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Some theoretical and experimental results are presented demonstrating the reduction of synthetic aperture radar speckle when a moving diffuser is placed in the processor image plane and is reimaged with a lens whose resolution is not better than the radar resolution. The resolution of the resulting radar image is determined by the resolution of this output lens.
The Poker Flat 49.92-MHz MST radar uses 64 phase-controlled transmitters in individual shelters distributed throughout the antenna array. Phase control is accomplished by sampling the transmitted pulse at the directional coupler of each transmitter and sending the sample pulse back to a phase-control unit. This method requires phase matching 64 long (256 meter) coaxial cables (RG-213) to within several electrical degrees. Tests with a time domain reflectometer showed that attenuation of high frequency components in the long RG-213 cable rounded the leading edge of the reflected pulse so that the cables could only be measured to within 50 cm (about 45 deg at 49.92 MHz). Another measurement technique using a vector voltmeter to compare forward and reflected phase required a directional coupler with unattainable directivity. Several other techniques were also found lacking, primarily because of loss in the long RG-213 cables. At this point it was realized that what was needed was a simple version of the phase-coherent clear-air radar, i.e., a cable radar. The design and operation of this cable are described.
The microwave frequency (MF) partial-reflection radar ran continuously since November 1983, with data being analyzed in real time. The spaced antenna technique was used routinely to produce a climatology of the mean circulation, atmospheric tides, and gravity waves. Since the beginning of 1985, the system was also used as a Doppler radar to measure the spectral widths of the mesospheric echoes. This has enabled the turbulence dissipation rates to be determined. The Stratosphere-Troposphere (ST) radar was operated in the spaced antenna mode to measure winds in November 1984, in conjunction with a cooperative campaign to study the propagation of cold fronts across SE Australia. Observations were also performed to study the structure of the more intense and deeper cold fronts, which occur in late winter.
The synoptic view afforded by orbiting Earth sensors can be extremely valuable for resource evaluation, environmental monitoring and development planning. For many regions of the world, however, cloud cover has prevented the acquisition of remotely sensed data during the most environmentally stressful periods of the year. How synthetic aperture imaging radar can be used to provide valuable data about the condition of the Earth's surface during periods of bad weather is discussed. Examples are given of applications using data from the Shuttle Imaging Radars (SIR) A and B for agricultural land use and crop condition assessment, monsoon flood boundary and flood damage assessment, water resource monitoring and terrain modeling, coastal forest mapping and vegetation penetration, and coastal development monitoring. Recent SIR-B results in Bangladesh are emphasized, radar system basics are reviewed and future SAR systems are discussed.
The synoptic view afforded by orbiting Earth sensors can be extremely valuable for resource evaluation, environmental monitoring and development planning. For many regions of the world, however, cloud cover has prevented the acquisition of remotely sensed data during the most environmentally stressful periods of the year. This paper discusses how synthetic aperture imaging radar can be used to provide valuable data about the condition of the Earth's surface during periods of bad weather. Examples are given of applications using data from the Shuttle Imaging Radars (SIR) A and B for agriculture land use and crop condition assessment, monsoon flood boundary and flood damage assessment, water resource monitoring and terrain modeling, coastal forest mapping and vegetation penetration, and coastal development monitoring. Recent SIR-B results in Bangladesh are emphasized, radar system basics are reviewed and future SAR systems discussed.
Radar echoes from the icy Galilean satellites are unique in character and they may be explained by a phenomenon that was called the radar glory effect. The radar glory backscattering from buried craters was analyzed as a possible model for this effect. These craters have a smaller refractive index below the crater than above. The possibility exists that the rays will be totally internally reflected at the crater walls. The rays which contribute to the backscattering will come from a circular annulus, when viewed before the refraction occurs at the ice-vacuum surface, in a plane orthogonal to the rays reflected from the crater.
The Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) is the most advanced imaging radar system to fly in Earth orbit. Carried in the cargo bay of the Space Shuttle Endeavour in April and October of 1994, SIR-C/X-SAR simultaneously recorded SAR data at three wavelengths (L-, C-, and X-bands; 23.5, 5.8, and 3.1 cm, respectively). The SIR-C/X-SAR Science Team consists of 53 investigator teams from more than a dozen countries. Science investigations were undertaken in the fields of ecology, hydrology, ecology, and oceanography. This report contains 44 investigator team reports and several additional reports from coinvestigators and other researchers.
We have assembled all currently processed radar data from 1989 to 1998 into crude images covering the Kuiper (H6) region on Mercury. The data used were taken to support the ephemeris improvement and gravitational physics programs; however, the resolution is good enough in some cases to make north/south ambiguous images that show some features that can be identified with the Mariner 10 features. Topography profiles along the apparent equator are also available; some of these profiles show ridges and rills as well as crater depths and diameters. The combination of the optical imaging and the radar imaging can be helpful in understanding similar features in radar images of the optically unimaged hemisphere.
High-resolution radar images of Moreno Glaciar, Argentina, acquired by the Shuttle Imaging Radar C (SIR-C) on October 9 and 10 1994, at 24-cm wavelength (L-band), are utilized to map the glacier velocity both interferometrically and using a novel feature tracking technique.
This paper examines the relationship between the phase measured by a radar polarimeter and a radar interferometer.
Radar scatter from rough surfaces with application to lunar radar backscatter
Radar reflectivity correlations with lunar surface structure in Mare Imbrium, using delay-Doppler radar maps
Numerical analysis of radar echo pulse response to compute expected return pulse amplitude and shape for planetary radar altimeters
The capabilities are analyzed of a real aperture, forward-looking imaging radar for use as an independent landing monitor, which will provide the pilot with an independent means of assessing the progress of an automatic landing during Category 3 operations. The analysis shows that adequate ground resolution and signal-to-noise ratio can be obtained to image a runway with grassy surroundings using a radar operating at 35 GHz in good weather and in most fog but that performance is severely degraded in moderate to heavy rain and wet snow. Weather effects on a 10 GHz imager are not serious, with the possible exception of very heavy rain, but the azimuthal resolution at 10 GHz is inadequate with antennas up to 2 m long.
The Jicamarca radar (Long. 76.52W, Lat. 11.56S), located at 20 km from Lima at approximately 500 meters over sea level, is surrounded by mountains which provide a good shield from man-made interference. The radio horizon goes from a few hundred meters, across the dry valley where it is located, to 15 km, along the valley in the direction of the continental divide. This limits the clutter to 15 km, except for one high peak at 21 km. It is the most equatorial of all existing MST radars. Its proximity to the Andes, makes its location unique for the study of lee waves and orographic-induced turbulence. Vertical as well as horizontal projections of MST velocities are obtained by simultaneously pointing with different sections of the antenna into three or four different directions. The transmitters, receivers, and systems for data acquisition, processing, and control are included.
As a first step in interchange of data from the Urbana mesosphere-stratosphere-troposphere (MST) radar, a sample tape has been prepared in 9-track 1600-bpi IBM format. It includes all Urbana data for April 1978 (the first month of operation of the radar). The 300-ft tape contains 260 h of typical mesospheric power and line-of-sight velocity data.
The 'OCTOPOD' radar extends the concept of differential reflectivity (ZDR) to multiple polarization planes, so that ZDR measurements can be made in any pair of orthogonal linear polarizations. This allows the mean canting angle of oblate raindrops or ice particles to be determined. Attention is given to the radar hardware employed, the rotating feed system that generates the multiple polarization planes, and the computer controlled data acquisition system which extracts both reflectivity and ZDR data.
A one-dimensional model for simulating azimuthal SAR imaging of the ocean surface is developed which can admit both the 'distributed surface' and 'velocity bunching' approaches. Computer simulations demonstrate that the time-dependent modulation patterns due to the radar cross section variation and the velocity bunching effects provide optimum focusing around half the phase velocity of the long wave. The results indicate that in the Tower Ocean Wave and Radar Dependence experiment, SAR imaging at L band is approximately linear.