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Topic: Synthetic aperture radar

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	Synthetic aperture radar - Wikipedia, the free encyclopedia
		Synthetic aperture radar (SAR) is a form of radar in which sophisticated post-processing of radar data is used to produce a very narrow effective beam.
		Synthetic aperture radar was first used by NASA on JPL's Seasat oceanographic satellite in 1978 (this mission also carried an altimeter and a scatterometer); it was later developed more extensively on the Spaceborne Imaging Radar (SIR) missions on the space shuttle in 1981, 1984 and 1994.
		The Cassini mission to Saturn is currently using SAR to map the surface of the planet's major moon Titan, whose surface is partially hidden from direct optical inspection by atmospheric haze.
	en.wikipedia.org /wiki/Synthetic_aperture_radar (2267 words)

	What is Synthetic Aperture Radar? -- Sandia National Laboratories
		Synthetic aperture radar complements photographic and other optical imaging capabilities because of the minimum constraints on time-of-day and atmospheric conditions and because of the unique responses of terrain and cultural targets to radar frequencies.
		Synthetic aperture radar technology has provided terrain structural information to geologists for mineral exploration, oil spill boundaries on water to environmentalists, sea state and ice hazard maps to navigators, and reconnaissance and targeting information to military operations.
		Range measurement and resolution are achieved in synthetic aperture radar in the same manner as most other radars: Range is determined by precisely measuring the time from transmission of a pulse to receiving the echo from a target and, in the simplest SAR, range resolution is determined by the transmitted pulse width, i.e.
	www.sandia.gov /radar/whatis.html (798 words)

	What is imaging radar ?/jpl
		Thisbackscatter returns to the radar as a weaker radar echo and is received by the antenna in a specific polarization (horizontal or vertical, not necessarily the same as the transmitted pulse).
		As the radar moves, a pulse is transmitted at each position; the return echoes pass through the receiver and are recorded in an 'echo store.' Because the radar is moving relative to the ground, the returned echoes are Doppler-shifted (negatively as the radar approaches a target; positively as it moves away).
		The trick in SAR processing is to correctly match the variation in Doppler frequency for each point in the image: this requires very precise knowledge of the relative motion between the platform and the imaged objects (which is the cause of the Doppler variation in the first place).
	southport.jpl.nasa.gov /desc/imagingradarv3.html (1912 words)

	Inverse synthetic aperture radar - Wikipedia, the free encyclopedia
		This operation is equivalent to the generation of a large synthetic aperture phased array antenna formed by the coherent summation of the receiver outputs for varying target / antenna geometries.
		This occurs when the synthetic aperture to the target range is less than required by the 2D2/lambda limit where D is the required lateral extent of the target.
		At this point the synthetic aperture is within the target nearfield region and requires focusing.
	en.wikipedia.org /wiki/Inverse_synthetic_aperture_radar (1206 words)

	Synthetic Aperture Radar
		Writing the radar equation for an area target is based on the assumption that the observed area may be considered as a collection of many point scatterers, where no individual target dominates the scattered signal.
		The imaging zone of a remote-sensing radar typically consists of a horizontally thin swath extending from the side of the platform and orthogonal to the direction of motion of the platform.
		This conflict is usually avoided with the use of a Synthetic Aperture Radar (SAR), which removes the dependence of the azimuth resolution on the incidence angle.
	www.csr.utexas.edu /projects/rs/whatissar/rar.html (1453 words)

	4.3 Synthetic Aperture Radar (Site not responding. Last check: 2007-11-07)
		Synthetic aperture processing is a complicated data processing of received signals and phases from moving targets with a small antenna, the effect of which is to should be theoretically convert to the effect of a large antenna, that is a synthetic aperture length, as shown as Figure 4.3.1.
		The synthetic aperture length is the beam width by range which a real aperture radar of the same length, can project in the azimuth direction.
		Therefore the satellite with SAR is required to be high, because the correction for synthetic aperture processing due to instability at lower altitudes is very difficult.
	www.profc.udec.cl /~gabriel/tutoriales/rsnote/cp4/cp4-3.htm (308 words)

	Mid-Atlantic RESAC Wetland Mapping with Synthetic Aperture Radar
		Radar sensors also have the potential to penetrate vegetative canopies to detect the character of the ground layer, soil moisture, and flooding beneath the canopy (Kasischke and Bourgeau-Chavez, 1997; Kasischke et al., 1997a; Kasischke et al., 1997b).
		Radar not only has potential to detect different types of wetlands; it can also be used to study the condition and function of these valuable areas.
		Radar data holds potential for the mapping of wetlands but this potential has not been fully explored and the techniques needed too do so are not as well developed as those of optical data.
	www.geog.umd.edu /resac/wetlands-sar.htm (1585 words)

	Synthetic Aperture Radar (SAR)
		Synthetic aperture radar (SAR) is basically a method of ground mapping that uses computer processing to make radar work better.
		SAR uses antennas positioned on moving bodies, such as satellites, and then mathematically combines the separate signals transmitted as the antenna moves, simulating or mimicking the transmission of radar from a source with a larger “aperture,” or a larger opening.
		The motion of the satellite, combined with the wide beam of the radar, covers a swath along the ground, allowing a large area to be searched quickly--typically 256 square kilometers.
	www.centennialofflight.gov /essay/Dictionary/SAR/DI175.htm (186 words)

