Synthetic-aperture radar

synthetic aperture radarSARsynthetic apertureSynthetic Aperture Radar (SAR)radar mappingAdvanced Synthetic Aperture Radar Systemantenna aperture synthesisAperture synthesisdoppler beam-sharpeningDoppler-Beam Sharpening
Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes.wikipedia
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3D reconstruction

3D imagingreconstruction3-D virtual reconstruction
Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes.
Digital elevation models can be reconstructed using methods such as airborne laser altimetry or synthetic aperture radar.

Inverse synthetic-aperture radar

inverse synthetic aperture radarinverse SARISAR
SAR can also be implemented as inverse SAR by observing a moving target over a substantial time with a stationary antenna.
It is analogous to conventional SAR, except that ISAR technology utilizes the movement of the target rather than the emitter to create the synthetic aperture.

Side looking airborne radar

side-looking airborne radarside-looking radarSLAR
SAR is typically mounted on a moving platform, such as an aircraft or spacecraft, and has its origins in an advanced form of side looking airborne radar (SLAR).
SLAR can be fitted with a standard antenna (real aperture radar) or an antenna using synthetic aperture.

Interferometric synthetic-aperture radar

interferometric synthetic aperture radarInSARSAR interferometry
Volcano and earthquake monitoring is a part of differential interferometry.
This geodetic method uses two or more synthetic aperture radar (SAR) images to generate maps of surface deformation or digital elevation, using differences in the phase of the waves returning to the satellite or aircraft.

Imaging radar

radar imagingradar imageryimaging
A synthetic-aperture radar is an imaging radar mounted on a moving platform.
Current radar imaging techniques rely mainly on synthetic aperture radar (SAR) and inverse synthetic aperture radar (ISAR) imaging.

SAMV (algorithm)

SAMViterative Sparse Asymptotic Minimum Variance
SAMV method is a parameter-free sparse signal reconstruction based algorithm.
Applications include synthetic-aperture radar, computed tomography scan, and magnetic resonance imaging (MRI).

Radar

radar stationradarsradar system
Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes.
Aperture synthesis by post-processing motion data from a single moving source, on the other hand, is widely used in space and airborne radar systems.

Pulse-Doppler radar

Dopplerpulse-Dopplerpulse doppler
(See pulse-doppler radar).
Pulse-Doppler radar is also the basis of synthetic aperture radar used in radar astronomy, remote sensing and mapping.

Beamforming

beam formingbeamformerAntenna beamforming
The pulses are transmitted and the echoes received using a single beam-forming antenna, with wavelengths of a meter down to several millimeters.
Synthetic aperture radar

Speckle noise

speckleImage Despeckling
Unfortunately, the phase differences between adjacent image picture elements ("pixels") also produce random interference effects called "coherence speckle", which is a sort of graininess with dimensions on the order of the resolution, causing the concept of resolution to take on a subtly different meaning.
Speckle is a granular 'noise' that inherently exists in and degrades the quality of the active radar, synthetic aperture radar (SAR), medical ultrasound and optical coherence tomography images.

Analog computer

analogue computeranaloganalog computers
The processor was to be, in effect, an optical analog computer performing large-scale scalar arithmetic calculations in many channels (with many light "rays") at once.
More complex applications, such as synthetic aperture radar, remained the domain of analog computing well into the 1980s, since digital computers were insufficient for the task.

Optical computing

optical computerphotonic computingoptical processor
The "optical data-processors" developed for this radar purpose were the first effective analog optical computer systems, and were, in fact, devised before the holographic technique was fully adapted to optical imaging.
Application-specific devices, such as synthetic aperture radar (SAR) and optical correlators, have been designed to use the principles of optical computing.

Aperture synthesis

aperture synthesis imagingsynthetic apertureinterferometric imaging
Rather than discarding the phase data, information can be extracted from it. If two observations of the same terrain from very similar positions are available, aperture synthesis can be performed to provide the resolution performance which would be given by a radar system with dimensions equal to the separation of the two measurements.
Aperture synthesis is also used by a type of radar system known as synthetic aperture radar, and even in optical telescopes.

