ScanSAR ScanSAR InterferometryInterferometry

Jeremy WurmlingerJeremy WurmlingerUniversity of KansasUniversity of Kansas

EECS826EECS826Spring 2009Spring 2009

TopicsTopics

ScanSAR overviewScanSAR overviewScanSAR signal propertiesScanSAR signal propertiesScanSAR interferometryScanSAR interferometrySpaceborne satellite ScanSARSpaceborne satellite ScanSARConclusionConclusionQuestions/Comments?Questions/Comments?

ScanSAR overviewScanSAR overview Also known as “Burst mode” or “Wide Swath mode”Also known as “Burst mode” or “Wide Swath mode” Achieves a large swath coverage by periodically switching the antenna look Achieves a large swath coverage by periodically switching the antenna look

angleangle Changing Antenna look angle results in have Multiple SwathChanging Antenna look angle results in have Multiple Swath During the look angle transfer, there is no transmit or receive(off period)During the look angle transfer, there is no transmit or receive(off period) Allows imaging of a wide swath area at the expense of azimuth resolutionAllows imaging of a wide swath area at the expense of azimuth resolution Typical swath widths range from 300km-500kmTypical swath widths range from 300km-500km Raw data consists of bursts of radar echoes that are shorter than the Raw data consists of bursts of radar echoes that are shorter than the

synthetic aperature lengthsynthetic aperature length Various satellites are built with a ScanSAR mode: RADARSAT-1, Various satellites are built with a ScanSAR mode: RADARSAT-1,

RADARSAT-2, PALSAR among others.RADARSAT-2, PALSAR among others.

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ScanSAR overviewScanSAR overview

NNLL=T/T=T/TPP (Burst Look: # of bursts per (Burst Look: # of bursts per synthetic aperture)synthetic aperture)

TTBB=Burst Duration=Burst DurationTTPP=Burst Cycle Period=Burst Cycle PeriodT=Width of Antenna FootprintT=Width of Antenna Footprintθθ11=Look angle for first swath=Look angle for first swathθθ22=Look angle for second swath=Look angle for second swath

NNBB=Sequence of Burst Echo lines=Sequence of Burst Echo lines

NNSS=T=TPP/T/TBB (# of possible subswaths) (# of possible subswaths)

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ScanSAR Signal PropertiesScanSAR Signal Properties

Impulse Response of a point scatterImpulse Response of a point scatter Frequency Spectrum of a point scattererFrequency Spectrum of a point scatterer

Strip-map modeStrip-map mode Strip-map modeStrip-map mode

Burst modeBurst mode Burst modeBurst mode

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ScanSAR Signal PropertiesScanSAR Signal Properties[1]

Top figure-shows the raw data of a single point scatterer in strip modeTop figure-shows the raw data of a single point scatterer in strip modeBottom figure-shows the raw data of the same scatterer in 4-burst modeBottom figure-shows the raw data of the same scatterer in 4-burst mode

ScanSAR Signal PropertiesScanSAR Signal Properties

Time frequency diagram of a single scatterer located at t=tTime frequency diagram of a single scatterer located at t=t00

WB=Burst BandwidthWB=Burst BandwidthWP=Distance between Spectral components of each individual burstWP=Distance between Spectral components of each individual burstWA=Chirp bandwidthWA=Chirp bandwidthHC(f;t0)=Signal Spectrum of the scatterer located at toHC(f;t0)=Signal Spectrum of the scatterer located at to

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ScanSAR Signal PropertiesScanSAR Signal Properties[1]

Figure to the left depicts the impulse response in both strip and burst modeFigure to the left depicts the impulse response in both strip and burst mode

Figure to the right depicts the doppler centroid estimation of a scatterer in 2 Beam burst modeFigure to the right depicts the doppler centroid estimation of a scatterer in 2 Beam burst mode

ScanSAR InterferometryScanSAR Interferometry Multipass ScanSAR images may be used for interferogram Multipass ScanSAR images may be used for interferogram

generation to obtain elevation datageneration to obtain elevation data Several issues present themselves in inteferometric ScanSARSeveral issues present themselves in inteferometric ScanSAR

1. Critical Baseline and Bandwidth 1. Critical Baseline and Bandwidth

1. Doppler Centroid Estimation1. Doppler Centroid Estimation

2. PRF Ambiguity Resolution2. PRF Ambiguity Resolution

3. Azimuth Scanning Pattern Synchronization3. Azimuth Scanning Pattern Synchronization

4. Range Processing4. Range Processing

5. Azimuth Proecssing5. Azimuth Proecssing

6. Interferogram Generation6. Interferogram Generation

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ScanSAR InterferometryScanSAR Interferometry

-Example of RADARSAT-1 datasheets-Example of RADARSAT-1 datasheets used for Interferometryused for Interferometry

-Out of 12 RADARSAT datasets…two-Out of 12 RADARSAT datasets…two pairs existed with baseline shorterpairs existed with baseline shorter than critical baselinethan critical baseline-Out of the 2 datasets, only 1 pair-Out of the 2 datasets, only 1 pair showed acceptable coherenceshowed acceptable coherence

-For DTM purposes, this particular-For DTM purposes, this particular ScanSAR dataset for RADARSATScanSAR dataset for RADARSAT was able to acheive better resolution was able to acheive better resolution than DTED-1than DTED-1