	Synthetic-Aperture Radar (Site not responding. Last check: 2007-11-07)
		Synthetic-aperture radars (SARs) synthesize a large aperture by coherently integrating the returned signal pulse-to-pulse as the radar moves.
		The formation of synthetic apertures and associated processing is most easily understood from the standpoint of Doppler processing.
		Consider a fixed radar pointing at a target on a rotating turntable, where both the radar and the target lie on the same plane.
	www.aero.org /publications/crosslink/summer2004/04_sidebar1.html (474 words)

	Theory of Synthetic Aperture Radar
		This spread is due to interference of the waves emitted from and received by the dipoles of the antenna, which causes the angular spread to decrease as the aperture length increases (a longer antenna produces a tighter beam, much as a longer barrel of a gun produces less dispersion).
		The situation for a SAR is very much different, however, in that ground objects will be placed into locations on the image line as a function of their distance from the antenna--not as a function of their distance from each other on the ground.
		For the perfect specular reflector, radar returns (backscatter) exist only near vertical incidence (due to a 90º depression angle or the slope of the surface) and the reflected energy is localized to a small angular region around the angle of reflection.
	www.geo.unizh.ch /~fpaul/sar_theory.html (4631 words)

	Inverse Synthetic Aperture Imaging Radar
		The radar can be treated as an interferometer with the mixer forming an output related return signal at the mixer output can be derived as a function of, the phase difference between the signal and LO mixer inputs.
		This occurs when the synthetic aperture to the target range is less than required by the 2D2/lambda limit where D id the required lateral extent of the target.
		A technique for transforming radar data acquired at a given location in space to another location in space (i.e., the form the near-field to the far field) is to form a fully focused ISAR image of the target region and then use that image as a target model.
	www.nearfield.com /amta/amta85ds.htm (3732 words)

	Remote Sensing with Radar: Seeing Earth in a New Way
		To accomplish all this, SAR transmits pulses of microwave energy toward Earth and measures the strength and time delay of the energy that is scattered back to the antenna.
		SAR was originally developed in the 1950s as a technique for improving the resolution for military reconnaissance radars, but is now widely used in many countries for civilian applications.
		SAR data are also being used by geologists in studies of past climates and volcanic and earthquake hazards.
	www.agu.org /sci_soc/evans.html (1614 words)

	SYNTHETIC APERTURE RADAR (Site not responding. Last check: 2007-11-07)
		Synthetic aperture radar (SAR) is a system that moves a radar antenna having a small aperture while taking multiple radar measurements of the same scene.
		The amount of detail available using this technique is equivalent to the detail that would be obtained using a radar with a much larger aperture, thus it is called a synthetic aperture.
		The primary ECEn 461 project for this semester is to design and construct several of the major passive components of a microstrip SAR system, including a Wilkinson divider, a branch line coupler, and a microstrip filter.
	class.et.byu.edu /ee460/SAR1lab.htm (423 words)

	Cassini-Huygens: Spacecraft-Instruments-Cassini Radio Detection and Ranging Instrument (Radar)
		Another great feature of radar is that it can pierce through an atmosphere, even one as thick and murky as the one engulfing Titan.
		By bouncing radio signals off Titan's surface and timing their return, the RADAR is producing maps of Titan's surface and measuring the height of surface objects such as mountains and canyons.
		Radar (an acronym that stands for "radio detection and ranging") can operate in three ways: imaging, altimetry and radiometry.
	saturn.jpl.nasa.gov /spacecraft/instruments-cassini-radar.cfm (409 words)

	Synthetic Aperture Radar (Site not responding. Last check: 2007-11-07)
		The payoff is a greatly reduced cost of SAR satellites because of the substantially lower weight.
		Because a stretched membrane SAR can be physically large, as it orbits it can obtain high resolution images of Earth targets even for large electromagnetic wavelengths.
		Radar images can be obtained through all kinds of weather, and ground foliage can be penetrated.
	lgarde.com /programs/sar.html (176 words)

	Synthetic Aperture Radar (SAR)
		In fact, the SAR is generally able to transmit several hundred pulses while a spacecraft passes over a particular object.
		The synthetic aperture in this case, therefore, is the distance traveled by the spacecraft while the radar antenna collected information about the object.
		The ERS-1 satellite's SAR sends out around 1700 pulses a second, collects about a thousand backscattered responses from any single object while passing overhead, and the resulting processed image has a resolution near 30 meters.
	geology.isu.edu /~chadjohn/class_9_files/slide0048.htm (204 words)

	Satellite Geodesy, IGPP, SIO, UCSD \| Synthetic Aperture Radar Interferometry
		CRUSTAL STRAIN AND TOPOGRAPHY FROM SYNTHETIC APERTURE RADAR INTERFEROMETRY
		Evidence for on-going inflation of the Socorro magma body, New Mexico, from Interferometric Synthetic Aperture Radar imaging, Geophys.
		Synthetic Aperture Radar data are from the European Space Agency Satellite ERS-2 satellite.
	topex.ucsd.edu /SAR (268 words)

