Microwaves and Radar Institute [email protected] Distributed Imaging with TSX and TDX Pau Prats, Paco López-Dekker, Francesco De Zan, Steffen Wollstadt,

Microwaves and Radar Institute [email protected]

Distributed Imaging with TSX and TDXDistributed Imaging with TSX and TDX

Pau Prats, Paco López-Dekker, Francesco De Zan, Steffen Wollstadt, Markus Bachmann, Ulrich Steinbrecher, Rolf Scheiber, Andreas Reigber, Gerhard Krieger

Microwaves and Radar Institute (HR)German Aerospace Center

Microwaves and Radar Institute > Februar 2010 July 29th, 2011Slide 2Microwaves and Radar Institute

Motivation

Future SAR missions will exploit bi- and multistatic SAR systems.

Such systems increase the potential, reliability and flexibility of future SAR missions.

Potential: frequent monitoring, wide-swath imaging, single-pass interferometry, enhanced products (e.g. in terms of resolution).

Perform new experiments! ;c)

G. Krieger and A. Moreira, “Spaceborne bi- and multistatic SAR: potential and challenges”, IEE Proc.-Radar Sonar Navig., vol. 153, no. 3, June 2006.


VU 3 > Alberto Moreira

• SAR Interferometer• Close formation• Global DEM (HRTI-3)

TerraSAR-X add on for Digital Elevation Measurements



Bistatic SAR ImagingBistatic SAR ImagingBistatic SAR ImagingBistatic SAR Imaging

Super ResolutionSuper ResolutionSuper ResolutionSuper Resolution

Polarimetric SAR InterferometryPolarimetric SAR InterferometryPolarimetric SAR InterferometryPolarimetric SAR Interferometry

Ground Moving Target IndicationGround Moving Target IndicationGround Moving Target IndicationGround Moving Target Indication

SAR TomographySAR TomographySAR TomographySAR Tomography

SeaSea ice monitoring ice monitoringSeaSea ice monitoring ice monitoring

RxTx

Double Differential InterferometryDouble Differential InterferometryDouble Differential InterferometryDouble Differential Interferometry

h(t1)

h ~ 2 - 1

coherence between passes not mandatory

1

pass 1

pass 2

h < 10 cmh(t2)

2

Bistatic Strip mapB = 3000 m x = 12 m

Bistatic Strip mapB = 3000 m x = 12 m

Digital BeamformingDigital BeamformingDigital BeamformingDigital Beamforming

without reconstruction with reconstruction

Ch. 2Ch. 1

SAR Proc.

P2(f)P2(f) P3(f)P3(f)P1(f)P1(f) P4(f)P4(f)

EnablesHigh

ResolutionWide Swath

Imaging

Ch. 3 Ch. 4

AmbiguitySuppression

Rx1 Rx2

B1

B2

B3

TanDEM-X: Secondary Mission Objectives

Crossed-orbitsCrossed-orbitsCrossed-orbitsCrossed-orbits


Some Experiments with Distributed Imaging

Demonstration of distributed imaging with the following experiments:

Range-resolution enhancement

Azimuth-resolution enhancement

Quad-pol synthesis with dual-pol acquisitions

Digital beamforming

Elaborated manual commanding of each experiment

Experiments performed during the monostatic commissioning phase:

20 km ~ 3 s

TSXTDX

Baseline needs to be

compensated


TanDEM-X Commissioning Phase

June‘10 July‘10 Aug‘10 Sep‘10 Oct‘10 Nov‘10 Dec‘10

EarlyOrbitPhase

Grg SegmentCheckout

Bi-static Commissioning Phase

20 km FormationTDX Orbit Drift16.000 km 20 km Close Helix-Formation 300-400 mLaunch

21 June

DEM Acquisition

First SAR Image 24 June (MET +3.6)

First DEM 16 July (MET +25)

TDX Monostatic Comm. Phase

6 Months Commissioning Phase

First close formation DEM 19 October (MET +124)

First bi-static SAR image 8 August (MET +48)

First single-pass bi-static DEM 2 October (MET +107)


Super Resolution in Range: Step-Frequency with TSX and TDX

f0 - f

f0 + f

f0

fr

fr

fr

TSX

TDX

Limitation: RF filter allows maximum band of 300 MHz

Advantages within limitation:

