First Calibration Results of the TanDEM-X...

CEOS 2010, Zurich, 26th August

CALIBRATION

First Calibration Results of the TanDEM-X Satellite

Marco Schwerdt , Jaime Hueso Gonzalez,Markus Bachmann, Björn Döring, Dirk

Schrank, Benjamin Bräutigam

CEOS 2010, Zurich 26.08.2010Slide 2

CALIBRATION

Outline

Calibration ScheduleInternal CalibrationGeometrical CalibrationAntenna PointingAntenna Model VerificationAbsolute Calibration


CALIBRATION

RadiometricCalibration

Ant ModelVerification

AntPoint

GeoCal

Internal Cal

TDX Launch (21.06.2010)


-2. -1. 0. 1. 2. 3. 5. 7.6.4.Repeat Cycle

LEOP

8. 9. 10. 11. 12.

Close formation

1 monthDay 90

Error ModelVerification

TDX Commissioning Phase

Ref

Baseline Bias Determination

Sync Link Verification

6 cycles 4-5 cycles

Mosaicing and Cal Test

DEM

Acq

uisi

tion

20 km formationpursuit mono-static mode

Mai

nten

ance InterferometricCP

Man

euve

rs

FQR

Radiomet.Verification

Ant ModelVerification

GeoCal

1. 2. 3. 4.

TSX Re-Calibration4 cycles

AntPoint

Summer 2009


Geo Cal / Pattern

1. 2. 3. 4.

DRA-Campaigns4 cycles

Spring 2009TSX

TSX-1 / TDX-1 In-Orbit Calibration Plan


CALIBRATION

First Results: Chirp Comparison of TDX-1 – TSX-1

imagefrequencies

chirp

TSX-1TDX-1

Receive pulses, BW = 150MHz, UP-Chirp, Pulse Length = 32µs

important forBistatic Operation


CALIBRATION

First results TDX-1: TRM Characterization – PN Gating

blue: measured in flight coldred: measured in flight hotblack: on ground characterization

Receive

Phas

e [d

egre

es]

Am

plit

ud

e [d

B]

Transmit

Phas

e [d

egre

es]

Am

plit

ud

e [d

B]


CALIBRATION

First results TDX-1: TRM Characterization – PN Gating


CALIBRATION

2.5 MONTHS (Summer 2010)1. Geometric Calibration2. Antenna Pointing3. Antenna Model4. Radiometric Calibration

StripMap and ScanSAR

DLR Cal Test Sites• South Germany

30 Point Targets, 17 permanentlyinstalled Corner Reflectors

• Amazon Rainforest

TanDEM-X Calibration Team32 DLR colleagues

• 60 Calibration Campaignswith Reference Targets(Transponders and Corners)

• Analysis and Evaluation of> 1000 Datatakes

TDX-1 Monostatic Calibration Campaign


CALIBRATION

D01x

D02x D03 x

D04x

D05x

D06x

D07x

D24-D30

x xx

xx

xx

D08

x D09x D10

xD12

xD14

x

D17x

D18x

D19x

D20x

D22 x

D11x

D13x D15

x

D16x

D21x D23

x

40km

120km

S007S007

Complete Calibration Field in South Germany near by OP

Munich


CALIBRATION

- Azimuth Shift

- Instrument Delay- Tropospheric Effects

Time Annotation of Source Packets

Range Delay

Connection between SAR Dataand Geographic Position on Earth Surface

is calibrated

Geometric Calibration

6 Corner Reflectorsper Pass

8 Beams


CALIBRATION

TDX Azimuth Shift

-0,4

-0,3

-0,2

-0,1

0

0,1

0,2

0,3

0,4

15 20 25 30 35 40 45 50 55Look Angle [deg]

Azi

mut

h S

hift

[mse

c]

AscDesOffset

TDX Azimuth ShiftA

zimuth Shift [m

]

2,84

2,13

1,42

0,71

0,0

-0,71

-2,13

-2,84

-1,42

Pixel Accuracy in Azimuth: = 70 μsec / 49.9 cm

= -176 sec / -1.251m = 76 μsec / 54.0 cm

TSX-1 (2007)Offset: = -38.6 μsec / -27.4 cm


CALIBRATION

TDX Geometric Calibration

-1,5

-1,25

-1

-0,75

-0,5

-0,25

0

0,25

0,5

0,75

1

1,25

1,5

15 20 25 30 35 40 45 50 55Look Angle [deg]

Del

ta R

ange

[m]

AscDesOffset

Pixel Location Accuracy Azimuth = 2.03 nsec / 30.4 cm

Offset = 0.22 nsec / 3.29 cm

TDX Range OffsetD

elta Instrument D

elay [nsec]

