TANDEM-X: DEM ACQUISITION IN THE THIRD YEAR ERA

TANDEM-X: DEM ACQUISITION IN THE THIRD YEAR ERA D. Borla Tridon, M. Bachmann, D. Schulze, C. J. Ortega Miguez, M. D. Polimeni, M. Martone and TanDEM-X Team Microwaves and Radar Institute, DLR 5 th International Conference on Spacecraft Formation Flying Missions and Technologies 29.05.2013

Slide 2 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Outline Overview about TanDEM-X Mission TanDEM-X Global DEM Acquisition Plan Current Acquisition Status (First and Second Year) Acquisition Plan for the Third Year Antarctica Difficult Terrain Conclusions

Slide 3 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Outline Overview about TanDEM-X Mission TanDEM-X Acquisition Plan Current Acquisition Status (First and Second Year) Acquisition Plan for the Third Year Antarctica Difficult Terrain Conclusions

Slide 4 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era TerraSAR-X-add-on for Digital Elevation Measurements Overall Mission Goals acquisition of a global DEM according to Level-3 standard generation of local DEMs with Level-4 like quality demonstration of innovative bistatic imaging techniques and applications TerraSAR-X / TanDEM-X: German Earth observation SAR satellites Public Private Partnership (PPP) X-band @ 9.65 GHz Multi-mode highly flexible operation TSX-1 Launched on June 2007 TDX-1 Launched on June 2010 514 km dusk/dawn orbit Spatial Resolution Absolute Vertical Accuracy (90%) Relative Vertical Accuracy (point-to-point in 1 cell, 90%) DTED-1 90 m x 90m < 30 m < 20 m DTED-2 30 m x 30m < 18 m < 12 m TanDEM-X 12 m x 12m < 10 m < 2 m Level-4 6m x 6m < 5 m < 0.8 m Slide 4

Slide 5 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Helix Formation

Slide 6 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Cross-Track Interferometry for DEM Acquisition Image1 Image 2 Interferogram TerraSAR-X B φ TanDEM-X DEM Unwrapping H z

Slide 7 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Outline Overview about TanDEM-X Mission TanDEM-X Global DEM Acquisition Plan Current Acquisition Status (First and Second Year) Acquisition Plan for the Third Year Antarctica Difficult Terrain Conclusions

Slide 8 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era TanDEM-X Global DEM Acquisition Plan 2010 2011 2012 2013 2014 Commissioning phase 1 st global coverage 2 nd global coverage Additional Acquisitions & Special Science 1 st Global Coverage Small baseline (~200 m) HoA* ~ 45 m 2 nd Global Coverage Increased baseline (~300 m) HoA* ~ 30 m Combination: Dual Baseline Phase Unwrapping Improved Height Accuracy Additional Acquisitions (3 rd year) Difficult terrain to account for shadow & layover Different viewing geometry Antarctica Secondary Mission Goals Science acquisitions with special formations Higher resolution DEMs with local extend *HoA: Height of Ambiguity 2π Interferometric Phase

Slide 9 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Interferometric Coherence of 1 st Year 120000 scene (1 scene = 50x30 km 2 ) Mean land coherence: 91.8% higher than 0.6 ( Good -Quality Flag: 87.6%) Forest: Volume Decorrelation Deserts: Low SNR Solid Surface: High Coherence Mountains: Shadow/Layover

Slide 10 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Formation Flying Configuration 1st year 2nd year 3rd year Height of Ambiguity 2π Interferometric Phase large baseline small HoA small rel. height error Phase of libration: relative ascending node relative perigee

Slide 11 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era DEM Acquisition Timeline Derivation LandMask Beam definition Desired baseline (HoA) Helix Optimization Acquisition Timeline derivation: orbit usage Formation parameters Flight Dynamics (DLR-GSOC) Acquisition param.: PRF, duty cycle, energy, memory Performance param.: SNR, ambiguities, coherence Satellite resources/ downlink Acquisition parameters optimization TanDEM-X Timeline: start/stop time, beam TanDEM-X orders Mission Planning (DLR-GSOC)

