Polarisation Capabilities and Status of TerraSAR-Xearth.esa.int/.../441/pres_9_hajnsek_441.pdf ·...
Transcript of Polarisation Capabilities and Status of TerraSAR-Xearth.esa.int/.../441/pres_9_hajnsek_441.pdf ·...
[email protected] 26-Jan-2009
Polarisation Capabilities and Status of TerraSAR-X
Irena Hajnsek, Josef Mittermayer, Stefan Buckreuss, Kostas Papathanassiou German Aerospace CenterMicrowaves and Radar Institute
Slide 2
TerraSAR-X Satellite
Solar Generator
X-Band Radar Antenna384 Transmit/Receive Modules
X-Band Downlink AntennaData Rate: 300 MBit/sec
256 Gbit Solid State Mass Memory
S-Band TM/TC Antenna
Thrusters
Wet mass: 1209 kgOrbit average power: 800 W Size: 5 m height × 2.4 m diameter
Slide 3
TerraSAR-X Satellite Key FeaturesHigh resolution in SpotLight mode
Possibility of large area coverage by utilizing ScanSAR mode
Multi-polarization capability
Left Looking Mode (roll maneuver of S/C)
Dual Receive Antenna (DRA) Mode (ATI, MTI, Quad. Pol.)
300 MHz transmit bandwidth (1 m range resolution)
Reference orbit with ±250 m orbit tube (repeated acquisitions, interferometry, etc.)
Total Zero Doppler Steering
Secure operation by encryption of commands and data downlink
Prepared for TanDEM-X operation (synchronization)
Slide 4
Munich Oktoberfest Site
• Januar – Juni 2008 • 31.7. – 22.8.2008 • DifferenzInstitut für Methodik
der Fernerkundung
Slide 5
Data Quality
AchievementsImprovementsTrendsPlans…
Slide 6
Calibration: Results of the Commissioning PhaseGoal: SAR product verification and release of the basic products
• Verification of format, annotation and content passed
• Updated basic product specificationImprovements w.r.t. initial version as for example (Stripmap)
o absolute radiometric accuracy: 1.1 dB 0.6 dB
o relative radiometric accuracy 0.68 dB 0.31 dB
o spotlight mode (azimuth) resolution 2.2 m 1.7 m
o pixel localization accuracy 2.0 m 0.3 m in range2.0 m 0.53 m in azimuth
o side lobe ratio improved by approx. 10 dB**(at the cost of a reduction of the slant range resolution of 9 % from 1.1 m to 1.2 m)
Slide 7
DubaiStripmapVV-pol.
• 26. Juni 2007 • 7. April 2008• Difference
Slide 8
High Resolution Spotlight Image of Anak KrakatauImproperly amplified DC-part of SAR image
=> range stripes
Slide 9
High Resolution Spotlight Image of Anak KrakatauSpectral thresholding eliminates range stripes (improved replica implementation)
Slide 10
Noise Correction in TerraSAR-X Processor TMSP
noise pattern in low backscatterareas typical for ScanSAR
results from azimuth and elevation antenna pattern correction for the individual bursts
signal is perfectly calibrated but additional noise power is inhomogeneously distributed
multiple superposition of statistical signal and noise distributions
impairs some applications (e.g. ship detection)
ScanSAR Sydney, Australia (2008-01-30)
Slide 11
noise corrected product
New SAR processor softwareis activated since Dec 1st, 2008
Noise Correction in TerraSAR-X Processor TMSP
Slide 12
Instrument Stability:• I/Q Statistic stable, no Trend• TRM Monitoring (rel. ampl/phase): < 0.23 dB / < 2.0 deg (1σ)
Antenna Pattern Monitoring• Shape within Main Beam• Gain-Offset between different beams
Radiometric Stability• Requirement over 6 months 0.5 dB (1σ) (requirement)
• Observed over 1 year0.14 dB
Calibration: Resumé after 1 Year of Operations
≤ ±0.2 dB (peak to peak)
No significant variation has been observed since launch!
