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Antenna Elevation Pattern Estimation from Rain Forest Data

Antenna Elevation Pattern Estimation from Rain Forest Data. M. Zink ENVISAT Programme ESA-ESTEC. Content. Estimation Approach Fine-Tuning of VV patterns at ScanSAR sub-swath boundaries HH Beam Patterns VH Beam Patterns HV Beam Patterns Comparison with pre-launch patterns.

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Antenna Elevation Pattern Estimation from Rain Forest Data

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  1. Antenna Elevation Pattern Estimationfrom Rain Forest Data M. Zink ENVISAT Programme ESA-ESTEC ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  2. Content • Estimation Approach • Fine-Tuning of VV patterns at ScanSAR sub-swath boundaries • HH Beam Patterns • VH Beam Patterns • HV Beam Patterns • Comparison with pre-launch patterns ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  3. Estimation Approach • Based on IMP, WSM, (APM) products • Range power profile calculated applying simple threshold masking • Imaging geometry reconstructed from annotation parameters • Re-apply AP corrected in the processor • tan(inc) correction • Combined estimate from all available IM+WS products ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  4. 1474 1610 1975 2111 WS/VV Range Power Profiles at ECR • Approx. 0.5 deg around the beam merging region not used in estimation • Over-compensation at beam edges, especially SS1 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  5. new old Refined VV Patterns (SS1, IS3-IS6) ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  6. WS Profiles after Pattern Refinement 1474 1610 1975 2111 • Consistent slopes where the beams overlap • Absolute levels agree with cal factor from transponders and expected RF so ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  7. Sample Images HH ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  8. Elevation Beam Patterns - HH • Standard deviation of estimates <0.1dB • Even one homogeneous data set provides useful estimate • Maximum deviation from pre-launch patterns 0.5dB ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  9. Range Power Profiles – IM/HH HH • Gain correction via internal cal to be confirmed • IS1 profiles higher as for VV pol • Assumption on flat gamma profile at low incidence angles not valid? VV ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  10. Range Power Profiles – WS/HH • Consistent slopes where the beams overlap • Processing gains as for VV pol – different levels in SS4/SS5 • Absolute levels too high by 3dB because of problems in reading XCH file ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  11. Sample Images AP/VH ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  12. Elevation Beam Patterns - VH ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  13. Range Power Profiles – AP VV/VH • Reasonable flat co-pol profiles using patterns derived from IM/WS • Problems with cal pulses in some beams • Mixture of PDS data and products from instable standalone version ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  14. Sample Images AP/HV ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  15. Elevation Beam Patterns - HV ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  16. Range Power Profiles – AP HH/HV • Consistent processing based on reference energy levels for normalisation • No data for IS3&IS6 • Cross-pol ~6dB below co-pol ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  17. Range Power Profiles – AP ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  18. Difference Pre-Launch – RF Patterns / VV • Residual receiver gain droop would cause consistent near-to-far range trend • No trend visible • Confirmation of gain droop compensation ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  19. Difference Pre-Launch – RF Patterns • Accuracy of pre-launch measurement does not match highly accurate RF estimates • Limited control/knowledge of module gain/phase settings during pre-launch characterisation IS1 IS7 IS4 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  20. Conclusions • Elevation patterns for all beams – except HV IS3&IS6 • ScanSAR beams fine-tuned at beam boundaries • Absolute levels to be confirmed (internal cal corrections not fully reliable) • Cross-pol 6dB lower than co-pol • No residual gain droop effects • Difference to pre-launch patterns due to limitations in the on-ground characterisation ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  21. ASAR External Characterisation M. Zink & H. Jackson ENVISAT Programme ESA-ESTEC ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  22. P1 Ground Receiver External Characterization Mode • Cal Pulse P1 (cw) recorded onboard and by coherent ground receiver Tx Aux Radiating Row Signal BFN Tx Main Rx Main Cal BFN Cal Rx Aux ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  23. External Characterization Results (1) • Signal received by transponder • Phase from single column transmission is used to correct row stepping sequence ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  24. VV External Characterization Results (2) • Phase and amplitude difference between onboard recording and receiver measurements • Linear phase term due to off-boresight position of transponder • Residual linear phase due roll mispointing (offset between mechanical and electrical boresight) • Measured values [deg]: V: 0.070, 0.057, 0.066 H: 0.015, 0.011 • Good agreement with boresight from synthesized IS0 beam ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  25. External Characterization Results (3) • Consistent results for H pol from two measurements ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  26. Comparison ExChar Factors in V and H • higher amplitude variations across the 32 rows in H than V • Phase shows similar spread ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  27. Verification of ASAR ISP Datation • Requirement: 200 ms • RA-2 datation accuracy very similar: between -300 and –400 ms ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  28. Conclusions • Consistent measurements in both polarisations • Roll misalignment confirmed by pattern synthesis based on actual Module Stepping mode measurements • EC factors close to 1.0 and therefore small impact on elevation gain reconstruction • EC factors are different for H and V – different HW • ASAR datation error currently around 380ms ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  29. External Characterization Mode (2) • Single column transmission followed by row stepping sequence and single column transmission ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

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