WE3.L10.3: THE FUTURE OF SPACEBORNE SYNTHETIC APERTURE RADAR

A Tribute to the Pioneer Work of Kiyo Tomiyasu
The Future of Spaceborne Synthetic Aperture Radar
G. Krieger, A. Moreira
Microwaves and Radar Institute
German Aerospace Center (DLR)

First Civilian SAR Satellite: Seasat

Launch June 26, 1978 Wavelength 0,235 m
Altitude ~780 km Bandwidth 19 MHz
Weight 2300 kg Antenna 10,74 m x
Size 2,16 m
Incident Angle ~ 23°
Swath Width 100 km Resolution 25 m x 25 m

IGARSS 2010 - Special Session Honoring the Achievements of Kiyo Tomiyasu

SAR Missions since 1978 (selection)

SEASAT ERS-1/2 J-ERS-1 SIR-C/X-SAR
NASA/JPL (USA) European Space Agency (ESA) Japanese Space Agency (NASDA) NASA/JPL, L- and C-Band (quad)
L-Band, 1978 C-Band, L-Band, 1992-1998 DLR / ASI, X-band
1991-2000 & 1995-today April and October 1994

RADARSAT-1 SRTM ENVISAT / ASAR ALOS / PALSAR
Canadian Space Agency (CSA) NASA/JPL (C-Band), DLR (X-Band) European Space Agency (ESA) Japanese Space Agency (JAXA)
C-Band, 1995-today February 2000 C-Band (dual), 2002-today L-Band (quad), 2005

SAR Lupe CosmoSkymed TerraSAR-X RADARSAT-2
BWB Germany ASI / Alenia German Aerospace Center (DLR) / Astrium Canadian Space Agency (CSA)
X-Band, 2006 X-Band (dual), 2007 X-Band (quad), 2007 C-Band (quad), 2007


Earthquakes Volcanoes Land & Sea Ice

Ocean Land Environment Subsidence

Traffic Disaster Reconnaissance


Future SAR Systems: Motivation

Application Areas for SAR Data Future Requirements
Earthquakes Volcanoes Land & Sea Ice • wider coverage and
shorter revisit times
• higher geometric and
radiometric resolution
• new data products from
Ocean Land Environment Subsidence coherent combinations
of SAR images:
- Delta-DEMs
(ice mass balance, ...)
- 3-D volume imaging
Traffic Disaster Reconnaissance (forest structure, ...)
- 4-D tomography
(biomass dynamics, …)
• reliable data supply
• cost efficiency


Future SAR Systems: Motivation

The Many Ingenious Ideas of Kiyo Tomiyasu Future Requirements
• wider coverage and
shorter revisit times
• higher geometric and
radiometric resolution
• new data products from
coherent combinations
of SAR images:
- Delta-DEMs
(ice mass balance, ...)
- 3-D volume imaging
(forest structure, ...)
- 4-D tomography
(biomass dynamics, …)
• reliable data supply
• cost efficiency


(IEEE EASCON, 1978)


TanDEM-X


TanDEM-X Launch, June 21, 2010

First TanDEM-X Interferogram & DEM
(Large Baseline Pursuit Monostatic)

October
Revolution
Island


20 km

38 km of Spaceborne Synthetic Aperture Radar
The Future

hamb = 3 m
Beff = 2.6 km
x = 20 m x 20 m
h  10 cm


hamb = 3 m
Beff = 2.6 km
x = 20 m x 20 m
h  10 cm

• TanDEM-X Special Session:
 Thursday, 8:20 – 10:00 am
• Prats et al., “Taxi: A versatile processing ...,”
 Friday, 9:40 – 10:45 am
• www.dlr.de


Measurement of Height Changes

“Double Differential SAR Interferometry”
e.g. difference between two single-pass cross-track interferograms
pass 1
Bistatic 1
Bistatic
Strip map
Strip map
B ==3000 m
B 3000 m
x ==12 m h(t1)
x 12 m

pass 2
2

h < 10 cm
h(t2)

  h ~ 2 - 1
coherence between
passes not mandatory

 Grounding line detection, vegetation growth, snow/ice accumulation, … ?