Slide 13
Experimental Modesof TerraSAR-X
Slide 14
TOPSAR Acquisition ModeTOPSAR is a modified ScanSARmode:
Ambiguity Reduction„Scalloping“ Reduction
TOPSAR Interferogram
Slide 15
range
azim
uth
Conducted on 5th of November 2007TX with TerraSAR-X, RX with F-SARImportant preparation for TanDEM-X
Clock synchronizationIn-orbit-phase-noise investigationsPerformance verification of bistaticprocessing and imaging techniques
Bistatic Imaging
Slide 16
Principle
• For transmit the full antenna is used
• For receive the antenna is ‚electrically‘ divided into two sections inazimuth direction two independent receive channels are available
New Experimental Modes
• Along-Track Interferometry (ATI)(Moving Target Indication, Widespread Traffic Control, Ocean Current Measurement)
• Quad polarization(Sea/Ice, Snow Cover, Urban Environment)
Transmit Receive
Dual Receive Antenna Mode (DRA Mode)
TX: V H V H …RX1: V V V V …RX2: H H H H …CH1: VV HV VV HV …CH2: VH HH VH HH …
Quadpol switching scheme
Slide 17
Polarization ModesH H H H
H H H H
Transmit
Receive
Single Polarization• 1 polarization
channel, {HH, VV}• stripmap, spotlight,
ScanSARDual Polarization• 2 polarization
channels, {HH/VV, HH/HV, VV/VH}
• stripmap, spotlight• coherent pol. phase• smaller elevation beam
H H H HTransmit
ReceiveV
H H H H
V V VH H H H
Quad Polarization• All 4 pol. channels• Stripmap• coherent pol. Phase• smaller elevation beam• Experimental product
H H H HTransmit
ReceiveV
V V V V
V V V
H H H HH H H H
V V V V
Twin Polarization• 2 polarization
channels, {HH/VV, HH/HV, VV/HV}
• stripmap• incoherent pol. phase• full elevation beam
H HTransmit
ReceiveV
H
V VHH
Slide 18
First TerraSAR-X Quadpol Image!
Workuta, Russia StripmapJune 23, 2008red: HH-VVgreen: (HV+VH)/2
blue: HH+VV
Slide 19
Polarimetric Analysis (dual pol HHVV) @ X-Band
HHVV Coherence(amplitude)
RGB (hh+vv,hh,hh-vv)
Slide 20
Polarimetric Analysis (dual pol HHVV)
HHVV Coherence(phase)
RGB (hh+vv,hh,hh-vv)
Slide 21
Polarimetric Analysis (dual pol HHVV vs quad pol)RGB
(hh+vv,hh,hh-vv)
RGB (hh+vv,2hv,hh-vv)
Slide 22
Dual Receive Mode Implementation (1)
Decision to activate the redundant receive channel in March‘08
Commanding of DRA mode was proved
Instrument is capable to execute the DRA mode
SAR Workflow is running well
Manually(!) tuned quadpol product is available (June’08, IGARSS’08)
Identified problems:
Channel decoupling is problematic, on-ground characterization not sufficient
New command structure w.r.t. additional cal pulses to be developed
Commanding and processing to be iteratively optimized
Slide 23
Dual Receive Mode Implementation (2)
Work in progress:
Presently test data takes are carried out and evaluated
Review of results and final decision on way forward
Calibration campaign (3 cycles) in spring 2009 (tbc)
Final product release in summer 2009 (tbc)
Quota limitation for future acquisitions to be discussed
(Reliability calculation due to the use of redundancies)
Slide 24
Spacecraft and ground segment are fully operational
Image products (Spotlight, Stripmap, ScanSAR) are calibrated and released
Product quality within initial specification or better!
SAR instrument proved to be very stable
Demonstration of Repeat Pass Interferometry, Along Track Interferometry, persistent scatterer evaluation, TOPSAR, total zero Doppler steering
Demonstration of quadpol mode
The use of TerraSAR-X data was demonstrated for geo-scientific applications, oceanography and disaster monitoring during commissioning phase
Preparation of TanDEM-X mission gains priority…!
Status Summary