10,01

6,68

5,00

1,67

0,00

-1,67

-8,34

-10,01

-5,00

= - 3.14 nsec / -47.0 cm = 2.07 nsec / 31.0 cm

TSX-1 (2007)

3,34

8,34

-3,34

-6,68

Annotated Instrument Delay 208.09 [nsec]

s026

s023

s019

s016s009s005

s003

s012


CALIBRATION

• ScanSAR-Mode: Several Beams measured during one Pass

• across an Area of 750 x 750 km²

120 km range

60 k

m a

zim

uth

PurposeDetect changes in the antenna front end and wave guides

First Antenna Pattern Measurements of TDX-1

strip_003 strip_004 strip_005 strip_006

Quality Parameters

*

max

µ

min


CALIBRATION

Elevation Pointing by Notch Patterns over Rainforest

TDX Reference Pattern

MeasuredGamma Profiles


CALIBRATION

HH-Elevation Pointing by Notch Patterns over Rainforest


TSXProfiles

TDXProfiles

HH-Pointing Offset-11.0 mdeg

Measurement Accuracy 1.7 mdeg (1 )


CALIBRATION

VV-Elevation Pointing by Notch Patterns over Rainforest

TDXProfiles


TSXProfiles

VV-Pointing Offset-24.0 mdeg

MeasurementAccuracy

1.6 mdeg (1 )

Initial TSX-Offset-150 mdeg


CALIBRATION

First Results TDX-1: Antenna Pattern by Ground Receivers

Ground Receiver

PositionVector

Transmit pattern only

Accuracy< ± 0.1dB


CALIBRATION

First Sequential Ground Receiver Acquisition

3s azimuth separation ≈ 20 km

Direct measurement of the satellite separation in along track Pursuit monostatic phase

1st absolute comparative measurement of transmitted power < 0.5dB difference in the transmit power

RX


CALIBRATION

• Radiometric Stability

Abs. Cal Factor2007 - 56.58 dB

2009 - 56.43 dB

μ ≤ ± 0.2dBwithin Scene

Radiometric Calibration TSX-1

TerraSAR-Xis extremely stable

0.15dBover 2 years

μ ≤ ± 0.2dBwithin full

performancerange

Requirement 0.5 dB (1)over 6 months !

≤ ± 0.2dB

• Antenna Model

6 Corner Reflectorsacross the swath

3 Beams (low, mid, high, Inc)strip_007

-57,6

-57,4

-57,2

-57

-56,8

-56,6

-56,4

-56,2

-56

-55,8

-55,6

Abs

Cal

Fac

tor[

dB]

near mid far

-57,6

-57,4

-57,2

-57

-56,8

-56,6

-56,4

-56,2

-56

-55,8

-55,6

10 15 20 25 30 35 40 45

Look Angle [deg]

Abs

Cal

Fac

tor[

dB]

strip_002strip_007strip_013


CALIBRATION

-57,6

-57,4

-57,2

-57

-56,8

-56,6

-56,4

-56,2

-56

-55,8

-55,6

-55,4

-55,2

Target

Abs

Cal

Fac

tor [

dB]

20100813 TDX

20100815 TDX

20100816 TDX

Corner Transponder-57,6

-57,4

-57,2

-57

-56,8

-56,6

-56,4

-56,2

-56

-55,8

-55,6

-55,4

-55,2

Target

Abs

Cal

Fac

tor [

dB]

20100813 TDX

20100815 TDX

20100815 TSX

20100816 TDX

20100816 TSX

Corner Transponder

• Cross Calibration Error TSX TDX cross ~ 0.02dB• TSX still extreme stable AbsCalFac= 0.04dB (2009/2010)• AbsCalFactor TDS – TSX TDX-TSX ~ 0.88dB

First Results of Absolute Radiometric Calibration

X

X

X

X

μ (TDX, CR)- 55.69 dB

μ (TDX, TX)- 56.19 dB

μ (TSX, CR)- 56.57 dB

μ (TSX, TX)- 57.05 dB

= - 0.50 dB

= - 0.48 dB

= + 0.88 dB

First Results based on 3 Acquisitions are very promising

μ2009 (TSX, CR)- 56.53 dB


CALIBRATION

Conclusion

Results quite similar to calibration results of TSX

Internal Calibration: No TRM failure up to now

Geometric Calibration: Corrected azimuth and range shifts

Antenna Pointing: Mis-alignment corrected

Antenna Model Verification and Absolute Calibration:

Promising first results

Campaigns:

30 calibration measurement campaigns completed

About 30 more coming during the next month

First Calibration Results of the TanDEM-X...

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