TerraSAR-X & TanDEM-X
Transcript of TerraSAR-X & TanDEM-X
1Microwaves and Radar Institute > 07.06.2006
Wolfgang Keydel & Alberto MoreiraMicrowaves and Radar Institute,
German Aerospace Research Center (DLR), D-82230 Oberpfaffenhofen, Germany
Tel.: +49-8152-980 523; 49-8153-28 2305; e-mails: [email protected]; [email protected]
two Innovative Remote Sensing Starsfor Space-borne Earth Observation
TerraSAR-X & TanDEM-X
VU 2 > Alberto MoreiraMicrowaves and Radar Institute > 07.06.2006
TerraSAR-XA National Science Mission with Commercial Potential
DLR- Project Management- G/S Development & Ops- Science Coordination
Infoterra- Service Infrastructure- Information Products- Commercial Exploitation
Public Private Partnership
Main Mission Goals:• Provision of TerraSAR-X data for scientific applications public interest• Commercial exploitation of TerraSAR-X data by industry
EADS Astrium- Platform Development- Instrument Development- Launch on Dnepr (2006)
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TerraSAR-XApplication Areas
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center frequency 9.65 GHz (X-band)Tx bandwidth up to 150 MHz (300 exp.)PRF 3 KHz to 6,5 KHztransmit duty cycle 13-20%radiated peak power 2260 Wsystem noise figure 5 dB
VU 5 > Alberto MoreiraMicrowaves and Radar Institute > 07.06.2006
antenna dimension in azimuth 4.784 mantenna dimension in elevation 0.704 mazimuth beamwidth 0.33°elevation beamwidth 2.3°scan angle azimuth ± 0.75°scan angle elevation ± 19.2°
VU 6 > Alberto MoreiraMicrowaves and Radar Institute > 07.06.2006
TerraSAR-X Orbit
sunlight sidenight side
dusk/down orbitaltitude at equator 514.8 km inclination 97.44°sun-synchronous repeat orbit:repeat period 11 daysrevisit time: 4.5 days (100%)
2.5 days (95%)orbits per day 15 2/11
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TerraSAR-X Mission Profile
DLR GS Neustrelitz
S-BandTM & TC
Mission Operations
DLR Oberpfaffenhofen
Raw DataAcquisition
DLR GS Weilheim
X-Band Downlink 300 Mbit/sec
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Stripmap Mode
ScanSAR Mode
Spotlight Mode (Sliding)
HighRes Spotlight Mode (Sliding)
TerraSAR-X Imaging ModesFlight direction
Nadir Track
45°
20°
SwathWidth100 km
Stripmap ScanSAR Spotlight HighRes Spotlight
full perf. inc, angle range 20° - 45° 20° - 45° 20° - 55° 20° - 55° scene size along track acqu. length acqu. length 10 km 5 km scene size ground range 30 km 100 km 10 km 10 km single look az. resolution 3 m 16 m 2 m 1 m single look range resolution 3 m (ground) 16 m (ground)
@ 5 looks 1.2 m (slant) 1.2 m (slant)
Centre of rotation
Θ1=20o Θ2=55o
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TerraSAR-X
TD-X
TanDEM-XTerraSAR add-on for Digital Elevation Measurements
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Primary Mission Goal:Generation of a global HRTI-3 DEM
DTE
D/H
RTI
Lev
el
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SRTM / X-SAR E-SAR
DTED-2 HRTI-3
Comparison of DTED/HRTI-Levels: Example
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Applications of Cross-Track Interferometry
Topography Navigation Urban Areas
Crisis Management Glaciology Oceanography
Geology Hydrology Land Use
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TanDEM–X HRTI-3 Spezification
relative vertical accuracy 2 m (90% linear point-to-point error over 1° x 1° cell), absolute vertical accuracy 10 m (90% linear error), absolute horizontal accuracy 10 m (90% circular error), post spacing 12 m x 12 m
TanDEM-X provides a configurable SAR Interferometry Platform for
Demonstrating new SAR Techniques & Applications
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New
SA
R T
echn
ique
s
RxθTxθ
φ
RxθTxθ
φ
ReceiverTransmitter ReceiverTransmitter
64 km/h
56 km/h
68 km/h
Ocean Currents Traffic Monitoring Glacier Mass Balance
Bi-Static SAR Polarimetric InSAR Digital Beamforming
InSAR Processing Super Resolution Formation Flying
Alo
ng-T
rack
Inte
rfer
omet
ryApplications ATI & New Techniques
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TerraSAR - X versus Tandem - X
SAR System Parameters of both Systems fully compatibleallowing both
Independent TanDEM-X Operation in a Monostatic ModeSynchronised Operation in a Bistatic Mode
Main DifferencesMore sophisticated Propulsion System of TanDEM-X allows for Constellation ControlAdditional S-band Receiver enables for Reception of Status & GPS Position Information broadcast by TerraSAR-X X-band Inter-Satellite Link for Phase Referencing between both Radars (resp. Modifications on TerraSAR-X already implemented).
