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 29.07.2010Slide 2

New Challenges TanDEM-X Mission

Two satellites

System complexity increasedClose formation flying Coordination TanDEM-X and TerraSAR-X mission acquisitionsBi-static acquisitions and processing chain

Requirements for a high quality global DEM

Short duration of commissioning phase requiredLimited nominal overlap2.5 years for the DEM

TerraSAR-X2007 2008 2009 2010 2011 2012 2013 2014 2015

TanDEM-X

DEM Acquisition

CP

IGARSS 2010, Honolulu 29.07.2010Slide 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

1. Make satellite operational – monostatic and bistatic2. Verify specifications3. Ensure satellite safety in close formation

IGARSS 2010, Honolulu 29.07.2010Slide 4

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

IGARSS 2010, Honolulu 29.07.2010Slide 5

TanDEM-X Launch – June 21st 2010

TanDEM-X launch video

IGARSS 2010, Honolulu 29.07.2010Slide 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 minPeriod11 daysRepeat cycle

97.4°, polarInclination

TSX-1 and TDX-1reference orbit characteristics

TSX-1

TDX-1

15700 km20 km

IGARSS 2010, Honolulu 29.07.2010Slide 7

LEOP & Ground Segment Checkout

Space segment checkoutSatellite activationBoom deploymentFirst contacts, telemetry

Ground station checkoutTracking, 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

IGARSS 2010, Honolulu 29.07.2010Slide 8

First SAR Images of TDX-1 – Ukraine

River Donets

Agricultural land types

24/06/2010; HH SAR image; ascending orbit, right looking

IGARSS 2010, Honolulu 29.07.2010Slide 9

First SAR Images of TDX-1 – Ukraine

vTDX-1

vTRAIN

Azimuth displacement moving target~ vTRAIN range

azimuth

range

IGARSS 2010, Honolulu 29.07.2010Slide 10

TDX-1 Monostatic Commissioning –Pursuit Monostatic Formation

20 km

IGARSS 2010, Honolulu 29.07.2010Slide 11

TDX-1 Monostatic Commissioning Phase

Profit from TSX-1 missionExperience commissioning phaseTSX-1 with outstanding performanceSuccessful integration and verification of ground and space segment

Characteristics orbit20 km along track separation: allow monostatic calibrationHelix formation – 300 m radial, 1305 m horizontalto compensate residual Earth rotationRepeat pass acquisitions, same coverage,very small baseline

Duration 2.5 months

IGARSS 2010, Honolulu 29.07.2010Slide 12

Mono-CP: Safety Aspects

Safe Formation FlightCollision avoidance mechanismsManeuver execution, 1st helix formationAcquisition Safe Mode (ASM): magnetic torquer mode

Exclusion ZonePrevent mutual SAR illumination: damage electronicsFailure detection, isolation and recovery

Sync Warning & Inter-Satellite LinkTSX-1 – TDX-1 real time mutual health checkContingency handling in ASMDisable transmission when neighbor satellite is not nominal

IGARSS 2010, Honolulu 29.07.2010Slide 13

Mono-CP: Calibration and Performance

SAR External CalibrationCampaigns for deploying point targets and rainforest acquisitionsGeometric, antenna model, radiometric

Internal CalibrationTRM accuracy and stability Monitor instrument drift, replica quality

Overall SAR PerformanceCommanding, timing, instrument settingsRadiometric parameters: NESZ, ASR, resolution

Product VerificationDoppler centroid and pointing verificationImage quality, coverage

Ensure quality for TerraSAR-X mission products

IGARSS 2010, Honolulu 29.07.2010Slide 14

Bistatic Commissioning –Close Formation

IGARSS 2010, Honolulu 29.07.2010Slide 15

Bi-static Commissioning Phase

Duration: 55 days

Close formation 0m average along track500m cross-track baseline

First bistatic cycleGround stations networkRoll steeringComplete bistatic chain: order, commanding, processorBaseline offset calibration

DEM calibration tests

Flight Qualification ReviewNominal DEM acquisition should begin

IGARSS 2010, Honolulu 29.07.2010Slide 16

TanDEM-X Global Test Sites

0° - Equator

30°N

60°N

30°S

60°S

IGARSS 2010, Honolulu 29.07.2010Slide 17

Highlights

IGARSS 2010, Honolulu 29.07.2010Slide 18

Highlights

1. Accurate injection in orbit

2. Satellite control High attitude and orbit stabilitySuccessful Acquisition Safe Mode test

3. First SAR image three days after launch

4. First interferogram incorporating both satellites after 26 days

5. 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!

IGARSS 2010, Honolulu 29.07.2010Slide 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

IGARSS 2010, Honolulu 29.07.2010Slide 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‘

kxk y Ground spectra

acquired 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

IGARSS 2010, Honolulu 29.07.2010Slide 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

IGARSS 2010, Honolulu 29.07.2010Slide 22

Questions?

THE END