IGARSS 2010, Honolulu, 29th July
CALIBRATION
Monostatic Calibration of both TanDEM-X Satellites
Marco Schwerdt , Jaime Hueso Gonzalez,Markus Bachmann, Dirk Schrank,
Clemens Schulz, Björn Döring
IGARSS 2010, Honolulu 29.07.2010
Slide 2
CALIBRATION
AntPoint
GeoCal
GS/SCCheckout
TSX-1 Launch
(15.06.2007)
Radiometric
Calibration
Ant ModelVerification
TSX-1Commissioning Phase
5 Months
Summer 2007
TDX-1Comm. Phase
TDX-1 Launch
(21.06.2010)
5 Months
(Mono + Bi: 3+2)GeoCal
AntPoint
• • •
• •
•
ChannelImbalance
DRACampaign
s1 Month
Spring 2009
RadiometricCalibration
Antenna Model
Cross Talk
RadiometricCalibration
Ant ModelVerification
GeoCal
TSX-1Re-
Calibration1 Month
AntPoint
Summer 2009
≈
Op
era
tio
na
l P
ha
se
≈
TSX-1 / TDX-1 In-Orbit Calibration Plan
IGARSS 2010, Honolulu 29.07.2010
Slide 3
CALIBRATION
TSX-1 Calibration
IGARSS 2010, Honolulu 29.07.2010
Slide 4
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 TSX-1
Internal Delay: 208.09 ns
-3-2,5
-2-1,5
-1-0,5
00,5
11,5
22,5
3
15 20 25 30 35 40 45 50 55
Look Angle [deg]
Del
ta R
ang
e [m
]
Tests 2007 Mean 2007
Tests 2009 Mean 2009
2m (requirement)
30 cm (1)(2 ns)
• Pixel localizationaccuracy (range)
6 corner reflectorsper pass
8 beams
No trendsince 2 years 3.75 cm
(0.25 ns)• Residual offset
(in-flight OGC)
Near range Far range
IGARSS 2010, Honolulu 29.07.2010
Slide 5
CALIBRATION
Updates Improved ground
receiver position Re-adjustment between
star trackers
Pointing Determination in Azimuth TSX-1Antenna pointing determination
-30.00
-20.00
-10.00
0.00
10.00
20.00
30.00
17 22 27 32 37 42 47 52
Elevation look angle in deg
Do
pp
ler
in H
z
Pointing Calibration (2007)
Pointing Recalibration (2009)
Improvements 2007 2009 Measurement accuracy ≤ 7.9 Hz ≤ 2.6 Hz (1) per
pass < 1.0 mdeg < 0.33 mdeg
Mean doppler 16 Hz 5.9 Hz Residual pointing error 2 mdeg 0.74 mdeg
Notch patternswith different look angles
4 ground receivers per pass
Near range Elevation look angle [degree] Far range
Fre
qu
en
cy s
hift
du
e t
o m
isp
oin
ting
[H
z]
IGARSS 2010, Honolulu 29.07.2010
Slide 6
CALIBRATION
PurposeDetect changes in the antenna front end and waveguides
120 km range
60 k
m a
zim
uth
Antenna Pattern Monitoring TSX-1
strip_003 strip_004 strip_005 strip_006
Quality parameters
*
max
µ
min
ScanSAR-mode: several beams measured during one pass
Across an areaof 750 x 750 km²
strip_003 strip_004 strip_005 strip_006
IGARSS 2010, Honolulu 29.07.2010
Slide 7
CALIBRATION
Antenna Pattern Long Term Monitoring TSX-1
Shape deviationwithin
the main beam
Beam-to-beamgain prediction
stable, no trendRequirement still fulfilled
Δ < ± 0.2dB
IGARSS 2010, Honolulu 29.07.2010
Slide 8
CALIBRATION
-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]
Ab
s C
al F
acto
r [d
B]
strip_002
strip_007
strip_013
= -56.50 dB = 0.21 dB
= -56.76 dB = 0.24 dB
= -56.45 dB = 0.16 dB
strip_007
-57,6
-57,4
-57,2
-57
-56,8
-56,6
-56,4
-56,2
-56
-55,8
-55,6
Ab
s C
al F
ac
tor
[dB
]
near mid far
= -56.73 dB = 0.22 dB
= -56.65 dB = 0.17 dB
= -56.62 dB = 0.18 dB
= -56.67 dB = 0.18 dB
• Radiometric Stability
Abs. Cal Factor2007 - 56.58 dB
2009 - 56.43 dB
µ2009 = -56.53dB + 0.10dB (CR) = -56.43dB
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
CR: corner reflector
6 corner reflectorsacross the swath
3 beams (low, mid, high inc.)
