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CEOS 2010

SAR Performance of TerraSAR-X Mission with Two SatellitesBenjamin Bräutigam, Paola Rizzoli, Carolina González, Donata Polimeni, Dirk Schrank, Marco SchwerdtGerman Aerospace Center (DLR)Microwaves and Radar Institute

2CEOS 2010

StripMap Mode SpotLight Mode ScanSAR Mode

TerraSAR-X:• German Earth observation SAR satellite • X-band @ 9.65 GHz• 514 km dusk/dawn orbit• Multi-mode highly flexible operation• Public Private Partnership (PPP)• Launched on June 15 2007

Resolution: 1.5 m 1.5 mScene Size: 10 km x 5..10 km

Resolution: 3.3 m 3.3 mScene Size: 30 km x 50 km

Resolution: 17 m 18 mScene Size: 100 km x 150 km

3CEOS 2010

TerraSAR-X SAR System Parameters

Satellite TelemetryOrbit/attitude data (Doppler statistics)

Instrument temperatures

SAR Image ParametersRange of scene size and incidence angles

Resolution (geometric and radiometric)

Performance Parameters (PSLR/ISLR, NESZ)

4CEOS 2010

4.8 m

0.75

m

TerraSAR-X – Beam Specification

10 kmSingleDual

SpotlightHighRes

91 full perf122 total

Spotlight

15 km (15°-50°)13,5 km (50°-60°)

DualStripmap24 full perf54 total

Stripmap Near / Far

30 km (15°-50°)27 km (50°-60°)

SingleStripmapScanSAR

12 full perf27 total

Stripmap

Swath WidthPolarisationSAR Modes# of BeamsBeam Type

Over 1000 product variants -> Performance status over a sample!

Active phase antenna array

...1 2 3 12

12 panels in theazimuth direction

32 sub-arrayantennas per panel...

Electronic steering and shaping of acquisition beams (elevation and azimuth):

5CEOS 2010

Doppler Statistics

99% of the acquisitions concentrated inside ± 120 Hz

Mid-Range Doppler Plot

-3500

-3000

-2500

-2000

-1500

-1000

-500

0

500

1000

1500

01.01.2008

01.03.2008

01.05.2008

01.07.2008

01.09.2008

01.11.2008

01.01.2009

01.03.2009

01.05.2009

01.07.2009

01.09.2009

01.11.2009

01.01.2010

Date

Dop

pler

in [H

z]

HH Max HH MinVV Max VV MinHV Max VH Min

Maximum and minimum of mid-swath Doppler Centroid for each datatake / polarization channel

6CEOS 2010

Temperature Variations

-10

-5

0

5

10

15

20

25

30

35

01-01-08

03-02-08

07-03-08

09-04-08

12-05-08

14-06-08

17-07-08

19-08-08

21-09-08

24-10-08

26-11-08

29-12-08

31-01-09

05-03-09

07-04-09

10-05-09

12-06-09

15-07-09

17-08-09

19-09-09

22-10-09

24-11-09

27-12-09

Date

Tem

pera

ture

[ºC

]

PANEL_01 PANEL_02 PANEL_03 PANEL_04PANEL_05 PANEL_06 PANEL_07 PANEL_08PANEL_09 PANEL_10 PANEL_11 PANEL_12

Antenna Panel Temperature

No limit violation!

01.01.2008

01.03.2008

01.05.2008

01.07.2008

01.09.2008

01.11.2008

01.01.2009

01.03.2009

01.05.2009

01.07.2009

01.09.2009

01.11.2009

01.01.2010

Date

The temperature of the panelsis directly correlated with the

data load.

7CEOS 2010

SAR Image Analysis

Periodic acquisition of stripmap single-pol images40 data sets from October 2008 to December 20092 incidence angles / 2 bandwidths -> 2 locations

~25° incidence angle150 MHz

~38° incidence angle100 MHz

8CEOS 2010

Point Target Analyses

Impulse response of 1.5m corner reflector

9CEOS 2010

Point Target Analyses – Geometric Resolution

0

0,5

1

1,5

2

2,5

3

3,5

9.9.08 29.10.08 18.12.08 6.2.09 28.3.09 17.5.09 6.7.09 25.8.09 14.10.09 3.12.09 22.1.10

date

Geom

etr

ic R

eso

lution [

m]

38.9° inc. angle, desc 29.8° inc. angle, asc

Azimuth

Range

RangeAzimuthspec Azimuth spec Range

10CEOS 2010

Point Target Analyses – Peak-/Integrated Side Lobe Ratiog

-34

-32

-30

-28

-26

-24

-22

-20

-18

-16

9.9.08 29.10.08 18.12.08 6.2.09 28.3.09 17.5.09 6.7.09 25.8.09 14.10.09 3.12.09 22.1.10

date

PSLR

& I

SLR

[dB]

38.9° inc. angle, desc 29.8° inc. angle, asc

ISLR

PSLR

RangeAzimuthspec ISLR spec PSLR

11CEOS 2010

Distributed Target Analyses

12CEOS 2010

Distributed Target Analyses – Radiometric Resolution

Radiometric Resolution

0.00

1.00

2.00

3.00

4.00

5.00

6.00

7.00

29/9/08 28/11/08 27/1/09 28/3/09 27/5/09 26/7/09 24/9/09 23/11/09 22/1/10

Date

Rad

iom

etric

Res

olut

ion

[dB

]

25.71° inc. angle, ascending 38.75° inc. angle, descending

13CEOS 2010

Distributed Target Analyses – Noise Equivalent 0

NESZ analysis, distributed target and noise range profile

range

azim

uth

noise range profilesigma 0 from plain water

NESZ specification

14CEOS 2010

TerraSAR-X Mission with TanDEM-X satellite

TanDEM-X satellite flies in helixformation close to TerraSAR-X satellite (from October 2010)

Baseline varies with the argument of latitude due to helix formation

TerraSAR-X mission has fixedfootprints for repeat pass images

TDX pattern shifted w.r.t. TSX patterndepending on cross-track distance

Roll steering is going to minimize theshift in the pattern (NESZ impact)

15CEOS 2010

TanDEM-X Satellite – Roll Steering impact

Baseline250 m500 m1 km

Kind of beamstripstrip dualspot

Optimization for one baseline and one beam, i.e. one angle 31.5°

roll1.0 dB 0.1 dB

Up to 1 dB worse NESZ!with roll steering:

up to 0.1 dB worse NESZ!

16CEOS 2010

Allowed TDX pattern deviation for baseline variation: 0.2 dB

Maximal NESZ Deviation for Varying Baselines

Optimization is for fixed baseline

400 m600 m

800 m1000 m1200 m

200 m

0.2

17CEOS 2010

Conclusions

TerraSAR-X is in orbit since 2007

Over 40000 images have been successfully commanded and aquired

SAR system is being monitored for its performance and instrumentstability:

Doppler and Temperature statistics

Point Target Analyses

Distributed Target Analyses

The system shows no trends or performance degradation

With the extension of the mission by the TanDEM-X satellite, the roll steering technique will keep the product performance.