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Burst Mode Image ProductsBurst Mode Image Products

Two Approaches to consider when approaching the phase-preserving dataTwo Approaches to consider when approaching the phase-preserving data

Single-Burst Image- Bursts are processed to individual complex images. The complex Single-Burst Image- Bursts are processed to individual complex images. The complex burst-mode product is then produced by these Burst complex images. Each image burst-mode product is then produced by these Burst complex images. Each image has a resolution to 1/Whas a resolution to 1/WB B and covers an azimuth extent of T-Tand covers an azimuth extent of T-TB. B. One of the One of the inconvenience asssociated with Single-Burst images are their azimuth-variant inconvenience asssociated with Single-Burst images are their azimuth-variant spectral bandpass characteristic. The signal varies linearly with azimuth fromspectral bandpass characteristic. The signal varies linearly with azimuth from

-W-WAA/2 to W/2 to WAA/2 and wraps around several times in the +/- PRF/2 and wraps around several times in the +/- PRFnn/2 band of the burst /2 band of the burst image This excludes the use of standard coregistration and resampling algorithms.image This excludes the use of standard coregistration and resampling algorithms.

Figure to the right shows the time frequency diagram Figure to the right shows the time frequency diagram of focused multiple burst RADARSAT ScanSAR dataof focused multiple burst RADARSAT ScanSAR data

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Burst Mode Image ProductsBurst Mode Image Products

Multiple-Burst Image- involves the coherent superposition of the burst images forming a Multiple-Burst Image- involves the coherent superposition of the burst images forming a single full-aperture image. Suffers the multiple peak shape of figure in the right hand single full-aperture image. Suffers the multiple peak shape of figure in the right hand corner. It has been shown, however that a low-pass filter applied to the multiple-burst corner. It has been shown, however that a low-pass filter applied to the multiple-burst image gives a image comparable to the one obtained by incoherent superposition of image gives a image comparable to the one obtained by incoherent superposition of burst images. The average spectral envelope of such a complex burst image is burst images. The average spectral envelope of such a complex burst image is identical to that of a strip-map mode. Therefore, standard InSAR processing can be identical to that of a strip-map mode. Therefore, standard InSAR processing can be applied to multiple-burst images. The cost of this however is increased data volume.applied to multiple-burst images. The cost of this however is increased data volume.

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Critical Baseline and BandwidthCritical Baseline and Bandwidth

Critical Baselines for RADARSAT modes and ERSCritical Baselines for RADARSAT modes and ERS

-ScanSAR typically operates in a-ScanSAR typically operates in a reduced range chirp bandwidthreduced range chirp bandwidth

-Not only a resolution problem, but-Not only a resolution problem, but also effects the size of the criticalalso effects the size of the critical baselinebaseline

-Core reason why Narrow beam mode-Core reason why Narrow beam mode is preferred when using ScanSAR foris preferred when using ScanSAR for Interferometric purposesInterferometric purposes

(Critical Baseline increases with increase(Critical Baseline increases with increase in incidence angle)in incidence angle)

-A lower range chirp bandwidth also-A lower range chirp bandwidth also requires tighter margins for repeatedrequires tighter margins for repeated orbit trajectoriesorbit trajectories

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Doppler CentroidDoppler Centroid-Since the shape of the doppler spectrum-Since the shape of the doppler spectrum will be distorted in Burst mode….Dopplerwill be distorted in Burst mode….Doppler Centroid estimation is more difficult than Centroid estimation is more difficult than Stripmap mode.Stripmap mode.

Yaw Steering- Antenna mid-beam axis is pointed in the direction of the Yaw Steering- Antenna mid-beam axis is pointed in the direction of the Zero Doppler frequency. This results in the majority of theZero Doppler frequency. This results in the majority of the Doppler Centroid values being the 0Doppler Centroid values being the 0thth PRF band. PRF band.

--Can be achieved by packing the bursts densely Can be achieved by packing the bursts densely

in the azimuth direction, which would give an in the azimuth direction, which would give an

uninterrupted sequence of range lines…then pass uninterrupted sequence of range lines…then pass

through a Doppler Centroid Estimator(same through a Doppler Centroid Estimator(same

as strip mode)as strip mode)

-Allows coregistration parameters to be derived for each individual-Allows coregistration parameters to be derived for each individualswathswath

-Avoids Phase biases due to interferometric misregistration, PRF ambiguity -Avoids Phase biases due to interferometric misregistration, PRF ambiguity resolution,and Beam alignment and baseline estimate become much easierresolution,and Beam alignment and baseline estimate become much easier

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PRF AmbiguityPRF Ambiguity

If a satellite in not yaw-steered, then PRF ambiguity resolution is necessary. Without If a satellite in not yaw-steered, then PRF ambiguity resolution is necessary. Without

the use of Yaw Steering….Doppler Centroid Values exceeding +-PRF/2 are expectedthe use of Yaw Steering….Doppler Centroid Values exceeding +-PRF/2 are expected

Various methods can be applied to compensate for the PRF ambiguity. As discussed Various methods can be applied to compensate for the PRF ambiguity. As discussed in Holzner and Bamler’s, a range look correlation technique is used. Since ScanSAR in Holzner and Bamler’s, a range look correlation technique is used. Since ScanSAR scenes cover areas about 10 times as large strip-map images, it is very likely that scenes cover areas about 10 times as large strip-map images, it is very likely that there are a few point targets in the scene. With the range look correlation, these there are a few point targets in the scene. With the range look correlation, these point-like targets will be automatically detected.point-like targets will be automatically detected.