Single-Pass InSAR for Ice Monitoring

High uncertainty about future sea level rise
IPCC’07 height increase 28 - 43 cm, now 1.4 m
major uncertainty: stability of polar ice sheets
Large Baseline Single-Pass InSAR
provides high resolution also in complex terrain
avoids gaps of laser & radar altimetry systems
allows accurate observation of temporal evolution
Vorhaben TanDEM-X Nutzung

Single-Pass InSAR for Ice Monitoring

• Börner et al., “SIGNAL: SAR for Ice, Glacier ...”
 Thursday, 9:40 – 10:45 am
High uncertainty about future sea level rise
IPCC’07 height increase 28 - 43 cm, now 1.4 m
major uncertainty: stability of polar ice sheets
Large Baseline Single-Pass InSAR
provides high resolution also in complex terrain
avoids gaps of laser & radar altimetry systems
allows accurate observation of temporal evolution
Vorhaben TanDEM-X Nutzung

Measurement of Polarimetric SAR
Vegetation Height Interferometry
(Pol-InSAR)

m
30
~
Estimation of the vertical structure of volume scatterers:
Vertical structure components are resolved by means
of their polarimetric signature;
The (height) location of the resolved structural
components is estimated by interferometric measurements.


Measurement of 3-D
Vegetation Structure

Combination of Multiple
Single-Pass Interferograms

pass 1 pass k pass N

… …
* * *

Reconstruction of Scattering Profile
(van Cittert-Zernike theorem)


Tomography: A Revolution in Medical Diagnostics and Research


The Next Revolution: Functional Brain Imaging


The Next Revolution: Functional Brain Imaging

4-D SAR Imaging
monitoring internal
structure changes


4-D SAR Imaging
monitoring internal
structure changes
in
forests, ice, snow,
permafrost soils, ...


Use of Compact Antennas

ambiguities Rx 3 Rx 2 Rx 1 Tx

v
P1  f 

P2  f 
ambiguities
suppressed

P3  f 


Multistatic Sparse Array

Linear Beamforming: s3(x,t ) Interferometry:
s2(x,t ) sN (x,t )
• ambiguity s1(x,t ) • cross-track (DEM,
suppression Pol-InSAR)
• wide swath • coherence
imaging tomography
• tomography • along-track (ocean
• MTI (e.g. STAP) currents, MTI)
• super-resolution si ( x,t ) s j ( x,t )
• interference
suppression SAR SAR
SAR
SAR SAR
SAR
s1( x,t ) sN (x,t ) SAR
SAR Proc. SAR
SAR Proc.
Challenge: Proc.
Proc. Proc.
Proc.
Proc.
Proc. Proc.
Proc.
Optimum Combination
N xx
x
h (x,t, x',t' )  s (x',t' )  dx'dt'
Nonlinear Approach x
i i s1( x,t ) sN ( x,t ) x
i 1

f s1( x,t ),..., sN ( x,t )
Interf.
Comb.


Sparse Apertures and Reconfigurable Arrays


Frequent
Monitoring


Kiyo
Tomiyasu

(IEEE Ant. & Prop. Symp., 1978) (IEEE EASCON, 1978)

GEO+LEO
GEO


GEO-LEO SAR: NESZ Example

Wavelength 3.1 cm
Max. Bandwidth 300 MHz
Average Transmit Power 1000 W
Antenna Size Tx 100 m2
Antenna Size Rx 6 m2
Noise Figure + Losses 5 dB
Receiver Altitude 400 km
Ground Resolution 3m
Max. Res. Cell Diameter 6m

nadir-looking
SAR enables
synergy with
other instruments
(e.g. optical sensors,
altimeters, ....)

res< 6m

200 km 200 km 200 km
Br<300MHz


Antenna Footprint Comparison

LEO
er
receiv
te
satelli

Receiver Footprint
  10 km
(X-Band, dant=2m, inc<40°)

Transmitter Footprint
125 km x 250 km
(X-Band, dant=10m, =48°)
transmitter


Multiple Beams on Receive

Tx Rx


Digital Beamforming on Receive

Transmitter
Multiple
Receiver beams
with adaptable
antenna
patterns

Mixing x x x x x

Analog A A A A A
Digital D D D D D
Conversion
Digital
Signal Digital Beam Forming
Processing

Focusing and
Higher-Level SAR Processing
Processing


Global Monitoring

High-Resolution Wide-Swath Imaging
Usage of Tx Power

gain improved by
more than 10 dB


Echolocation
in Bats

19.12.2005 Vortragstitel 38

Pinna Movement for Angular "Scan on Receive"


DBF-SAR with Reflector Antennas



MEOSAR

3 revisits / day
(for 1 satellite)

huge
simultaneous
access area

multi-
frequency
capability
system concept based on
advanced DBF architecture

Adaptive & Cognitive MIMO SAR Systems

maximize information gain for salient features
a given power & data budget

beam trigger

DBF on waveform
receive encoding
Spotlight
Zoom
Wide Area HRWS
Search Stripmap

environment
optimized distribution of system resources of Spaceborne Synthetic Aperture Radar
The Future

Kiyo Tomiyasu

Best wishes and many congratulations!

WE3.L10.3: THE FUTURE OF SPACEBORNE SYNTHETIC APERTURE RADAR

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