ENVISAT ASAR ScanSAR Complex Focusing

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ENVISAT ASAR ScanSAR Complex Focusing
Interferometry
A. Monti Guarnieri Dipartimento
di Elettronica e Informazione - Politecnico di
Milano C. Cafforio, P. Guccione
Dipartimento di Elettronica ed Elettrotecnica -
Politecnico di Bari
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ENVISAT ASAR ScanSAR geometry
ScanSAR is a particular SAR that achieves a very
wide swath coverage by periodically switching
the antenna pointing in several range
subswaths. The sensor acquires for short bursts
by ciclycally scanning all the subswaths
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ScanSAR Wide Swath look computation
Each burst gives a focused look. Looks partially
overlap in time (3 for WSM), but not in
frequency. They are kept separated and will be
averaged at interferogram level.
Frequency (Hz)
Azimuth (ms)
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Wide Swath complex product
Focused ScanSAR Wide Swath data will be arranged
in a new complex product Wide Swath Mode Single
Look Complex (WSM SLC) where attention is paid
particularly to the phase preserving and time
annotations, as focused bursts overlap.
The outputs of an ENVISAT ASAR ScanSAR focusing
processor must be focused bursts (written
sequentially) of all the processed swaths, all
resampled on a coherent sampling grid.
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WSS WSM Complex Product
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WSS WSM Complex Product
ASA_WSS is a single range look (full bandwidth)
phase pres. level-1 product.
It is a collection of bursts / swaths all sampled
on the same grid.
It is intended for interferometry, large scale
analysis and see/ice applications.
It can be post-processed do derive all the other
WSS products.
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Multimode interferometry implementation
MASTER IMAGE
IM/AP pp focused
MMSE Slave Image Reconstruction
Hermitian multiplication look averaging
Differential interferogram
SLAVE IMAGE
MMSE Master Image Reconstruction
IM/AP /WSM
Co-registration
p.p. focusing (WSM)
Coherence map
Interferogram adaptive filtering
Mosaicking Geocoding
Doppler parameters
Synthetic fringes
Co-registering map and Scan pattern.
Ancillary and Orbits
Geocoded Differential Interferogram
Geocoded Coherence Map
Synthetic fringes and geometric
information processor
Full. res. DEM
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WSS Product Computing Time

• ASA__WS0 53000 packets (30 sec) 330 MB (1 byte
  / complex sample)

• CPU Mobile Pentium 1000

• Processor POLIMI/POLIBA Reference Processor
  (0th ord. block w-k dechirping GLS filter
  bank).

• Sampling interval (16 MHz)-1 x 10 ms (7 m x 130
  m) 1 GB (4 byte / complex sample)

• Data extraction preconditioning (FBAQ decoding,
  gain droop, .) 16 min

• Range Focusing 8 min

• Azimuth Focusing 20 x 5 10 m

Total computing time 2 h. Steps () can be
otpimized. Specan focusing gt 30 more efficient.
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Monitoring by IM/WSM InSAR
WSM/IM combination provide frequent
interferometric capability at a good resolution
vs phase accuracy tradeoff. The same baseline
range as for IM/IM can be exploited.
In case that synchronized scans acquisitions
could be programmed, WSM/WSM combinations could
provide large scale interferograms. Small
baselines are mandatory.
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WSM/IM Interferometry
Las Vegas Geocoded phaseampl Bn 35 m.
IS2. WSS 14/3/03, IMS 29/11/02. SRTM DEM
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WSM/IM phase
No scalloping !
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Monitoring by WSM/WSM InSAR
Latitude (o) 0-30 30-55 gt75 Revisit
time (days) 3-4 2-3 lt1 () ascending
descending orbits
In case that synchronized scans acquisitions
could be programmed, WSM/WSM combinations could
provide large scale interferograms. Small
baselines are mandatory.
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Flevoland Phaseampl Bn 400 m. 1/12/02,
5/1/03 Ellipsoid Flattening 400 x 400 km