th1.l10.2: tandem-x commissioning phase status

IGARSS 2010, Honolulu, 29th July

TanDEM-X Commissioning Phase Status

J. Hueso Gonzalez, M. Bachmann, H. Hofmann and

DLR commissiong phase team

IGARSS 2010, Honolulu 29.07.2010

Slide 2

New Challenges TanDEM-X Mission

Two satellites

System complexity increased

Close formation flying

Coordination TanDEM-X and TerraSAR-X mission acquisitions

Bi-static acquisitions and processing chain

Requirements for a high quality global DEM

Short duration of commissioning phase required

Limited nominal overlap

2.5 years for the DEM

TerraSAR-X2007 2008 2009 2010 2011 2012 2013 2014 2015

TanDEM-X

DEM Acquisition

CP


Slide 3

Overview TanDEM-X Commissioning Phase Plan

20 km Formation Close Formation

TDX monostaticcommissioning phase

LEOP and GS checkout

Orbit drift

1 month 2,5 months

Launch 21.06.2010

Transition 20km 07.2010

Transition close formation 10.2010

2 months

Operational01.2011

Bistaticcommissioning phase

• Make satellite operational – monostatic and bistatic

• Verify specifications

• Ensure satellite safety in close formation


Slide 4

Launch and Early Orbit Phase (LEOP) &Ground Segment Checkout


Slide 5

TanDEM-X Launch – June 21st 2010

TanDEM-X launch video

http://www.youtube.com/watch_popup?v=1NZh2as9sOs&vq=medium


Slide 6

LEOP – Orbit configurations

TDX-1 insertion 15700 km behind TSX-1

Earth rotation and time delay: both satellites acquire different regionson the same pass

Approximation of TDX-1 640km/day

Objective: reach 20 km along track separation

Allows repeat pass interferograms

No interferences for monostatic calibration

510-515 kmHeight

~95 minPeriod

11 daysRepeat cycle

97.4°, polarInclination

TSX-1 and TDX-1reference orbit characteristics

TSX-1

TDX-1

15700 km20 km


Slide 7

LEOP & Ground Segment Checkout

Space segment checkout

Satellite activation

Boom deployment

First contacts, telemetry

Ground station checkout

Tracking, downlink, data distribution

Verification of orbit products: orbit position, attitude, baseline

Product ordering chain: planning, commanding and data dump

Thermal behaviour instrument

SAR processor checkout

required before starting the SAR system calibration


Slide 8

First SAR Images of TDX-1 – Ukraine

River Donets

Agricultural land types↕

Polarization response

24/06/2010; dual-pol SAR image; ascending orbit, right looking


Slide 9

First SAR Images of TDX-1 – Ukraine

vTDX-1

vTRAIN

Azimuth displacement moving target~ vTRAIN range

azimuth

range


Slide 10

TDX-1 Monostatic Commissioning –Pursuit Monostatic Formation

20 km


Slide 11

TDX-1 Monostatic Commissioning Phase

Profit from TSX-1 mission

Experience commissioning phase

TSX-1 with outstanding performance

Successful integration and verification of ground and space segment

Characteristics orbit

20 km along track separation: allow monostatic calibration

Helix formation – 300 m radial, 1305 m horizontalto compensate residual Earth rotation

Repeat pass acquisitions, same coverage,very small baseline

Duration 2.5 months


Slide 12

Mono-CP: Safety Aspects

Safe Formation Flight

Collision avoidance mechanisms

Maneuver execution, 1st helix formation

Acquisition Safe Mode (ASM): magnetic torquer mode

Exclusion Zone

Prevent mutual SAR illumination: damage electronics

Failure detection, isolation and recovery

Sync Warning & Inter-Satellite Link

TSX-1 – TDX-1 real time mutual health check

Contingency handling in ASM

Disable transmission when neighbor satellite is not nominal


Slide 13

Mono-CP: Calibration and Performance

SAR External Calibration

Campaigns for deploying point targets and rainforest acquisitions

Geometric, antenna model, radiometric

Internal Calibration

TRM accuracy and stability

Monitor instrument drift, replica quality

Overall SAR Performance

Commanding, timing, instrument settings

Radiometric parameters: NESZ, ASR, resolution

Product Verification

Doppler centroid and pointing verification

Image quality, coverage

Ensure quality for TerraSAR-X mission products


Slide 14

Bistatic Commissioning –Close Formation


Slide 15

Bi-static Commissioning Phase

Duration: 55 days

Close formation 0m average along track 500m cross-track baseline

First bistatic cycle

Ground stations network

Roll steering

Complete bistatic chain: order, commanding, processor

Baseline offset calibration

DEM calibration tests

Flight Qualification Review

Nominal DEM acquisition should begin


Slide 16

TanDEM-X Global Test Sites

0° - Equator

30°N

60°N

30°S

60°S


Slide 17

Highlights


Slide 18

Highlights

• Accurate injection in orbit

• Satellite control High attitude and orbit stability Successful Acquisition Safe Mode test

• First SAR image three days after launch

• First interferogram incorporating both satellites after 26 days

• Excellent status of the ground segment chains for TerraSAR-X and TanDEM-X acquisitions

CommandingProcessingDownlink

220 m± 2 kmAltitude

TDX-1ExpectedInjection parameter

0.0095 deg± 0.04 degInclination

No showstoppers at all!


Slide 19

TanDEM-X first interferogram and DEM (I)

Repeat pass on 15/07/2010: 48s/370 km separationLarge along track distance: different coverage due to Earth rotation

Convergence at the poles angular velocity Earth is reduced there

TSX-1

TDX-1

Ground tracks crossat the poles


Slide 20

TanDEM-X first interferogram and DEM (II)

Rotation of range-azimuth coordinatesGround spectra can be aligned by applying squint during acquisition

Observe the same portion of the azimuth spectrum

x (range)

y (a

zim

uth)

x‘

y‘

kx

k y Ground spectraacquired at zero-Doppler

Squint correction applied

Rotated SAR coordinates Rotated ground spectrum

-0.058º bkw squintdoppler -500 Hz

0.93º fwd squint

doppler 800 Hz


Slide 21

Results over October Revolution Island (Russian Arctic)

Coherence

DEM

SAR Image

Coherence

Interferogram

* Baseline: ~2600 m* hamb = 3m* DEM accuracy ≈ 10cm

No azimuth filter needed in interferometricprocessing


Slide 22

Questions?

THE END

th1.l10.2: tandem-x commissioning phase status

Documents

tandemx launch

coordination tandemx

sar images of tdx

passapproximation of

transition close formation

bistaticcommissioning

orbit position

monostatic calibration510