TanDEM-X Interferometric Processing Chain and SAR Products. Thomas Fritz H. Breit, M. Eineder, M. Lachaise & ITP Development Team

Transcription

1 TanDEM-X Interferometric Processing Chain and SAR Products Thomas Fritz H. Breit, M. Eineder, M. Lachaise & ITP Development Team TanDEM-X Science Meeting Nov. 2008

2 From Acquisitions to Products - The TanDEM-X InSAR Processing Chain Basics Higher level processing of operational acquisition modes only operational DEM generation for a specific subset of acquisition modes Systematic processing of all mission data (~400 DEM scenes / day) Data driven processing starts when complete joint data take and all auxiliary products are available at processing system One type of products co-registered SSCs (CoSSCs) Processing into standardized archive products, retrieve them as delivery products via the catalogue No processing to different product variants from raw data on user request (unlike TS-X) Monostatic processing of active channel data to MGD,GEC,EEC, TerraSAR-X mission like products possible for restricted set of acquisitions Raw data of experimental modes can be processed with help from DLR scientists Slide 2

3 TanDEM-X DEM-, Operational and Experimental Acquisition Modes Classification of acquisitions in 4D mode space Imaging Mode of each instrument: SM, SL, HS, SC, (DRA-ATI, ) Polarization Mode of each instrument: Single, Dual, Twin, DRA-Quad IM geo pol Cooperative Mode of the two Instruments: bistatic, alternating bistatic, pursuit monostatic, none (TS-X mission) & experimental modes Formation Geometry: small or large along & across track separation / baseline coop DEMs Exp. Prod. Exp. Mode Slide 3

4 TanDEM-X Acquisition Modes and Products TanDEM-X Cooperative Mode (of TSX + TDX sats) Bistatic Operational Modes Alternating Bistatic Pursuit Monostatic Instrument Imaging Modes Stripmap (SM) Stripmap (SM) all basic modes Any Instrument Polarization Modes all basic modes single pol. all basic modes Any Formation Geometry Cross-track baselines < 4 km < 4 km < 4 km Any Along-track baselines < 1 km < 1 km Any (large ones) Any Processing and Products Experimental Modes Any oper. prod. exp. prod. TanDEM-X Screening L0 products All All All raw data ( + base annotation) DEM products SM single pol - SM single pol (fallback solution) Experimental products by ITP Experimental products by TerraSAR-X TMSP monostatic processing CoSSC + Interferogram TerraSAR-X L1b products* of monostatic channel 2 (Co)SSCs CoSSC for SM-S best effort (@ DLR) - 2 x TerraSAR-X L1b products* for all modes - best effort (@ DLR) *: The TerraSAR-X basic product spec does not apply in terms of performance Slide 4

5 DEM Acquisition & Processing Plan Year 1: full coverage with smaller baseline height ambiguity ~ 40 m good for moderate terrain Year 2: repeat with larger baseline height ambiguity ~ 30 m gives full accuracy robust Phase Unwrapping with supporting data from first year dual baseline PU Year 3: more baselines & angles to fill shadow and layover regions and support phase unwrapping of difficult areas maximum likelihood reconstruction method illumination DEM error swath shift clapboard pattern terrain slope / shadow & layover - - Slide 5

6 Integrated TanDEM-X Processor (ITP) ITP based on TerraSAR-X / TMSP & SRTM / InSAR-DEM heritage modular ITP executes the complete SAR InSAR DEM processing chain, invoked in different scenarios: 1. Basic SAR data parameter screening at the receiving stations 2. Fast quality check of joint TanDEM-X acquisitions 3. (Bistatic) SAR focussing to co-registered SSCs (CoSSCs) & InSAR processing & generation of Raw DEMs 4. Experimental product generation for operational modes (+ TMSP generated monostatic products) feedback loop with triggering from Mosaicking & Calibration Processor (MCP) for optimal uniform DEM product performance (reprocessing) Slide 6

7 Workflow Overview Ground Station Network Product Library DLR (PL) receiving station TanDEM-X Screener raw 1 raw 2 control system SAR InSAR PU / DEM TanDEM-X Screener - individual data take quality - joint (for planning) Raw DEM (re-)processing & multi-bl support data driven (In-)SAR Workflow triggering of (re-)processing & customized raw DEM generation PL RawDEMs CoSSCs MCP control MCP final DEM(s) DEM Workflow systematic & operator interaction Slide 7

8 TanDEM-X Processing Standard (By-)Products: Co-registered Single-look Slant-range Complex Products (CoSSCs) CoSSC common + RawDEM SSC ( TS-X L1b ) sat1 SSC ( TS-X L1b ) sat2 h S L ITP TanDEM-X acquisition for DEM generation DIMS PL: CoSSC Archive MCP internal use CoSSC delivery product Slide 8

9 ITP Bistatic Focussing operational bistatic DEM acquisitions are restricted to limited combinations of instrument modes & close formation flight with very small bistatic angles. main complication: sync pulse processing and timing corrections => ITP bistatic focussing uses pseudo-monostatic hyperbolic approach for DLR hybrid Chirp Scaling algorithm primarily interferometric mission => operational SAR processing is serving the InSAR system as pre-processing step common parameter estimation for focussing & InSAR phase preservation / phase synchronization co-registration of (passive) SSC to master common band & spectral shift filtering included in focussing steps Slide 9

