german aerospace center (dlr)microsoft powerpoint - pres_127_zink.ppt created date 12/10/2007...

Microwaves and Radar Institute – Hauke Fiedler – 29.11.2007

The TanDEM-X Mission: Overview and Status

H. Fiedler, M. Zink, G. Krieger, A. Moreira

German Aerospace Center (DLR)Microwaves and Radar InstituteOberpfaffenhofen

FRINGE 2007Microwaves and Radar Institute- Hauke Fiedler – 29.11.2007


2015201420132012201120102009200820072006200520042003

TanDEM-X Timeline

German Call for Proposals for a Future Earth Observation Mission

Phase A Study

Selection of TanDEM-X for Phase A Study

Final Decision

TerraSAR-X Operation

TanDEM-X Operation

Phase B/C/D

At least 3 years of joint operation


NGA (NIMA) Standards for Digital Elevation Models Spatial Resolution Absolute Vertical Accuracy

(90%) Relative Vertical Accuracy (point-to-point in 1° cell, 90%)

DTED-1 90 m x 90 m < 30 m < 20 m

DTED-2 30 m x 30 m < 18 m < 12 m

HRTI-3 12 m x 12 m < 10 m < 2 m

HRTI-4 6 m x 6 m < 5 m < 0.8 m

absolute height error single point errors

(90% confidence interval)

point-to-point errors(90% confidence interval)

hΔ

hΔ⋅2~

hΔ

relative height errorDefinition of 90% point-to-pointerrors: 1°

1°

hHRTIh σ⋅≈Δ 33.2%90


Available DEM Data Products

0

1

2

3

4

5

0 50 Coverage in Mio km²

Airborn

eLID

AR

Airborn

e SARPhotogram

metry

SRTM-C

(restr

icted

)

HR Satellit

es

Aster

SRTM-C

(free

)

SRTM-X

TanDEM-X

ERS 1/2

SPOT 5 HRS

DTE

D/H

RTI

Lev

elUSGS

GTOPO 30

global HRTI-3 DEM is a unique data product at a competitive price


Comparison TanDEM-X vs SRTM

TerraSAR-XStripmap DEM

SRTMDEM

Reso.: 8m x 8mBeff: 270 mhambig: 17.2 mAcc.: ~0.8 m

Reso.: 90m x 90mBeff: ~38 mhambig: ~175 mAcc.: ~16 m

Pictures Courtesy from IGARSS07: TerraSAR-X Interferometry: Report on a First Assessment (N. Adam et al.)Obs. Site: R. Metzig (HR)


both satellites transmit and receive independentlytemporal decorrelation & atmospheric disturbances

backup solution

Pursuit Monostatic

transmitter alternatesbetween PRF pulses

provides two baselinesenables synchronisation, calibration & verification

one satellite transmits and both satellites receive simultaneouslydual use of signal energy

requires synchronisation

Alternating BistaticBistatic

TanDEM-X Data Acquisition Modes


Impact of Oscillator Noise

increasedsidelobes

mainlobedispersion

azimuthdisplacement

interferometric phase errors

m

m

X

Txτ

Rxτ

independentoscillators

Tx

Rx

≠


Phase Referencing in TanDEM-X

phase referencing can achieveshort term rmse below 1°

Synchronisation LinkSynchronisation Link Analysis of Residual ErrorsAnalysis of Residual Errors


Tx Waveform Diversity for Synchronisation

Rx1f

Tx1

Rx2f

Tx2

*

gλ

2λ1λ

Rx1

Rx2

*

second bistatic second bistatic interferograminterferogram

*

firstfirst bistatic bistatic interferograminterferogram

*

monostatic monostatic interferograminterferogram

Rx1f

Tx1

Rx2f

Tx2

*

gλ

2λ1λ

Rx1

Rx2

*

second bistatic second bistatic interferograminterferogram

*

firstfirst bistatic bistatic interferograminterferogram

*

monostatic monostatic interferograminterferogram


Collision Avoidance

HELIX satellite formation enables safe operationhorizontal cross-track separation at equator by different ascending nodesvertical (radial) separation at poles by orbits with different eccentricity vectors

horizontalbaseline

verticalbaseline

NH(desc.)

SH(asc.)


linear phaseAntenna Tapering

12 m x 12 mPost Spacing

28-32 kmSwath Width

< 1 kmAlong-Track Disp..

500 mBaseline (perp.)