Increased SNR

Data rate distributed among satellites

Baseline compensation for proper coherent combination

Negligible spectral shift for current configurations (but nevertheless considered)

300 MHz


Super Resolution in Range: Step-Frequency with TSX and TDX

4ˆ , ,cal r x r r x

,r r xInterferometric chain

(TAXI)Common range-band

filter

ECS + BAS (TAXI)Shift after range compression due to

non-centered chirp spectrum

TSXraw data

TDXraw data

TSX SLC TDX SLC

Calibration phase

Phase and gain calibrationCoherent addition

Weighting

Range-resolution- enhanced SLC

Coregistered TDX SLC

(non-filtered)

Coregistration

Common-band spectruminterferogram


Super Resolution in Range: Experimental Setup

Data takes over Sydney, Australia, on August 15 and 26, 2010


Super Resolution in Range: Experimental Results

azim

uth

range


Super Resolution in Range: Experimental Results (II)

azim

uth

range

Common-band interferogram


Super Resolution in Range: Experimental Results (III)

azim

uth

range


Super Resolution in Range: Experimental Results (IV)

azim

uth

range


Super Resolution in Range: Experimental Results (V)

azim

uth

range


Super Resolution in Range: Experimental Results (VI)

azim

uth

range

Interferometric coherence between synthesized images

Interferometric phase between synthesized images


Super Resolution in Azimuth

fDC,1

fDC,2

fDC,mean

fa

fa

fa

TSX

TDXInterferometric chain

(TAXI)Common azimuth-band

filter

ECS (TAXI)

TSXraw data

TDXraw data

TSX SLC TDX SLC

Calibration phase

Phase and gain calibrationCoherent addition

Weighting

Azimuth-resolution- enhanced SLC

Coregistered TDX SLC

(non-filtered)


Super Resolution in Azimuth: Experimental Setup

Data take over Neustrelitz, Germany, on September 20, 2010


Super Resolution in Azimuth: DTAR AnalysisTDXDTAR: -21.67 dB

TSXDTAR: -21.04 dB

Maximum bandwidthDTAR: -19.91 dB

Twice the resolutionDTAR: -21.42 dB


Super Resolution in Azimuth: Experimental Results (I)

azimuth

range


Super Resolution in Azimuth: Experimental Results (II)

azimuth

range

Common-band interferogram


Super Resolution in Azimuth: Experimental Results (III)

azim

uth

range


Super Resolution in Azimuth: Experimental Results (IV)

azim

uth

range


Super Resolution in Azimuth: Experimental Results (V)

azim

uth

range


Super Resolution in Azimuth: Experimental Results (VI)

Measured resolutions over a corner reflector:

TSX: 2.97m

TDX: 2.97 m

Combined: 1.49 m


Quad-Pol Synthesis with Dual-Pol Acquisitions

Each satellite acquires a co-pol and a cross-pol channel, e.g. HH-VH and HV-VV

The cross-pol channel is used to estimate the calibration phase

Better SNR and DTAR when compared to the experimental quad-pol product using the dual receive antenna (DRA) mode

DLR’s E-SAR example: quad-pol synthesis at C-band with repeat-pass dual-pol acquisitions [1]

E-SAR

[1] R. Scheiber et al., “Radar data processing, quality analysis and level-1b product generation for AGRISAR and EAGLE campaigns,” in AGRISAR and EAGLE Campaigns Final Workshop, Noordwijk, The Netherlands, Oct. 15-16 2007.


Quad-Pol Synthesis: Experimental Results

New acquisitions performed in bistatic mode are on their way.

azimuth

range


Conclusion & Future Work

Proof of concept of several experiments with TSX and TDX

Range-resolution enhancement

Azimuth-resolution enhancement

Quad-pol synthesis with dual-pol acquisitions

Qual-pol synthesis with dual-pol acquisitions using bistatic data (close formation)

Further performance analyses, especially for the azimuth case

By doubling the PRF one can obtain simultaneously a resolution improvement in both dimensions

Digital beamforming with an interferometric baseline



Thank you for your attention!

Documents

Microwaves and Radar Institute [email protected] Distributed Imaging with TSX and TDX Pau Prats, Paco López-Dekker, Francesco De Zan, Steffen Wollstadt,