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L2OS RFI status

This document outlines the RFI (Radio Frequency Interference) detection processes for L2OS products, specifically during the 2013 monitoring period in the Arctic region. It details the various flags and thresholds involved in identifying RFI from NIR measurements, focusing on the analysis of both Y and X polarizations. Key methodologies include snapshot analysis, outlier detection, and snapshot standard deviation tests. The report emphasizes the importance of robust threshold settings and validation of measurement data to improve RFI detection efficiency in satellite-derived datasets.

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L2OS RFI status

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  1. L2OS RFI status Nicolas Lamquin, Jean-Luc Vergely Jacqueline Boutin Paul Spurgeon ICM, Barcelona, 16/17 May 2013

  2. Version of products: • v600 source: sources-L2OS-core-v6.00.tar.gz • job orbit: descending SM_TEST_MIR_SCSF1C_20110505T040402_20110505T045804_600_001_0 • L1c flag description : SO-TN-IDR-GS-0005 (24/10/2012) • CNFOSF file: SM_TEST_AUX_CNFOSF_20050101T000000_20500101T000000_001_023_8 • RFI region: arctic RFI flags in v600 processing

  3. L1c RFI flags (measurement) • Fm_rfi_mitigation_tot (bit 7)  (v600) rfi_xx • analysis of NIR BT in X polarization • Fm_rfi_strong_tot (bit 15)  (v600) rfi_yy • analysis of NIR BT in Y polarization • Fm_rfi_tails_tot (bit 12)  never raised • affected by tails identified in the AUX_RFI list • Fm_rfi_point_tot (bit 16) • affected by point source identified in the AUX_RFI list

  4. L1c  L2 (DAP: measurements) • L2 flag « L1c_rfi »: True if any of L1c RFI flag True No RFI detection from NIR Y Tails in Fm_rfi_point_tot ? snapshot 34 (id:79011306): Fm_rfi_point_tot flag in L1c  L2 « L1c_rfi » is True

  5. green = RFI_XX True Y snap. 632 id:79012029 ? snap. 633 id: 79012031 X red = RFI_XX True and RFI_YY True snap. 634 id: 79012032

  6. L2 RFI flags (measurements) • Fm_rfi_L1 • Fm_l2_rfi • Fm_l2_rfi_outlier • Fm_l2_rfi_snapshot_out_of_range • Fm_l2_rfi_high_snapshot_std • Fm_l2_rfi_high_snapshot_std_st3 • Fm_l2_rfi_high_snapshot_std_st4

  7. L2 RFI flags (measurements) • Fm_l1c_rfi • Fm_l2_rfi • Fm_l2_rfi_outlier • Fm_l2_rfi_snapshot_out_of_range • Fm_l2_rfi_high_snapshot_std • Fm_l2_rfi_high_snapshot_std_st3 • Fm_l2_rfi_high_snapshot_std_st4  from L1c • True if Fm_l2_rfi_outlier or Fm_out_of_range, nominally • includes snapshot analysis below but not in current configuration gridpoint analysis (risk of RFI + RFI_nsig test)  local information per measurement • snapshot • analysis • raised for • complete • snapshot

  8. Fm_l2_rfi = Fm_l2_rfi_outlierOR Fm_out_of_range • Fm_out_of_range: threshold test on residual per measurement (Tm_out_of_range=50 K) • Fm_l2_rfi_outlier: analysis of all residuals per gridpoint (« risk of RFI ») + threshold test on residuals (comparison to std) snapshot 34 (id:79011306)

  9. extra points in Fm_l2_rfi = Fm_out_of_range • Fm_l2_rfi_outlier is not raised although Fm_out_of_range is raised  bRiskOfRFI seems not raised • sensitivity to examine (threshold 50 K) Sun tails ? snapshot 649 (id: 79012050)

  10. Fm_l2_rfi_snapshot_out_of_range • flags all snapshot if any Fm_out_of_range • does not proceed if some coast/ice nearby: set to True only if %(coast/ice) < Ts_snapshot_out_of_range Ts_snapshot_out_of_range = 20%  test threshold