Ulaby (X-Band, VV, Soil)

Sigma Nought Model (90% occurence)

3 bit (BAQ)Quantization

1/10 pixelMis-Registration

2266 HzProcessed Bandwidth

~3500 HzPRF (swath variant)

4.8 m x 0.7 mAntenna Size (Tx, Rx)

4.1 dBLosses (rad., atm.,..)

4.3 dBNoise Figure TRM

18 %Duty Cycle

2260 WPeak Transmit Power

100 MHzChirp Bandwidth

0.031 mWavelength

Relative Height AccuracyValueParameter

DEM Performance Prediction (Bistatic Stripmap Mode)

90% 90% pointpoint--toto--pointpoint errorserrors

σ (standarddeviation)

BB⊥⊥ = 500 m= 500 m


linear phaseAntenna Tapering

12 m x 12 mPost Spacing

28-32 kmSwath Width

< 1 kmAlong-Track Disp..

1000 mBaseline (perp.)

Ulaby (X-Band, VV, Soil)

Sigma Nought Model (90% occurence)

3 bit (BAQ)Quantization

1/10 pixelMis-Registration

2266 HzProcessed Bandwidth

~3500 HzPRF (swath variant)

4.8 m x 0.7 mAntenna Size (Tx, Rx)

4.1 dBLosses (rad., atm.,..)

4.3 dBNoise Figure TRM

18 %Duty Cycle

2260 WPeak Transmit Power

100 MHzChirp Bandwidth

0.031 mWavelength

Relative Height AccuracyValueParameter

DEM Performance Prediction (Bistatic Stripmap Mode)

BB⊥⊥ = 1000 m= 1000 m


Height of AmbiguityTanDEM-X enables large baselines which allow for ultra high resolution DEMs with height accuracies in the sub-meter range, but …

πϕΔ 2=(height of ambiguity)

Compromise on Accuracy for Global DEMuse reduced baselinesadditional acquisitionsfor difficult terrain

acquisition scenariofor global DEM according to HRTI-3

Local/Regional Ultra High Resolution DEMs

multiple data acquisi-tions with large and small baselines

regional DEMs withsub-meter resolution(e.g. HRTI-4)


Data Acquisition Plan for Global DEM

•• map total Earth landmass with map total Earth landmass with two different baselinestwo different baselines

•• additional acquisitions in difficult additional acquisitions in difficult and mountainous terrain (~20 %)and mountainous terrain (~20 %)

BB11 BB22

m9 m45 m 30

011

1

213

2

1 ≈−

=⎭⎬⎫

≈≈

hhh

hh

0°

10°

20°

30°

40°

50°

60°

70°

1 32 54 76 8 9Beam Number

Latit

ude

HelixHelix aaΔΔee aaΔΔii ΨΨ

HH11 386 m386 m 330 m330 m 200200°°HH22 440 m440 m 385 m385 m 210210°°

HH33 440 m440 m 550 m550 m 210210°°

Optimized Set of HELIX Formations

Multiple DEM Acquisitions


Data Acquisition Scenario: Example

First Mission PhaseSecond Mission

PhaseThird Mission Phase

Different Mission Phases with its Helices (i.e. optimised height of ambiguity) will provide smooth performance over the Earth’s surface at all latitudes

Consequence: Final DEM will be available at end of mission


Combination of Interferometric DEM Acquisitions

hamb = 45 m

hamb = 30 m

optimum combination of all swaths


DEM Performance (flat terrain: rock & soil)


DEM Performance (20 % slopes)


DEM Performance (20 m vegetation)


Baseline Estimation and DEM Calibration• Both satellites are exposed to almost

identical orbit perturbations

- negligible azimuth modulation / twisting of DEM swath (ΔB < 0.25 mm for 500 km swath and ‘unmodelled’ δa < 100 nm/s2)

- vertical bias and tilt of raw DEM swaths due to initial baseline estimation errors

• Precise baseline estimation by

- double-difference GPS carrier-phase measurements

- accurate orbit propagation model

- several studies predict a 3-D accuracy in the order of 1-2 mm

baselinevector

jAρ

jBρ

kAρ

kBρ

j k

GPS satellites

DEMcalibration with:- swath overlaps- crossing orbits- ICESat- GPS Tracks- ...

