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

2. Page 2ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

3. Page 3ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

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

6. Page 6ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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  o

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

8. Page 8ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

9. Page 9ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Range Power Profiles – IM/HH VV 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?

10. Page 10ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

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

13. Page 13ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

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

16. Page 16ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

18. Page 18ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

20. Page 20ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

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

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

24. Page 24ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002  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 External Characterization Results (2)  Good agreement with boresight from synthesized IS0 beam VV

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

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

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

28. Page 28ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 380  s

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