systems are described.

Source record↗

NASA NTRS1987

Quantitative use of satellite SAR imagery of sea ice

An automatic technique to obtain ice motion based on maximizing cross-correlation and employing a strategy of nested calculations has been developed and used to obtain displacements of more than 2000 tie-points on a 2 km mesh grid. The mean displacement error is 250 m and is as low as manual data error of 150 m on rigid pieces. The method allows tie-points to be found on a regular grid in a fully automatic fashion. Full resolution data are not needed to maximize the accuracy of displacement measurements, a result which is significant for SAR images, with their large amounts of data.

Fily, M.↗

NASA NTRS1988

The effects of undersampling on multipolarization SAR images

The scattering matrix and Stokes matrix formats for multipolarization synthetic aperture radar (SAR) images are introduced. The effects of converting to the Stokes matrix format, without first doubling the sampling rate to allow for the conversion from a complex to an intensity format is quantified and discussed. It is shown that for most applications the Stokes matrix format is acceptable, since errors introduced by undersampling tend to average out when large numbers of pixels are averaged. For those applications requiring analysis of single image pixels, the scattering matrix format is recommended.

Freeman, A.↗

NASA NTRS1990

Computer Assembles Mosaics Of Satellite-SAR Imagery

Digital image-processing system assembles maplike mosaic images of large areas of Earth from overlapping images of smaller areas generated by spaceborne synthetic-aperture radar (SAR). Automatically registers and blends smaller images with each other. Eliminates need for time-consuming, tedious manual processing. Modifiable to accept images from spaceborne optical sensors.

Kwok, R.↗

NASA NTRS1990

Making Mosaics Of SAR Imagery

Spaceborne synthetic-aperture-radar (SAR) images useful for mapping of planets and investigations in Earth sciences. Produces multiframe mosaic by combining images along ground track, in adjacent cross-track swaths, or in ascending and descending passes. Images registered with geocoded maps such as ones produced by MAPJTC (NPO-17718), required as input. Minimal intervention by operator required. MOSK implemented on DEC VAX 11/785 computer running VMS 4.5. Most subroutines in FORTRAN, but three in MAXL and one in APAL.

Curlander, John C.↗

NASA NTRS1990

Making Topographical Maps From SAR and Flood-Gauge Data

Collection of computer programs processes image data obtained by synthetic-aperture radar (SAR) along with measurements of water levels taken at selected points on ground to generate three-dimensional maps of surveyed terrain. Information in maps presented in variety of useful ways suited to study of such phenomena as flooding, damage caused by floods, flow of nutrients from forests to river and marine ecosystems, and effects of subsidence of ground or of rising sea levels.

Imhoff, Marc Lee↗

NASA NTRS1989

Alaska SAR Facility Mission planning software - An interactive mission planning system

The Alaska Synthetic Aperture Radar (SAR) Facility Mission Planning Subsystem is an interactive mission planning software system on the VAXStation 2000. This system has the capability to generate satellite ephemerides and mission parameters related to synthetic aperture radar missions. The mission data can be viewed as overlays on the world map in various projections and zooms. The system also provides schedule planning capabilities, using the INGRES DBMS to keep track of the various plans and schedules generated by the mission planner.

Lo, Martin W.↗