BBestimatedestimated

BBtruetrue

""biasbias""

ΔΔBB

BBestimatedestimated

BBtruetrue

""biasbias""

ΔΔBB

similar orbit perturbations:

- drag, - Earth,- sun,- moon,- ...

relative orbit model


Secondary Mission Goals & New Techniques

S I R E V R a w D a ta

C h i r p S c a li n g

R a n g e F F T

R a n g e IF F T

R C M C o r r e c t i o n

R a n g eC o m p r e s s i o n

S e c o n d a r y R a n g eC o m p r e s s i o n

A z i m u t h F F TP h a s e C o r r e c t i o n

A z i m u t h S i d e -l o b e S u p r e s s i o n

A z i m u t h I F F T

A zi m u t h F F T

S I R E V I m a g e

L O S - C o r r e c t i o n a n d F i r s t O r d e r M o t i o n C o m p e n s a t i o n

A z i m u t h F F T

A zi m u t h I F F T

S e c o n d O r d e r M o t i o nC o m p e n s a t i o n

B0

CA

T s

τ

t

0f a

AC

Bτ

f a0

f r

C B A

I n t e g e rR e s a m p li n g



R a n g e F F T

R a n g e IF F T







A zi m u t h F F T

S I R E V I m a g e


A z i m u t h F F T



B0

CA

T s

τ

t

0f a

AC

Bτ

f a0

f r

C B A




R a n g e F F T

R a n g e IF F T







A zi m u t h F F T

S I R E V I m a g e


A z i m u t h F F T



B0

CA

T s

τ

t

0f a

AC

Bτ

f a0

f r

C B A


Pol-InSAR

Digital Beamforming

Bistatic Observations

Multi BaselineInSAR

Super Resolution

Along-Track Interferometry(fully polarimetric !)

(4 phase centres !)

(large bandwidth !) (bistatic angle !)

(HELIX formation !)

(flexible baselines !)


Along-Track Interferometry

Amplitude:Amplitude:

Interferometric Interferometric Phase:Phase:

r+Δr r

t+Δt t

Balong

accurate measurements of radial displacement betweentwo radar observations separated by a short time lag

(Ameland, Holland)

HELIX


ATI Performance: Measurement of Ocean Currents

vwind = 15 m/sτe = 4 ms

NRCS = -12.1 dB


NRCS = -15.6 dB


NRCS = -21.5 dBΔΔv v < 0.1 < 0.1 m/sm/s @ @ 50 m x 50 m50 m x 50 m


Along-Track Interferometry

Interferometric Interferometric Phase:Phase:

HELIX

sensitive to fast movements

sensitive to slow movements

split antenna

0.2 km/h~9 km/hΔv

12 km/h500 km/hvamb

45°θinc

- 12 dBm2/m2σ0

12 m12 mΔx

100 m2.4 mBalong


Digital Beamforming with Four Phase Centres

without reconstruction with reconstruction

Ch. 2Ch. 1

SAR Proc.

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

EnablesHigh

ResolutionWide Swath

Imaging

Ch. 3 Ch. 4

AmbiguitySuppression


“Double Differential SAR Interferometry”

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

h(t1)

Δh ~ ϕ2 - ϕ1

coherence between passes not mandatory

ϕ1pass 1

pass 2

Δh < 10 cm h(t2)

ϕ2

Bistatic Strip mapB = 3000 m Δx = 12 m

Bistatic Strip mapB = 3000 m Δx = 12 m

e.g. difference between two single-pass cross-track interferograms


Polarimetric SAR Interferometry

polarisations

pdf(μmin)

pdf(μmax)

Parametersh = 1.2 mβ = 4.0 dB/mμmin = -7.0 dBμmax = 3.0 dBB⊥ = 4 kmθinc = 35°Δx = 30 m

Parametersh = 1.2 mβ = 4.0 dB/mμmin = -7.0 dBμmax = 3.0 dBB⊥ = 4 kmθinc = 35°Δx = 30 m


RxθTxθ

φ

Extended Observation Space

Bistatic Radar Imaging

Color Color compositecomposite of of threethree bistatic SAR bistatic SAR imagesimagesfromfrom DLRDLR--ONERA bistatic SAR ONERA bistatic SAR experimentexperiment

(P. (P. DuboisDubois Fernandez et al. , IEE Fernandez et al. , IEE ProcProc. RSN, 2006). RSN, 2006)improved detection, segmentation, and classification from bistatic RCSnew image and object parameters (bistatic Doppler, multiple shadows, ...)


TanDEM-X Summary

TanDEM-X is the next German Earth Observation Mission to be launched in 2009

TanDEM-X has outstanding scientific and commercial potentials

TanDEM-X key technologies are:

bistatic radar operation and phase synchronisation

precise baseline determination

close formation flying capability

new algorithms for interferometric processing

TanDEM-X plays a key role in the development of next generation bistatic and multistatic SAR missions and applications

german aerospace center (dlr)microsoft powerpoint - pres_127_zink.ppt created date 12/10/2007...

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