10 TerraSAR-X / TanDEM-X: Interferometry Meets Stereo Radargrammetry Terrain Adaptive Coregistration coherence with classic polynomial co-registration not suited for high-res. X-band interferometry!!! major InSAR SW update [N. Adam]: Height difference bottom-peak: 1300 m coregistration (reference DEM & 76 fringes geometry. Refinement: signal correl.) 1.18 m slant range parallax 1.3 pixel misresgistration if not compensated! = complete loss of coherence Slide 10

11 ITP Dual (Multi)-Baseline Phase Unwrapping Use of Maximum Likelihood Estimator in slant range geometry -> Supported by reference phases from (SRTM-)DEM & Delta-k -> Interferogram with larger baseline is rescaled to master geometry Phases are unwrapped using their different PDF (noisy) unwrapped phase (2 BL) Pixel 1 PDFs of master and slave broad PDF of reference phase -> joint PDF (magenta) Phase gradients are used for spike reduction PDF of master and slave gradients ( pixel 1 pixel 2 ) joint PDF (blue) robust by MCF Ifgrm 1 with baseline B1 multi-baseline estimate Ifgrm 2 with baseline B2 pdf of phase difference -1/2 0 1/2-1/2 0 1/2 Δϕ [cycles/sample] scaling by B1/B2 Δϕ [cycles/sample] Pixel 2 (neighbor) wrong ambiguity (noise spikes) corrected unwrapped phase Slide 11

12 Delta-k Interferometry for additional PU Support Differential interferogram between 2 subbands at f C ±f 0 Generates interferogram with carrier frequency 2f 0 << f C For (150MHz) standard acquisitions: delta-k hamb ~ hamb x 96.5 (9.65 GHz / 100MHz) Phase unwrapping not necessary! Successfully tested with TS-X InSAR (R. Brcic) SAR 2 Δk phase scaling (wrapping) f_0 f_c SAR 1 Δr ambiguous unambiguous λ C λ C fc 2f 0 ESA ITT A Novel Approach for Wide-Band SAR Interferometry 3744 m/cycle 38.8 m/cycle height of ambiguity > ~1500m variation in topography Salar de Uyuni, Standard 150MHz Stripmap 14.09/ Two 50 MHz bandwidth subbands. Slide 12

13 oc es si ng Processing simulation setup mean=0.95 m σ =1.57 m Coherence PU errors Phase Dual TanDEM land Baseline 75 xpu 75 km r resulting error map (1 epbl) l ic at Laser DEM: Gars am Inn, Bavaria 5 km x 5 5m res. si m ul at pr Amplitude, Layover,Shadow In SA R io n Simulated TanDEM-X acquisitions (HELIX orbit, swathes, noise) io n try e m geo s tion a l i mu Slide 13

14 TanDEM-X PGS InSAR Processing Test Site Salar de Arizaro (Argentina) stable, highly coherent area, several interferometric pairs in different geometries (A/D, overlapping beams) acquired. July Dec 07: very few temporal changes (in blue)! Slide 14

15 TS-X InSAR: Single Baseline Phase Unwrapping Challenges TS-X Interferogram (1) height ambiguity: 7m coherence: 0.85 baseline: 830 m! i = 39 SRTM DEM TS-X DEM (1) σ = 25cm! at 5m posting but with significant PU errors Slide 15

16 TerraSAR-X InSAR: 2nd Baseline TS-X 2nd pair height ambiguity: 14 m coherence 2: 0.89 baseline 2: 450 m > op. TanDEM-X baselines Differences 1 st (7m hamb) 2 nd (14m hamb) DEM (atmosphere, baseline errors, fine structures, & PU errors in 1st DEM ) Slide 16

17 TanDEM-X Experimental Products: Co-registered SSCs CoSSC SSC ( TS-X L1b ) sat 1 common components SSC ( TS-X L1b ) sat 2 InSAR processing for bistatic SM only (e.g. dual pol) ITP x TanDEM-X acquisition for experimental product generation EOWEB catalogue orders: exp. CoSSC delivery product DIMS PL: CoSSC.experimental Archive Slide 17

18 Experimental Products as Co-registered SSCs CoSSC structure and format corresponds to 2 TS-X SSC L1b products (minor modifications) plus common components and annotation product performance strongly depends on acquisition conditions but is generally slightly reduced (w.r.t. TerraSAR-X mission products): common swath may deviate / drift common bandwidth processing reduces resolution bistatic channel not radiometrically calibrated (best effort) no add. sidelobe suppression (Hamming = 1.0), but: high geometric accuracy comprehensive annotation & coregistration allow straight-forward InSAR processing monostatic / active channel performance may be close to TS-X products Slide 18

19 Summary I Processing Chain Processing chain optimized for systematic generation of all raw DEM data for global HRTI-3 DEM within 2.5 years. Uniform raw DEM data performance guaranteed (multiple coverage, reprocessing) Unified processing system ITP for global DEM customized DEMs experimental products (+ TMSP) Bistatic SAR & InSAR - DEM processing has been successfully simulated for TanDEM-X conditions SAR & InSAR processing capabilities tested with real TS-X data Slide 19

20 Summary II - TanDEM-X Products operational DEM products: see presentation by B. Wessel operationally generated SAR products: experimental products from operational modes (co-registered complex images CoSSCs ) experimental mode raw data (processing with help from DLR contact scientist) TS-X mission basic products* from selected TanDEM-X raw data sets byproduct of operational DEM processing chain: archive of CoSSCs from all acquisitions for DEM generation (multi-temporal global coverage) *: TS-X basic product performance parameter specification does not apply Slide 20

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