IGARSS 2010, Honolulu 29.07.2010
Slide 9
CALIBRATION
Calibration Tasks Performed in 2009 TSX-1
TerraSAR-X in Dual Receive Antenna (DRA) Mode
2 instrument chains on receive (main and redundant)
2 antenna halves
Quad-pol mode
Along track interferometry
DRA Campaigns Geometric calibration Antenna model verification Channel imbalance, phase Channel imbalance, amplitude radiometric calibration Cross talk
Ch. 2
Ch. 1
IGARSS 2010, Honolulu 29.07.2010
Slide 10
CALIBRATION
Channel Imbalance: Amplitude TSX-1
-0.18dB antenna gain
Correction, V-pol on receive
max. offset0.44dB
Channelimbalance
0.26 dB
Abs. rad. accuracy during DRA campaigns
0.30 dB (1)
QuadPol Corner
-57,6
-57,4
-57,2
-57
-56,8
-56,6
-56,4
-56,2
-56
-55,8
-55,6
Polarisation
Ab
sC
al
Fa
cto
r [d
B]
measured data
mean
HH VV
= -56.46 dB = 0.09 dB
= -56.65 dB = 0.12 dB
QuadPol Transponder
-57,6
-57,4
-57,2
-57
-56,8
-56,6
-56,4
-56,2
-56
-55,8
-55,6
Polarisation
Ab
sCal
Fac
tor
[dB
]
= -56.25 dB = 0.29 dB
= -56.49 dB = 0.33 dB
= -56.05 dB = 0.19 dB
= -56.40 dB = 0.39 dB
HH HV VH VV
(45° constellation)
IGARSS 2010, Honolulu 29.07.2010
Slide 11
CALIBRATION
Receiver for
V-pol
Strip_013, des, Inc. 43.7° (16-04-2007)
One-Way Cross Polar Isolation TSX-1
Ground receivers aligned for V-pol
1-way azimuth pattern measured per pass
H
V
Cross talk
Requirement ≥ 24dB (1-way, StripMap)
1-way cross polar isolation (on transmit)
> 34dB
IGARSS 2010, Honolulu 29.07.2010
Slide 12
CALIBRATION
TerraSAR-X Calibration Tasks Performed in 2009TerraSAR-X Calibration Team
27 DLR colleagues
DRA modecalibration
Radiometric stability0.15 dB (over 2 years)
Absolute radiometric accuracy
0.39 dB (StripMap)0.46 dB (DRA Quad-pol)
Channel imbalance0.26 dB / < 3 deg
Cross talk
< - 24.9 dB
213 acquisitions171 over rainforest
42 cal-field (306 targets)
Re-calibration2 years after launch
CALIBRATION
TerraSAR-X is stable with outstanding
performance
Pointing accuracy< 1 mdeg (azimuth)< 4 mdeg
(elevation)
Pixel localization accuracy
31 cm (range)54 cm (azimuth)
Slide 12
IGARSS 2010, Honolulu 29.07.2010
Slide 13
CALIBRATION
TDX-1 Calibration
IGARSS 2010, Honolulu 29.07.2010
Slide 14
CALIBRATION
TerraSAR-X calibration performance sets a solid basis
TDX-1 Calibration Goals
SAR Quality Parameter TDX-1 Calibration Goals
Absolute radiometric accuracy < 0.7dB
Internal calibration accuracy ≤ 0.1dB / ≤ 1.0 degree
Pixel localization accuracy ≤ 0.5m (range/azimuth)
Pointing accuracy < 2 mdeg (azimuth)
< 10 mdeg (elevation)
Antenna model accuracy ≤ 0.2 dB (requirement)
IGARSS 2010, Honolulu 29.07.2010
Slide 15
CALIBRATION
2.5 months (summer 2010)1. Geometric calibration2. Antenna pointing3. Antenna model4. Radiometric calibration
StripMap and ScanSAR
Cal test sites* Rainforest: distributed field* South Germany: 30 calibration sites from which 17 are permanently installed corner reflectors
TanDEM-X calibration team32 DLR colleagues
Around 60 calibration campaignswith reference point targets:transponders and cornersMore than 1000 datatakeswill be analyzed
TDX-1 Monostatic Calibration Strategy
IGARSS 2010, Honolulu 29.07.2010
Slide 16
CALIBRATION
D01
x
D02
x D03 xD04
xD05
x
D06x
D07x
D24-D30
x x
x
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
Calibration Field in South Germany near by Oberpfaffenhofen
Munich
IGARSS 2010, Honolulu 29.07.2010
Slide 17
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 for bistatic operation
Similar spectrograms
IGARSS 2010, Honolulu 29.07.2010
Slide 18
CALIBRATION
First results TDX-1: TRM Characterization – PN Gating
blue: measured in flight coldred: measured in flight hotblack: on ground characterization
Receive
Ph
ase
[deg
rees
]A
mp
litu
de
[dB
]
Transmit
Ph
ase
[deg
rees
]A
mp
litu
de
[dB
]
Warm instrument stability
IGARSS 2010, Honolulu 29.07.2010
Slide 19
CALIBRATION
First Results TDX-1: Antenna Pattern over Rainforest
Within requirements
strip_003 strip_004 strip_005 strip_006
strip_003 strip_004 strip_005 strip_006
IGARSS 2010, Honolulu 29.07.2010
Slide 20
CALIBRATION
First Results TDX-1: Antenna Pattern by Ground Receivers
Ground Receiver
PositionVector
Transmit pattern only
Relative accuracy< ± 0.1dB
Measurements confirmsimulated reference pattern
Within requirements
IGARSS 2010, Honolulu 29.07.2010
Slide 21
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 TDX-1 – TSX-1
RX
IGARSS 2010, Honolulu 29.07.2010
Slide 22
CALIBRATION
Questions?
THE END
TSX-1 DLR logo experiment: Oberpfaffenhofen, Bayern, Germany (19th June 2008)