The figure to the right shows the rangeThe figure to the right shows the rangeCross correlation of two looks of a pointCross correlation of two looks of a pointlike target.like target.

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Azimuth Scanning Pattern SynchronizationAzimuth Scanning Pattern Synchronization

Azimuth Scanning Pattern-azimuth pattern of the sequence of bursts(radar on) and Azimuth Scanning Pattern-azimuth pattern of the sequence of bursts(radar on) and pauses(radar off)pauses(radar off)

Interferogram formation requires that the burst patterns of both datasets be aligned Interferogram formation requires that the burst patterns of both datasets be aligned with each otherwith each other

The goal of Azimuth Scanning Pattern Synchronization is to perserve companions of The goal of Azimuth Scanning Pattern Synchronization is to perserve companions of raw data lines of the same ground area located in your image.raw data lines of the same ground area located in your image.

poses a problem when trying to perform interferometric processingposes a problem when trying to perform interferometric processing Another reason why narrow beam ScanSAR is preferred over wide beam ScanSAR. Another reason why narrow beam ScanSAR is preferred over wide beam ScanSAR.

Figure to the right shows the variation of interferogram Figure to the right shows the variation of interferogram peak values vs mutual azimuth shift. The large peakpeak values vs mutual azimuth shift. The large peakindicates a high ASPS. The figure was formed fromindicates a high ASPS. The figure was formed fromthe method discussed on next slide.the method discussed on next slide.

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Azimuth Scanning Pattern SynchronizationAzimuth Scanning Pattern Synchronization

Pre-Processing MethodPre-Processing Method1.1. Small azimuth portion of both image datasets is takenSmall azimuth portion of both image datasets is taken2.2. Mutual azimuth shift is estimated from the two imagesMutual azimuth shift is estimated from the two images3.3. Co-registration of the two datasets(accuracy to 1 range line)Co-registration of the two datasets(accuracy to 1 range line)4.4. Only the range lines that related in for both datasets are kept Only the range lines that related in for both datasets are kept

for further processing; the rest are discarded.for further processing; the rest are discarded.

The more in sync the burst cycles of each dataset are with The more in sync the burst cycles of each dataset are with each other, the finer the final azimuth resolution of the each other, the finer the final azimuth resolution of the interferometric image will be.interferometric image will be.

““Mutually exclusive”-on cycles of one dataset line up with off Mutually exclusive”-on cycles of one dataset line up with off cycles of the second datasetcycles of the second dataset

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Range ProcessingRange Processing

Two methods of Range Processing are but not limited to:Two methods of Range Processing are but not limited to:

-Single Burst Range Processing-Single Burst Range Processing

-Pack and Go Range Processing(proposed by Holzner and Balmer)-Pack and Go Range Processing(proposed by Holzner and Balmer)

Single Burst Range ProcessingSingle Burst Range Processing-Each burst of range lines is processed -Each burst of range lines is processed separately by a standard processor whose azimuth compression has been separately by a standard processor whose azimuth compression has been disabled. This method is computationally efficient, however, often the bursts disabled. This method is computationally efficient, however, often the bursts must be supplemented by a number of range lines containing zeroes to the must be supplemented by a number of range lines containing zeroes to the next power of two.next power of two. [1]

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Range ProcessingRange Processing

Pack & Go Range ProcessingPack & Go Range Processing-Since during range processing (almost) no energy leakage -Since during range processing (almost) no energy leakage in azimuth occurs, several bursts can be concatenated (with a few zero-lines as in azimuth occurs, several bursts can be concatenated (with a few zero-lines as “safety margins” separating the different bursts) and processed simultaneously by the “safety margins” separating the different bursts) and processed simultaneously by the standard SAR processor.. This method is more efficient than single-burst processing, standard SAR processor.. This method is more efficient than single-burst processing, since arbitrarily long FFTs can be used and zero padding (to meet the power-of-two since arbitrarily long FFTs can be used and zero padding (to meet the power-of-two requirement) is negligible. Existing strip-map SAR processors can be used like a requirement) is negligible. Existing strip-map SAR processors can be used like a black box, no matter how large their internally used azimuth processing blocks are. black box, no matter how large their internally used azimuth processing blocks are. Also Doppler centroid estimation that uses large estimation windows can be Also Doppler centroid estimation that uses large estimation windows can be conveniently applied to this packed burst dataset.conveniently applied to this packed burst dataset.

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Azimuth ProcessingAzimuth ProcessingA focused burst image exhibits a range-dependent azimuth sample spacing known as fan-shape A focused burst image exhibits a range-dependent azimuth sample spacing known as fan-shape distortion. When performing Azimuth processing, an additional interpolation step is required.distortion. When performing Azimuth processing, an additional interpolation step is required.

Azimuth Variant Filtering Azimuth Variant Filtering -After-After a burst has been range processed, standard azimuth compression is a burst has been range processed, standard azimuth compression is applied. The result is a coherent superposition of several shifted replicas of the desired burst applied. The result is a coherent superposition of several shifted replicas of the desired burst image.A time-domain azimuth band-pass filter whose center frequency varies with azimuth position image.A time-domain azimuth band-pass filter whose center frequency varies with azimuth position is required finally to separate the correct result from the aliased one.is required finally to separate the correct result from the aliased one.

