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
CEOS 2010, Zurich 26.08.2010Slide 3
CALIBRATION
RadiometricCalibration
Ant ModelVerification
AntPoint
GeoCal
Internal Cal
TDX Launch (21.06.2010)
RadiometricCalibration
-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
RadiometricCalibration
Geo Cal / Pattern
1. 2. 3. 4.
DRA-Campaigns4 cycles
Spring 2009TSX
TSX-1 / TDX-1 In-Orbit Calibration Plan
CEOS 2010, Zurich 26.08.2010Slide 4
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
CEOS 2010, Zurich 26.08.2010Slide 5
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]
CEOS 2010, Zurich 26.08.2010Slide 6
CALIBRATION
First results TDX-1: TRM Characterization – PN Gating
CEOS 2010, Zurich 26.08.2010Slide 7
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
CEOS 2010, Zurich 26.08.2010Slide 8
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
CEOS 2010, Zurich 26.08.2010Slide 9
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
CEOS 2010, Zurich 26.08.2010Slide 10
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
CEOS 2010, Zurich 26.08.2010Slide 11
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
CEOS 2010, Zurich 26.08.2010Slide 12
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
CEOS 2010, Zurich 26.08.2010Slide 13
CALIBRATION
Elevation Pointing by Notch Patterns over Rainforest
TDX Reference Pattern
MeasuredGamma Profiles
CEOS 2010, Zurich 26.08.2010Slide 14
CALIBRATION
HH-Elevation Pointing by Notch Patterns over Rainforest
TDX Reference Pattern
TSXProfiles
TDXProfiles
HH-Pointing Offset-11.0 mdeg
Measurement Accuracy 1.7 mdeg (1 )
CEOS 2010, Zurich 26.08.2010Slide 15
CALIBRATION
VV-Elevation Pointing by Notch Patterns over Rainforest
TDXProfiles
TDX Reference Pattern
TSXProfiles
VV-Pointing Offset-24.0 mdeg
MeasurementAccuracy
1.6 mdeg (1 )
Initial TSX-Offset-150 mdeg
CEOS 2010, Zurich 26.08.2010Slide 16
CALIBRATION
First Results TDX-1: Antenna Pattern by Ground Receivers
Ground Receiver
PositionVector
Transmit pattern only
Accuracy< ± 0.1dB
CEOS 2010, Zurich 26.08.2010Slide 17
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
CEOS 2010, Zurich 26.08.2010Slide 18
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
CEOS 2010, Zurich 26.08.2010Slide 19
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
CEOS 2010, Zurich 26.08.2010Slide 20
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