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L2OS RFI study

L2OS RFI study. 9 May 2011. ARGANS & L2OS ESL. Outliers & RFI. new 2 step RFI outlier detection algorithm based on reducing outlier threshold if high probability of RFI detected for pol = 0 to 3 /* Stokes 1..4 */ if std( TBmodel [ pol ] - TBsmos [ pol ]) > 1.2 * std_theory then

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L2OS RFI study

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  1. L2OS RFI study 9 May 2011 ARGANS & L2OS ESL

  2. Outliers & RFI new 2 step RFI outlier detection algorithm based on reducing outlier threshold if high probability of RFI detected for pol = 0 to 3 /* Stokes 1..4 */ if std(TBmodel[pol] - TBsmos[pol]) > 1.2 * std_theory then rfi_outlier_risk[pol] = TRUE if rfi_outlier_risk[pol] then for each measurement if abs(TBmodel[pol] - TBsmos[pol]) > 3 * rad_noise then Fm_L2_rfi = TRUE where std_theory = √ ((TB_radiometric_noise2 + TBmodel2 ) / nMeas) factor of 1.2 is 99% confidence with 100 measurements (1 + 0.18) nsig is reduced from 5 (non-RFI outlier detection threshold) to 3

  3. L2OS RFI detection (early version of algorithm) >200 km from land Fg_ctrl_suspect_rfi set if Fm_L2_RFI > 50%

  4. L2OS RFI detection (early version of algorithm) >40 km from land Fm_outlier never set because algorithm skipped outlier test if risk of RFI detected

  5. L2OS RFI detection (early version of algorithm) no RFI detection RFI detection Fm_L2_RFI higher % than Fm_outlier (ie more sensitive)

  6. L2OS RFI detection (early version of algorithm) no RFI detection RFI detection delta Problem: RFI detection works well, but impacts non-RFI retrievals, because measurements discarded if Fm_L2_RFI set even if < 50%

  7. Outliers & RFI – extended algorithm Dg_RFI_L2 = count(Fm_L2_rfi) if (Dg_RFI_L2 / Dg_num_meas_L1c) > Tg_num_RFI_max (50%) then Fg_ctrl_suspect_rfi = TRUE if Fg_ctrl_suspect_rfi then if Fm_L2_rfi then Fm_valid = false else /* use ‘normal’ non-RFI outlier test */ if Fm_outlier then Fm_valid = false

  8. L2OS RFI detection (current algorithm) Fg_ctrl_suspect_rfi set if Fm_L2_RFI > 50% Fm_outlier also set, even if risk of RFI detected Fm_L2_RFI higher % than Fm_outlier (ie more sensitive)

  9. L2OS RFI detection (current algorithm) no RFI detection RFI detection delta (= RFI – no RFI) Some additional retrievals in Arctic (> 200km from coast)

  10. L2OS RFI detection (current algorithm) no RFI detection RFI detection delta Additional retrievals in North Pacific & Arctic

  11. L2OS RFI detection (current algorithm) > 40km from coast > 200km from coast False RFI detection near Antarctic ice

  12. L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_20110425T185354_20110425T194756_317_001_1 (unfiltered)

  13. L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_20110425T185354_20110425T194756_317_001_1 (filtered: 44329/82665)

  14. L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_20110425T185354_20110425T194756_500_001_8 (filtered: 48522/82212) L2 RFI outlier test >40km

  15. L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_20110502T051050_20110502T060452_317_001_1 (unfiltered)

  16. L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_20110502T051050_20110502T060452_317_001_1 (filtered: 17957/62361)

  17. L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_20110502T051050_20110502T060452_500_001_8 (filtered: 21683/61963) L2 RFI outlier test >40km

  18. L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_20110430T085851_20110430T095250_317_001_1 (unfiltered)

  19. L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_20110430T085851_20110430T095250_500_001_8 Fg_ctrl_suspect_RFI

  20. L2OS RFI detection comparing 0317 & v500 SM_OPER_MIR_OSDAP2_20110430T085851_20110430T095250_317_001_1 (filtered: 17899/53953)

  21. L2OS RFI detection comparing 0317 & v500 SM_TEST_MIR_OSDAP2_20110430T085851_20110430T095250_500_001_8 (filtered: 21506/53520) L2 RFI outlier test >40km

  22. L2OS RFI detection comparing 0317 & v500 317 500 no RFI detection 500 with RFI detection SM_OPER_MIR_SCSF1C_20110313T055704_20110313T065103_346_001_1

  23. L2OS RFI detection comparing 0317 & v500 317 500 no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_20110413T141055_20110413T150454_317_001_1

  24. L2OS RFI detection comparing 0317 & v500 317 500 no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_20110413T155057_20110413T164459_317_001_1

  25. L2OS RFI detection comparing 0317 & v500 317 500 no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_20110413T164100_20110413T173501_317_001_1

  26. L2OS RFI detection comparing 0317 & v500 317 500 no RFI detection 500 with RFI detection SM_OPER_MIR_SCSF1C_ 20110413T041028_20110413T050427_346_001_1

  27. L2OS RFI detection comparing 0317 & v500 317 500 no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_20110313T200742_20110313T210141_317_001_1

  28. L2OS RFI detection comparing 0317 & v500 Fm_L2_RFI Fg_ctrl_suspect_rfi unfiltered filtered 317 500 no RFI detection 500 with RFI detection SM_OPER_MIR_OSDAP2_20110313T123721_20110313T133122_317_001_1

  29. Outliers & RFI • Conclusions • new L2 RFI algorithm detects RFI • once detected, RFI measurement selection enables &/or improves retrieved salinity • L1 coast contamination causes false RFI positives • RFI thresholds need tuning with new L1 • L2OS configuration can turn RFI detection/mitigation off if required

  30. Decision: RFI distance-to-coast >40km >200km SM_TEST_MIR_OSDAP2_20110313T005649_20110313T015043_318_001_8

  31. Decision: RFI distance-to-coast >40km >200km Set coast limit >40km & find good values for RFI_std, RFI_nsig &Tg_num_RFI_max with new L1PP

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