Extend Chirp ScalingExtend Chirp Scaling- One method used to avoid the fan-shape distortion and the additional - One method used to avoid the fan-shape distortion and the additional interpolation step could be done by using a high precision ECS algorithm, which would use the interpolation step could be done by using a high precision ECS algorithm, which would use the standard SPECAN method for the azimuth processing and the chirp scaling for accurate range standard SPECAN method for the azimuth processing and the chirp scaling for accurate range processing. Adding a azimuth scaling step would also equalize the frequency rates of the azimuth processing. Adding a azimuth scaling step would also equalize the frequency rates of the azimuth chirps.chirps.

Time-Domain Azimuth CorrelationTime-Domain Azimuth Correlation-Since the bursts are usually short, a straightforward time-domain -Since the bursts are usually short, a straightforward time-domain azimuth correlation is an alternative to frequency domain methods. Although not as efficient, it is azimuth correlation is an alternative to frequency domain methods. Although not as efficient, it is most easily implemented and allows for a free choice of the output sample spacing.most easily implemented and allows for a free choice of the output sample spacing.

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Phase Preserving Burst Mode ProcessingPhase Preserving Burst Mode Processing

Single Burst ImagesSingle Burst Images-Burst Images acquired from each -Burst Images acquired from each passpass-Individual Burst interferograms formed-Individual Burst interferograms formed-Arrangement of Burst interferograms -Arrangement of Burst interferograms to form subswath interferogramsto form subswath interferograms-Arrange subswath interferograms to -Arrange subswath interferograms to form Nform NLL interferograms interferograms

Multiple Burst ImagesMultiple Burst Images-Multiple Burst images are stored-Multiple Burst images are stored-Coherently add each individual burst -Coherently add each individual burst image from each pass over the target image from each pass over the target area.area.-Interferogram formation-Interferogram formation-Low-Pass filter-Low-Pass filter-N-NLL interferogram is formed interferogram is formed

Final Interferogram formation essentially equivalent whetherFinal Interferogram formation essentially equivalent whetherfrom Single Burst method or Multiple Burst Methodfrom Single Burst method or Multiple Burst Method

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Single-Burst Interferogram MethodSingle-Burst Interferogram Method

Arrange subwath interferogramsArrange subwath interferogramsto obtain the Nto obtain the NLL interferogram interferogram

Subwath Inteferogram formed Subwath Inteferogram formed by coherent addition of each by coherent addition of each burst interferogramburst interferogram

Companion Burst ImagesCompanion Burst Imagesacquired from each pass acquired from each pass Individual ‘Burst’ InterferogramsIndividual ‘Burst’ Interferogramsare formedare formed

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Multi-Burst Interferogram MethodMulti-Burst Interferogram Method

Multiple Burst images areMultiple Burst images arestored for each Pass(N=3)stored for each Pass(N=3)

Coherent addition of eachCoherent addition of eachindividual burst image fromindividual burst image fromeach pass to form a multiple each pass to form a multiple burst imageburst image

Interferogram is formedInterferogram is formed

Low-Pass filteringLow-Pass filteringNNLL interferogram is formed interferogram is formed

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Multi-LookingMulti-LookingFor the generation of subswath interferograms, the singleburst interferograms are For the generation of subswath interferograms, the singleburst interferograms are coherently mosaicked. Straightforward multi-looking requires that the bursts are coherently mosaicked. Straightforward multi-looking requires that the bursts are processed to the same grid within and across beams. Usually, the PRFs in the processed to the same grid within and across beams. Usually, the PRFs in the individual beams differ; hence, the raw data echo lines of the bursts within one swath individual beams differ; hence, the raw data echo lines of the bursts within one swath are not acquired on a continuous integer pixel grid. The ScanSAR processor should are not acquired on a continuous integer pixel grid. The ScanSAR processor should arrange the data on a common reference grid to facilitate further processing. arrange the data on a common reference grid to facilitate further processing. Differential interferograms generated between bursts within one subswath can be Differential interferograms generated between bursts within one subswath can be used to identify phase and sampling errors.used to identify phase and sampling errors.[2]

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Re-SamplingRe-SamplingMutual registration of the interferometric partners requires interpolation of the signal Mutual registration of the interferometric partners requires interpolation of the signal at inter-pixel positions. For multiple and single-burst images sampled at the at inter-pixel positions. For multiple and single-burst images sampled at the acquisition PRF, conventional interpolation methods can be applied since at the large acquisition PRF, conventional interpolation methods can be applied since at the large PRF, the average burst signal spectrum resembles the one of strip-map data PRF, the average burst signal spectrum resembles the one of strip-map data

Depending on the sampling frequency, single-burst image re-sampling has to account Depending on the sampling frequency, single-burst image re-sampling has to account for the azimuth variant band-pass behavior of the signal.for the azimuth variant band-pass behavior of the signal.