	Remote Sensing of the Environment : Synthetic Aperture Radar
		From Equation 2.18, the angular horizontal beam width of a real-aperture radar is[1]
		is the horizontal beam width of the synthetic aperture, and is half that of a real aperture [Ulaby, Moore, and Fung 1986b].
		However, most SAR data are not processed at the minimum possible resolution because of the need to average the returns over several neighboring resolution cells, (i.e.
	www.csr.utexas.edu /rs/sensors/whatissar/sar.html (361 words)

	Synthetic Aperture Radar
		Synthetic Aperture Radar (SAR) is an active remote sensing technology which uses microwave electromagnetic energy to form complex images of terrain reflectivity.
		Because SAR is largely unaffected by the presence of dense cloud cover, it delivers flexibility over weather constraints, and introduces the possibility of nighttime operations.
		The image was generated by engineers at NGS from raw phase history data acquired aboard the Environmental Research Institute of Michigan (ERIM) DCS aircraft, and using image formation code written at Sandia National Labs (SNL).
	www.ngs.noaa.gov /RESEARCH/RSD/main/sar/sar.shtml (340 words)

	Technology - Synthetic Aperture Radar (SAR)
		Classificatiuon of multi-temporal SAR images and INSAR coherence images using adaptive neighborthood model and simulated annealing approach
		Polarimetric radar data analysis of key landcover features in the coastal panay area: a preparatory tool for polarimetric sar image classification
		SAR interferometry technology and applications - an verview in the contest of Indian insar group activities
	www.gisdevelopment.net /technology/sar (388 words)

	Synthetic aperture radar interferometry
		Synthetic aperture radar (SAR) is a coherent active microwave imaging method.
		In remote sensing it is used for mapping the scattering properties of the Earth's surface in the respective wavelength domain.
		Interferometric SAR (InSAR) exploits the phase differences of at least two complex-valued SAR images acquired from different orbit positions and/or at different times.
	stacks.iop.org /0266-5611/14/R1 (365 words)

	Interferometric Synthetic Aperture Radar - Elevation (IFSARE)
		The Interferometric Synthetic Aperture Radar - Elevation (IFSARE) was developed by Environmental Research Institute of Michigan (ERIM), Ann Arbor, Mich., under a Defense Advanced Research Projects Agency (DARPA) project.
		A by-product of the DTEM generation is high-quality Synthetic Aperture Radar (SAR) imagery with an image resolution of approximately 3 meters.
		The agreement allows Intermap to commercialize an important military radar technology (interferometric synthetic aperture radar), while maintaining the Department of Defense's low-cost access to the system's capability to produce accurate, detailed maps and digital terrain elevation models.
	www.fas.org /irp/program/collect/ifsare.htm (865 words)

	EOS Volcanology Acronyms List
		An advanced synthetic aperture radar has been selected as the payload for the Envisat-1 payload, which has a planned launch in 2000.
		The radar has a fixed incidence angle (35 degrees) which was selected for land studies, specifically geology and mineral exploration.
		A radar instrument flown with SIR-C on the Space Shuttle STS-59 in April, 1994, and on STS-68 in September-October, 1994.
	eos.higp.hawaii.edu /acronyms.html (2789 words)

	NOVA \| Spies That Fly \| Imaging With Radar \| PBS
		With its ability to "see" in complete darkness and through rain and clouds in the sky and snow and foliage on the ground, SAR (pronounced "sar" rather than "S-A-R") is becoming a regular component of unmanned aerial vehicles, or UAVs.
		Other useful applications for SAR include mapping planets (such as the perpetually cloud-covered Venus), mapping terrain here on Earth, and even looking for signs of earthquakes.
		For some, what's most fascinating about SAR is not what it can "image" or even that it can produce remarkably high-quality pictures, but that an image can be created at all using radar waves and a moving antenna.
	www.pbs.org /wgbh/nova/spiesfly/radar.html (195 words)

	ATI's Advanced Synthetic Aperture Radar course
		This course is designed for those who have already taken a basic synthetic aperture radar (SAR) class and/or have working experience with SAR systems design and applications technologies.
		Huxtable specializes in integrated performance evaluations of SAR and processor system combinations, including SAR design simplifications made possible by state-of-the-art data processing systems.
		SAR activities in DoD, NASA and commercial applications.
	www.aticourses.com /advanced_synthetic_aperture_radar.htm (368 words)

	Advanced Synthetic Aperture Radar System [ASARS-2] (Site not responding. Last check: 2007-11-07)
		The Advanced Synthetic Aperture Radar System [ASARS-2] is a multimode real-time, high-resolution reconnaissance system carried on the U-2 with all-weather, day-night, long-range mapping capabilities.
		The radar is capable of producing extremely high resolution images from long stand-off ranges and provides the highest resolution radar ground maps available today.
		However, a preferred option is to reallocate a portion of the AIP and other sensor funds to create a power distribution architecture to serve all planned and future sensor power requirements.
	www.fas.org /irp/program/collect/asars-2.htm (256 words)

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