1Microwaves and Radar Institute > 07.06.2006
Calibration Conceptfor Multiple Mode High Resolution SARslike TerraSAR-X
M. Schwerdt, D. Hounam and T. Molkenthin
IRS 2003, Dresden Germany1st October 2003
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Philosophy of Radar Calibration
PN-Gating Method
Concept of Antenna Pattern Model
DLR Calibration Facilities
Calibration / Validation Overview
Introduction
TerraSAR-X Features/Operation Modes
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Features/Operation Modes of TerraSAR-X
large number of:
calibrationmajor
challengecosts
affordable
single/dual polarisationwide range of swathpositions (20° - 55°)3 basic operation modes
Strip Map (26 look angles)ScanSAR (WS à 4 SS)Spotlight (123 look angles)
left/right looking SARexperimental modes
wide band widthalong track interferometry
activeantenna array
• operation modes
• antenna beams
26 elevation beams
123 elevation beams à100 azimuth patterns
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Calibration
RadiometricCharacteristics
Philosophy
Antenna PatternCompensation
RelativeAccuracy
imagemagnitude
calibration physicalunits
InternalCalibration
Stability
BiasCorrection
AbsoluteAccuracy
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New Calibration Concept
Internal Calibration PN-Gating Method In-Orbit Analysing ofIndividual TRMs
Antenna Pattern Precise Model Estimation of ActualAntenna Pattern
Measurementsas much as possible
Reliable ReferenceSufficient Numberof Ground Targets
(Index: PN = Pseudo Noise)
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Internal Calibration
3 Calibration Pulses:
– 1 Transmit Path1-2-4-5
– 2 Receive Path 6-4-2-1
– 3 Only RFE/DCE 6-5
controllingthe instrument
as a whole
individual modules?
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PN-Gating: technique of characterizing individual T/R modules while all modules are operating, i.e. a characterization under most realistic conditions.
Phase of each T/R moduleindividually shifted about ±π/2(phase shift keying) between Cal-pulses according to aPN code sequence.Each T/R module has a different PN code or codeshift.
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Superposition of all T/R Signals
s1 c1
s3 c3
sN cN
s2 c2
)t(c)t(s)t(S i
N
1i
ic
R/T
⋅=∑=
1 2 3 3 4 5bit t
correlationwith theinherent
Module code ci
extraction of individual
module signalsi^
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Standard Deviations versus Number of T/R ModulesS/N =20db, 30 Modules, Codelength=1023
For larger Number of T/R Modules code length wouldneed to be increasedcorrespondingly to achievethe same errors. But using of an ideally orthogonal code(Walsh sequence f.e.) thecross correlation of twodistinct sequences is 0. Thusthe code length can bereduced considerably down to 512 for 384 T/R modules.
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Amplitude & Phase Error as function of SNR (TerraSAR, 384 Modules)
Pseudo Noise Code Walsh Code
~ 0.2dB
~ 0.04°
Am
plitu
de/d
BPh
ase/
degr
ee
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Antenna Pattern Model
Estimation ofActual Antenna Pattern
Antenna PatternModel
Reference Patternfor Processing
Synthesis
Analysis
On-GroundMeasurements
Pre-FlightCharacterisation
In-FlightMeasurement
RainforestMeasurement
In-Orbit Verification Internal Calibration
PN-Gating
ModuleStepping
Module Failure
AntennaOptimisation
Synthesis
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Antenna Pattern ModelGoal: Derive all reference pattern required for SAR data processing; i.e.
provide an accurate estimation of the actual antenna pattern with a minimum number of costly in-flight antenna pattern measurements.
Pre-flight Characterization: calculating & analyzing antenna patterns of thedifferent operation modes as well as on-ground antenna pattern measurementslike those of a single radiation element or individual rows or panels.
In-Orbit Verification: in-flight antenna patterns measured in use of groundreceivers & by rainforest measurements (expensive!).
Internal Calibration: PN-gating method, an antenna pattern can be calculatedwith the actual excitation coefficients of the individual modules.
Module Failure Analysis: in case of contingencies, for example failed T/R modules, an optimization of the excitation coefficients of the remaining modules isintended in order to obtain the best beam of each operation mode.
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Antenna Pattern Model
Verification accuracy determines the minimum number of inflight measurements
When developing the modelcore attention
has to be focused on two questions:
What relevant beams have to be measured in order to verify sufficiently theantenna pattern model?
How can the best estimation of the actual pattern be extracted from all inputsand information described above?
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Essential TerraSAR-X calibration facilitiesStandard ground targets for bias correction
Ground receivers for in-flight measurements
Different analysis & evaluation tools, like- the presented antenna pattern model providing an estimation of the actualantenna pattern- SAR Product Control Software (SARCON) for target analysis of different calibration targets
Appropriated SAR processor, as there are two types of calibration data that haveto be processed:– SAR images covering deployed calibration targets,– Special calibration products like these of the presented
PN-gating method.
In addition to the high demands, keeping the cost affordable is a major challenge forcalibrating the TerraSAR-X instrument.
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Template
side lobe region main lobe region
Challenge of Antenna Pattern Optimisation
drifted or failedT/R modules
antenna array T/R modules Elevation Pattern and
side lobe region main lobe region
bestbeam steering
optimization ofremaining modules
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Bias Correction
On-Ground Calibration Targetswith known RCSExternal Calibration
Corner Reflector
Transponder
SRTM 2000ENVISAT/ASAR 2002
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Calibration Field for Scan SAR, ENVISAT/ASAR
Ascending
Passau
Basel
Descending
Strasbourg
Salzburg4
5
12
3
T T T TT T T T
T
wide swath405km
ENVISAT
asc
sub-swath65km - 108km
calibration field(CALIF)
Enclosed Area~ 405km
T: transponder
simplifiedelevationpattern
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ScanSAR Image of ASAR/ENVISAT, 12-10-02
D14
D01 D06
D02
D07D03
D05
D11D12
Munich
AlpsStrasbourg
• measured RCS• adjusted RCS
absolutecalibration constant
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Measured Azimuth Antenna Patterns of ASAR/ENVISAT
M . S c h w e rd t
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OverviewOverview
Overview