Technique proposed Holzner and Technique proposed Holzner and BamlerBamler1. Burst Signal is de-ramped by a quadratic phase function in the 1. Burst Signal is de-ramped by a quadratic phase function in the

time domain such that a low pass signal is obtained time domain such that a low pass signal is obtained 2. The low pas signal is then re-sampled using standard interpolation algorithm2. The low pas signal is then re-sampled using standard interpolation algorithm

3. The Quadratic phase is removed for further processing3. The Quadratic phase is removed for further processing

Alternative approach would be to apply azimuth-varying band pass for resampling.Alternative approach would be to apply azimuth-varying band pass for resampling.

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Beam AlignmentBeam Alignment

The swath interferograms can be either processed to individual DEMs or The swath interferograms can be either processed to individual DEMs or first combined to a full-swath interferogram and then processed to a single first combined to a full-swath interferogram and then processed to a single DEM. The swath overlap region provides valuable information on swath DEM. The swath overlap region provides valuable information on swath registration and mutual phase offsets of the interferograms.registration and mutual phase offsets of the interferograms.

Swath co-registration can be verified by cross-correlation of homologous Swath co-registration can be verified by cross-correlation of homologous patches on an image contrast basis. Misalignment in range will not only patches on an image contrast basis. Misalignment in range will not only disturb topographic information after swath interferogram combination but disturb topographic information after swath interferogram combination but also generates a phase offset owing to the dominant (“flat earth”) fringe also generates a phase offset owing to the dominant (“flat earth”) fringe frequency of the swath interferograms. High Doppler centroid values, frequency of the swath interferograms. High Doppler centroid values, together with tiny misregistration of the interferometric partners will generate together with tiny misregistration of the interferometric partners will generate slowly varying phase errors that also affect the overlap area of the swath slowly varying phase errors that also affect the overlap area of the swath interferograms.interferograms.

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Satellite Orbit DriftSatellite Orbit Drift

Satellite Orbit Data, such as RADARSAT, can have low accuracy. ScanSAR Satellite Orbit Data, such as RADARSAT, can have low accuracy. ScanSAR interferometry is optimal under certains conditions. interferometry is optimal under certains conditions.

For RADARSAT-1 The westward drift lies within ±4 km, and the orbit boosts occurFor RADARSAT-1 The westward drift lies within ±4 km, and the orbit boosts occur

approximately every 35 days. The minimum drift rate of the satellite occurs halftime approximately every 35 days. The minimum drift rate of the satellite occurs halftime between boosts at the drift maximum. Acquisitions around this minimum drift rate are between boosts at the drift maximum. Acquisitions around this minimum drift rate are favorable for ScanSAR interferometry since baselines are expected to be within the favorable for ScanSAR interferometry since baselines are expected to be within the critical baseline.critical baseline.

Alternatively, Orbit Correction can be split into two tasks.Alternatively, Orbit Correction can be split into two tasks.

1.1. Correct the primary channel orbit for shifts in slant range and azimuth directionCorrect the primary channel orbit for shifts in slant range and azimuth direction

2.2. Correcting the secondary channel optimize the baseline length and orbit angle.Correcting the secondary channel optimize the baseline length and orbit angle.

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Satellite Orbit DriftSatellite Orbit Drift

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ScanSAR interferogramsScanSAR interferograms[2]

ScanSAR interferogramsScanSAR interferograms[2]

RADARSAT-1RADARSAT-1RADARSAT-1 was launched at 14h22 on November 4, 1995 from Vandenberg AFB in California, into a sun-RADARSAT-1 was launched at 14h22 on November 4, 1995 from Vandenberg AFB in California, into a sun-synchronous orbit(dawn-dusk) above the Earth with an altitude of 798 kilometers and inclination of 98.6 degrees. synchronous orbit(dawn-dusk) above the Earth with an altitude of 798 kilometers and inclination of 98.6 degrees. Developed under the management of the CSA in cooperation with Canadian provincial governments and the Developed under the management of the CSA in cooperation with Canadian provincial governments and the private sector, it provides images of the Earth for both scientific and commercial applications. private sector, it provides images of the Earth for both scientific and commercial applications.

NASA provided the Delta II rocket to launch RADARSAT-1 in exchange for access to its data. Estimates are that NASA provided the Delta II rocket to launch RADARSAT-1 in exchange for access to its data. Estimates are that the project, excluding launch, cost $620 million (Canadian). The Canadian federal government contributed about the project, excluding launch, cost $620 million (Canadian). The Canadian federal government contributed about $500 million, the four participating provinces (Quebec, Ontario, Saskatchewan, and BC) about $57 million, and $500 million, the four participating provinces (Quebec, Ontario, Saskatchewan, and BC) about $57 million, and the private sector about $63 millionthe private sector about $63 million

It C-Band satellite that operates at 5.3GHz and has the ability of a ScanSAR mode that provides potential swath It C-Band satellite that operates at 5.3GHz and has the ability of a ScanSAR mode that provides potential swath widths up to 500km. While it used to achieve high quality images of the earth, it has the flexibility to support widths up to 500km. While it used to achieve high quality images of the earth, it has the flexibility to support specific requirements. specific requirements.

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RADARSAT-1RADARSAT-1 The RADARSAT-1 SAR utilizes beam forming techniques in order to provide several different The RADARSAT-1 SAR utilizes beam forming techniques in order to provide several different

beam modes. The modes may be capable of imaging closer to or farther from the satellite, with beam modes. The modes may be capable of imaging closer to or farther from the satellite, with finer resolution and accordingly smaller areas or wide areas with worse resolution. finer resolution and accordingly smaller areas or wide areas with worse resolution.