Slide 12 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Outline Overview about TanDEM-X Mission TanDEM-X Global DEM Acquisition Plan Current Acquisition Status (First and Second Year) Acquisition Plan for the Third Year Antarctica Difficult Terrain Conclusions

Slide 13 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Antarctica Left-Looking acquisitions required -> low energy absorption by solar panels Acquisition in winter in Southern Hemisphere to avoid ice melt and low quality data Eclipse between May and August -> less energy on the solar panels => Acquisitions in the beginning of May Downlink & on-board memory limited (TDX:768 GBit, TSX:384 GBit) HoA O Higgins Vertical dist = 300 m Horizontal dist = 230 m

Slide 14 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Antarctica Left-Looking acquisitions over a radius of 1300 km Right-Looking acquisitions in the outer region

Slide 15 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Outline Overview about TanDEM-X Mission TanDEM-X Global DEM Acquisition Plan Current Acquisition Status (First and Second Year) Acquisition Plan for the Third Year Antarctica Difficult Terrain Conclusions

Slide 16 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Difficult Terrain: Deserts and Mountainous Regions to be acquired in the Third Year - Shadow and Layover - Desert

Slide 17 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Difficult Terrain: Mountainous Regions Steep and rough surfaces => Phase unwrapping errors => HoA > 85 m required Shadow and Layover effects

Slide 18 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Difficult Terrain: Mountainous Regions Steep and rough surfaces => Phase unwrapping errors => HoA > 85 m required Ascending Andes Shadow and Layover effects => Different viewing geometry: North descending / South ascending Shadow Shadow Layover Descending

Slide 19 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Difficult Terrain: Deserts Deserts: low SNR => low coherence => high relative height error Sandy deserts require small incidence angle: between 14 o and 28 o (nominal 28 o 48 o ) Rocky deserts present difficult topography => acquisition with different viewing geometry as for mountainous regions

www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Formation Flying Configuration Larger HoA -> smaller baselines: Vertical dist. > 250 m Horizontal dist. > 120 m Minimum baseline: 100 m Different geometry -> Change in exclusion zones -> Change in the Phase of Libration by 180o (to transmit with both satellites) 1st year 2nd year 3rd ϕ = 20o year Baseline between TSX-1 and TDX-1 only 150m Radial[m] Slide 20 ϕ = 200o Cross Track [m] Phase of libration: relative ascending node relative perigee

Slide 21 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Formation Flying Configuration Larger HoA -> smaller baselines: Vertical dist. > 250 m Horizontal dist. > 120 m Minimum baseline: 100 m Different geometry -> Change in exclusion zones -> Change in the Phase of Libration by 180o (to transmit with both satellites) Radial[m] ϕ = 20o oo 200 ϕ = 20 ϕ = 200o Cross Track [m] Vertical dist = 300 m Horizontal dist = 230 m Phase of libration: relative ascending node relative perigee

Slide 22 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Outline Overview about TanDEM-X Mission TanDEM-X Global DEM Acquisition Plan Current Acquisition Status (First and Second Year) Acquisition Plan for the Third Year Antarctica Difficult Terrain Conclusions

Slide 23 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era TanDEM-X Global DEM Acquisition Plan 2010 2011 2012 2013 2014 Commissioning phase 1 st global coverage 2 nd global coverage Additional Acquisitions & Special Science 2013 2014 May August April July 1 st Antarctica higher HoA Difficult terrain X 2 2 nd Antarctica lower HoA Science

Slide 24 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Conclusions The TanDEM-X mission will deliver a global DEM with unprecedented accuracy Stable operations in close formation 1 st global coverage completed in March 2012, 2 nd global coverage in April 2013 Antarctica acquisitions in Left-Looking mode in May-June 2013 Difficult terrain acquisitions from August 2013 Mountainous regions - shadow and layover effects => different viewing geometry Deserts: low SNR => steeper incidence angles

Slide 25 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Thank you for your attention!

Slide 26 www.dlr.de, D. Borla Tridon: TanDEM-X DEM Acquisition in the Third Year Era Acquisitions for the 1 st and 2 nd Coverage