Magellan (spacecraft)

MagellanMagellan'' spacecraftMagellan'' (spacecraft)
The Venera 15 and Venera 16 followed later by the Magellan space probe mapped the surface of Venus over several years using synthetic aperture radar.
The Magellan spacecraft, also referred to as the Venus Radar Mapper, was a 1035 kg robotic space probe launched by NASA of the United States, on May 4, 1989, to map the surface of Venus by using synthetic aperture radar and to measure the planetary gravitational field.

Cassini–Huygens

CassiniCassini spacecraftCassini'' spacecraft
The Cassini mission to Saturn used SAR to map the surface of the planet's major moon Titan, whose surface is partly hidden from direct optical inspection by atmospheric haze.
The Italian Space Agency (ASI) provided the Cassini orbiter's high-gain radio antenna, with the incorporation of a low-gain antenna (to ensure telecommunications with the Earth for the entire duration of the mission), a compact and lightweight radar, which also uses the high-gain antenna and serves as a synthetic-aperture radar, a radar altimeter, a radiometer, the radio science subsystem (RSS), the visible channel portion VIMS-V of VIMS spectrometer.

Emmett Leith

Emmett N. Leith
An early analysis by Dr. Louis J. Cutrona, Weston E. Vivian, and Emmett N. Leith of that group showed that such a fully focused system should yield, at all ranges, a resolution equal to the width (or, by some criteria, the half-width) of the real antenna carried on the radar aircraft and continually pointed broadside to the aircraft's path.
Much of Leith's holographic work was an outgrowth of his research on synthetic aperture radar (SAR) performed while a member of the Radar Laboratory of the University of Michigan's Willow Run Laboratory beginning in 1952.

Lacrosse (satellite)

LacrosseLacrosse 1Lacrosse Radar Satellite
The National Reconnaissance Office maintains a fleet of (now declassified) synthetic aperture radar satellites commonly designated as Lacrosse or Onyx.
In July 2008, the NRO itself declassified the existence of its synthetic aperture radar (SAR) satellite constellation.

Titan (moon)

TitanSaturn's moon Titanatmosphere
The Cassini mission to Saturn used SAR to map the surface of the planet's major moon Titan, whose surface is partly hidden from direct optical inspection by atmospheric haze.
The Cassini spacecraft used infrared instruments, radar altimetry and synthetic aperture radar (SAR) imaging to map portions of Titan during its close fly-bys.

Raytheon Sentinel

Sentinel R1ASTORRaytheon Sentinel R.1
In February 2009, the Sentinel R1 surveillance aircraft entered service in the RAF, equipped with the SAR-based Airborne Stand-Off Radar (ASTOR) system.
The main radar is a Raytheon dual-mode synthetic aperture radar / moving target indication (SAR/MTI) radar known as Sentinel Dual Mode Radar Sensor (DMRS).

Phased array

phased array radarphased-arrayphased-array radar
A technique closely related to SAR uses an array (referred to as a "phased array") of real antenna elements spatially distributed over either one or two dimensions perpendicular to the radar-range dimension.
Synthetic-aperture radar

Antenna aperture

apertureaperture efficiencyeffective area
The distance the SAR device travels over a target in the time taken for the radar pulses to return to the antenna creates the large synthetic antenna aperture (the size of the antenna).

Radio wave

radio wavesradioradio signal
To create a SAR image, successive pulses of radio waves are transmitted to "illuminate" a target scene, and the echo of each pulse is received and recorded.

Echo

echoesechoedechoing
To create a SAR image, successive pulses of radio waves are transmitted to "illuminate" a target scene, and the echo of each pulse is received and recorded.

Wavelength

wavelengthsperiodsubwavelength
The pulses are transmitted and the echoes received using a single beam-forming antenna, with wavelengths of a meter down to several millimeters.

Signal processing

signal analysissignalsignal processor
Signal processing of the successive recorded radar echoes allows the combining of the recordings from these multiple antenna positions.