RADARSAT-1 ScanSAR mode actually combines a few of these other modes in order to obtain a RADARSAT-1 ScanSAR mode actually combines a few of these other modes in order to obtain a very wide swath - approximately 500 km, depending on which ScanSAR sub-mode is chosen. very wide swath - approximately 500 km, depending on which ScanSAR sub-mode is chosen. Three resolutions are provided: 75, 150, and 600 metersThree resolutions are provided: 75, 150, and 600 meters

ScanSAR(Narrow mode)ScanSAR(Narrow mode) -~250km nadir offset-~250km nadir offset -~400km nadir offset-~400km nadir offset -Swath width: 300km-Swath width: 300km -Range Resolution: 50m-Range Resolution: 50m -Azimuth Resolution: 50m-Azimuth Resolution: 50m -Look(s): 2-4-Look(s): 2-4 -Incidence Angle: 20-40-Incidence Angle: 20-40°,32-46°°,32-46° °

ScanSAR(Wide mode)ScanSAR(Wide mode) -~250km nadir offset-~250km nadir offset -Swath width: 500km,440km-Swath width: 500km,440km -Range Resolution: 100m-Range Resolution: 100m -Azimuth Resolution: 100m-Azimuth Resolution: 100m -Look(s): 4-8-Look(s): 4-8 -Incidence Angle: 20-50°-Incidence Angle: 20-50°

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RADARSAT-2RADARSAT-2 RADARSAT-2 was successfully launched on December 14 of 2007 for the CSA by Starsem, using a Soyuz FG RADARSAT-2 was successfully launched on December 14 of 2007 for the CSA by Starsem, using a Soyuz FG

launch vehicle. It was developed to be a follow-on to RADARSAT-1. It has the same orbit (798Km orbit) and is launch vehicle. It was developed to be a follow-on to RADARSAT-1. It has the same orbit (798Km orbit) and is separated by half an orbit period from RADARSAT-1. Also operating in C-band, RADARSAT-2 was designedseparated by half an orbit period from RADARSAT-1. Also operating in C-band, RADARSAT-2 was designed

to support all existing RADARSAT-1modes and offers higher quality features ranging from improvement in to support all existing RADARSAT-1modes and offers higher quality features ranging from improvement in resolution, to full flexibility in the selection of polarization options.resolution, to full flexibility in the selection of polarization options.

Key Features and BenefitsKey Features and Benefits-C-Band(5.405GHz)-C-Band(5.405GHz)-3-100 meter resolution-3-100 meter resolution-HH,HV,VV,VH channel polarization-HH,HV,VV,VH channel polarization-Left and Right Looking operation-Left and Right Looking operation-Solid-State Recorders-Solid-State Recorders-On-Board GPS receivers-On-Board GPS receivers-Yaw-Steering capable-Yaw-Steering capable-Reduced programing lead time-Reduced programing lead time-Rapid tasking and priority programming levels-Rapid tasking and priority programming levels-Improved processing abilities and speed-Improved processing abilities and speed

-ScanSAR Wide-500km swath width-ScanSAR Wide-500km swath width 100m*100m resolution100m*100m resolution 20-4920-49° incidence angle° incidence angle Single or Dual polariztionSingle or Dual polariztion

-ScanSAR Narrow-300km swath width-ScanSAR Narrow-300km swath width 50m*50m resolution50m*50m resolution 20-46° incidence angle20-46° incidence angle Single or Dual polarizationSingle or Dual polarization

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RADARSAT-2RADARSAT-2RADARSAT-2 ScanSAR Wide Mode(VV,VH) Brazil, March 3,2008

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RADARSAT-2RADARSAT-2RADARSAT-2 ScanSAR Narrow Mode(VV,VH)Thunder Bay, Ontario, Canada March 3rd 2008[15]

ALOS PALSARALOS PALSARThe Advanced Land Observing Satellite (ALOS), launched on 24 January 2005, is a The Advanced Land Observing Satellite (ALOS), launched on 24 January 2005, is a joint project between JAXA and the Japan Resources Observation System joint project between JAXA and the Japan Resources Observation System Organization (JAROS). ALOS has three remote-sensing instruments: the Organization (JAROS). ALOS has three remote-sensing instruments: the Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) for digital Panchromatic Remote-sensing Instrument for Stereo Mapping (PRISM) for digital elevation mapping, the Advanced Visible and Near Infrared Radiometer type 2 elevation mapping, the Advanced Visible and Near Infrared Radiometer type 2 (AVNIR-2) for precise land coverage observation, and the Phased Array type L-band (AVNIR-2) for precise land coverage observation, and the Phased Array type L-band Synthetic Aperture Radar (PALSAR) for day-and-night and all-weather land Synthetic Aperture Radar (PALSAR) for day-and-night and all-weather land observation. observation.

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ALOS PALSARALOS PALSAR

With a wavelength of 23.6cm, PALSAR can obtain swath widths up to 350km while With a wavelength of 23.6cm, PALSAR can obtain swath widths up to 350km while retaining a spatial resolution of 71-157m*100m(az) at 5 scan, short burst.retaining a spatial resolution of 71-157m*100m(az) at 5 scan, short burst.

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Shuttle Radar Topography Mission(SRTM)Shuttle Radar Topography Mission(SRTM)

In February of 2000, the space shuttle Endeavor carried a specially In February of 2000, the space shuttle Endeavor carried a specially modified Radar system on a 11 day mission.modified Radar system on a 11 day mission.

Obtained elevation data on a near-global scale to generate the most Obtained elevation data on a near-global scale to generate the most complete high resolution digital topographic database of the earth.complete high resolution digital topographic database of the earth.

Only the use of ScanSAR interoferometry made it possible to map Only the use of ScanSAR interoferometry made it possible to map 80% of the earth’s landmass.80% of the earth’s landmass.

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Shuttle Radar Topography Mission(SRTM)Shuttle Radar Topography Mission(SRTM)

C-Band Antenna used Four Beam ScanSAR narrow mode to form 225km swath widthsC-Band Antenna used Four Beam ScanSAR narrow mode to form 225km swath widths Illuminated two subswaths at a time using orthogonal polarizationsIlluminated two subswaths at a time using orthogonal polarizations By use of it’s polarimetric abilities, the ScanSAR duty cycle was 2:1 rather than 4:1By use of it’s polarimetric abilities, the ScanSAR duty cycle was 2:1 rather than 4:1 The X-band antenna did not have steering cababilities and has to operate at a fixed nadir look The X-band antenna did not have steering cababilities and has to operate at a fixed nadir look

angle of 52angle of 52° and swath width of about 45km° and swath width of about 45km The X-band antenna was able to provide higher relative height accuracies by a factor of 2; but The X-band antenna was able to provide higher relative height accuracies by a factor of 2; but

could not come close to the coverage that the C-Band ScanSAR was able to providecould not come close to the coverage that the C-Band ScanSAR was able to provide

[18]

Shuttle Radar Topography Mission(SRTM)Shuttle Radar Topography Mission(SRTM) To obtain the DTM data the system was equipped with two antennas.To obtain the DTM data the system was equipped with two antennas. One antenna was located inside the payload bay of the shuttle, while the other was One antenna was located inside the payload bay of the shuttle, while the other was

located on one end of a 200ft mast that extended from the payload out into space.located on one end of a 200ft mast that extended from the payload out into space. Terrain Data that was mapped was located between Terrain Data that was mapped was located between

60 degrees North latitude and 54 degrees south latitude.60 degrees North latitude and 54 degrees south latitude.

Shuttle Radar Topography Mission(SRTM)Shuttle Radar Topography Mission(SRTM)[18]

Shuttle Radar Topography Mission(SRTM)Shuttle Radar Topography Mission(SRTM)

SRTM main antennaSRTM main antenna

-Consists of two antennas: X-band and C-band-Consists of two antennas: X-band and C-band-C-Band Antenna used for the SRTM mission-C-Band Antenna used for the SRTM mission-Both Transmit and receive antenna-Both Transmit and receive antenna-5.6cm wavelength-5.6cm wavelength-225km swath width-225km swath width

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Shuttle Radar Topography Mission(SRTM)Shuttle Radar Topography Mission(SRTM)SRTM outboard antennaSRTM outboard antenna

-Consists of: X-Band and C-Band antennas, two GPS antennas, -Consists of: X-Band and C-Band antennas, two GPS antennas, LED targets,and a corner cube reflectorLED targets,and a corner cube reflector-Only receive antenna; main antenna used for transmit-Only receive antenna; main antenna used for transmit-mast was extended ~60m from the main antenna-mast was extended ~60m from the main antenna

[18]

ConclusionConclusion

The future of InSAR is highly dependent upon the ScanSAR interferometry and the The future of InSAR is highly dependent upon the ScanSAR interferometry and the continued launch of satellites with ScanSAR capabilites. While sacrificing spatial continued launch of satellites with ScanSAR capabilites. While sacrificing spatial resolution for swath width is the cost of ScanSAR, future technology and processing resolution for swath width is the cost of ScanSAR, future technology and processing continues to grow and show finer resolutions with each new spaceborne satellite. The continues to grow and show finer resolutions with each new spaceborne satellite. The ability to produce DEMs on a World wide coverage in a minimial amount of time is a ability to produce DEMs on a World wide coverage in a minimial amount of time is a highly valuable resource. Which is one of the reasons why ScanSAR mode has highly valuable resource. Which is one of the reasons why ScanSAR mode has become a standard SAR mode on current and future spaceborne satellite missions.become a standard SAR mode on current and future spaceborne satellite missions.

As discussed, the ScanSAR interferometry introduces many complications that the As discussed, the ScanSAR interferometry introduces many complications that the standard strip map mode does not have. The variations in the methods and standard strip map mode does not have. The variations in the methods and processes used to work around this complications are not defined and are up to theprocesses used to work around this complications are not defined and are up to the

Individual on how they would like to process that data. New algorithms and Individual on how they would like to process that data. New algorithms and processing techniques are being continuously to achieve the finer resolutions at the processing techniques are being continuously to achieve the finer resolutions at the higher swath widths.higher swath widths.

QUESTIONS/COMMENTS?QUESTIONS/COMMENTS?

ReferencesReferences[1]Bamler, Richard and Holzner, Jurgen, “Burst-Mode and ScanSAR Interferometry”, [1]Bamler, Richard and Holzner, Jurgen, “Burst-Mode and ScanSAR Interferometry”, IEEE Transactions on IEEE Transactions on Geoscience and Remote SensingGeoscience and Remote Sensing, Vol 40, No. 9, September 2002, Vol 40, No. 9, September 2002[2]Bamler, Richard and Holzner, Jurgen, “ScanSAR Interferometry for RADARSAT -2&3”, [2]Bamler, Richard and Holzner, Jurgen, “ScanSAR Interferometry for RADARSAT -2&3”, Can. J. Remote Can. J. Remote SensingSensing, Vol 30, No. 3, pp. 437-447, 2004, Vol 30, No. 3, pp. 437-447, 2004[3]Bamler, Richard and Holzner, Jurgen, “RADARSAT ScanSAR Interferometry”, [3]Bamler, Richard and Holzner, Jurgen, “RADARSAT ScanSAR Interferometry”, Geoscience and Remote Geoscience and Remote Sensing Symposium, 1999. IGARSS ’99 ProceedingsSensing Symposium, 1999. IGARSS ’99 Proceedings , Vol 3, July 1999, Vol 3, July 1999[4]Guarnieri, Andrea Monti and Prati, Claudo, “ScanSAR Focusing and Interferometry”, [4]Guarnieri, Andrea Monti and Prati, Claudo, “ScanSAR Focusing and Interferometry”, IEEE Transactions on IEEE Transactions on Geoscience and Remote SensingGeoscience and Remote Sensing, Vol 34, No. 4, July 1996, Vol 34, No. 4, July 1996[5]Jin, Michael, “Optimal Range and Doppler Centroid Estimation for a ScanSAR System”, [5]Jin, Michael, “Optimal Range and Doppler Centroid Estimation for a ScanSAR System”, IEEE Transactions on IEEE Transactions on Geoscience and Remote SensingGeoscience and Remote Sensing, Vol 34, No. 2, pp. 479-488, March 1996, Vol 34, No. 2, pp. 479-488, March 1996[6]Tomiyasu,Kiyo,”Conceptual Performance of a Satellite Borne Wide Swath Synthetic Aperature Radar”, [6]Tomiyasu,Kiyo,”Conceptual Performance of a Satellite Borne Wide Swath Synthetic Aperature Radar”, IEEE IEEE Transactions on Geoscience and Remote SensingTransactions on Geoscience and Remote Sensing , Vol GGE-19, No. 2, pp. 108-118, April 1981, Vol GGE-19, No. 2, pp. 108-118, April 1981[7]Shimada, M.A.R and Watanabe Manabe, “ALOS PALSAR: Technical Outline and mission concepts”, 4[7]Shimada, M.A.R and Watanabe Manabe, “ALOS PALSAR: Technical Outline and mission concepts”, 4 thth International Symposium on Retrieval of Bio- and Geophysical Parameters from SAR Data for Land Applications”, International Symposium on Retrieval of Bio- and Geophysical Parameters from SAR Data for Land Applications”, Innsbruck, Austria, Nov 16-19,2004Innsbruck, Austria, Nov 16-19,2004[8]Bamler, Richard,”The SRTM Mission: A World-Wide 30m Resolution DEM from SAR Interferometry in 11 [8]Bamler, Richard,”The SRTM Mission: A World-Wide 30m Resolution DEM from SAR Interferometry in 11 Days”, Photogrammetric Week ’99’, 1999Days”, Photogrammetric Week ’99’, 1999[9][9]http://earth.esa.int/dragon/symp2008/proceedings/38jia.pdfhttp://earth.esa.int/dragon/symp2008/proceedings/38jia.pdf[10][10]http://www.asc-csa.gc.ca/eng/satelliteshttp://www.asc-csa.gc.ca/eng/satellites[11][11]http://cct.rncan.gc.ca/radar/spaceborne/radarsat1/specs/radspec_e.phphttp://cct.rncan.gc.ca/radar/spaceborne/radarsat1/specs/radspec_e.php[12][12]http://envisat.esa.int/handbooks/asar/CNTR2-6-1-2-4-2.htmhttp://envisat.esa.int/handbooks/asar/CNTR2-6-1-2-4-2.htm[13][13]http://www.imagingnotes.com/ee_assets/2008_fall/radarsat-2-f06.jpghttp://www.imagingnotes.com/ee_assets/2008_fall/radarsat-2-f06.jpg[14][14]http://www.radarsat2.info/images/gallery/RSAT-2_ScanSAR_Brazil.jpghttp://www.radarsat2.info/images/gallery/RSAT-2_ScanSAR_Brazil.jpg[15][15]http://www.radarsat2.info/images/gallery//RSAT-2_ScanRAR_Thunder_Bay.jpghttp://www.radarsat2.info/images/gallery//RSAT-2_ScanRAR_Thunder_Bay.jpg[16][16]http://www.palsar.ersdac.or.jp/http://www.palsar.ersdac.or.jp/[17][17]http://earth.esa.int/object/index.cfm?fobjectid=5198http://earth.esa.int/object/index.cfm?fobjectid=5198[18[18]]http://www2.jpl.nasa.gov/srtm/radaroverview.htmlhttp://www2.jpl.nasa.gov/srtm/radaroverview.html