  11. Fm_l2_rfi_snapshot_out_of_range example 1 snapshot 34 (id:79011306): Land contamination : Snapshot flag not raised example 2 snapshot 649 (id: 79012050):

  12. Fm_l2_rfi_high_snapshot_std Fm_l2_rfi_high_snapshot_std_st3 and Fm_l2_rfi_high_snapshot_std_st4 • snapshot standard deviation tests • per measurement in snapshot (« Fs_high_std... ») • propagates through complete snapshot • test 1: amount of data for statistics must be > Ts_meas_min (default: 35%) • test 2: sqrt(std / nMeas) > Ts_std (default: 2.5) • same threshold for « std », « std_st3 », and « std_st4 » •  refinement of threshold(s) ?

  13. for each configuration : process 1 month of data ? NO ! (too much thresholds to be tested) • tests on one orbits and do relative comparison : relative SSS, number of valid TBs …etc. • tests on several orbits in a (lat,lon) window in order to check the salinity estimation (comparison with ISAS maps). • after a choice of configuration : monthly test Test definition

  14. Remarks • would be useful to have snapshot_ID for all measurements in L2 DAP • need « Fs_high_std... » in DAP ? • DPM not coherent in 8_2-1 and 8_3-1 (OK in the code) • Some variables not defined in the DPM: RFI_c1, RFI_c2 • Fm_RFI_L1_tot (type ‘s’) in DPM ? (OK in the code : all L1c flags are used)

  15. L2OS RFI detectionDecision tree

  16. Introduction • Difference between outlier and RFI ? RFIs : unexpected physical source + Gibbs and tails Outliers : reconstruction problem ? - we expect snapshot signature for RFI and outlier - long time period contamination for RFI : seen by all the orbits which overpass the source : AUX_DGG_RFI information

  17. Flags in the decision tree if Fm_Resol(im,igp) or (Fm_outlier(im,igp) and not Fg_ctrl_suspect_RFI) or (Fm_L2_RFI(im,igp) and Fg_ctrl_suspect_RFI) or Fm_out_of_range(im,igp) or Fm_border_fov(im,igp) or Fm_Moon_SpecDir(im,igp) or Fm_gal_noise_error(im,igp) or Fm_sun_limit(im,igp) or Fm_L1c_sun(im,igp) then Fm_valid = false endif Fg_ctrl_suspect_RFI is raised if (number of Fm_L2_RFI==1 )/Na> Tg_num_RFI_max Fm_outlier : comes from comparison between TB_smos and TB_model corrected from a global shift applied at the dwell line level. nsigma comparison. Fm_L2_RFI : Fm_L2_RFI_outlier or Fm_L2_RFI_snapshot_out_of_range or Fm_L2_RFI_high_snapshot_std Fm_L2_RFI_outlier : comes from comparison between TB_smos and TB_model. RFI_nsigma comparison. Fm_outlier and Fm_L2_RFI_outlier very close: NO REASON TO USE DIFFERENT nsigma criteria (?). Proposition : suppress Fm_L2_RFI_outlier and keep only snapshot information for Fm_L2_RFI.

  18. INSTEAD OF : if Fm_Resol(im,igp) or (Fm_outlier(im,igp) and not Fg_ctrl_suspect_RFI) or (Fm_L2_RFI(im,igp) and Fg_ctrl_suspect_RFI) or Fm_out_of_range(im,igp) or Fm_border_fov(im,igp) or Fm_Moon_SpecDir(im,igp) or Fm_gal_noise_error(im,igp) or Fm_sun_limit(im,igp) or Fm_L1c_sun(im,igp) then Fm_valid = false Endif PUT : if Fm_Resol(im,igp) or Fm_outlier(im,igp) or (Fm_L2_RFI(im,igp) and Fg_ctrl_suspect_RFI) or Fm_out_of_range(im,igp) or Fm_border_fov(im,igp) or Fm_Moon_SpecDir(im,igp) or Fm_gal_noise_error(im,igp) or Fm_sun_limit(im,igp) or Fm_L1c_sun(im,igp) then Fm_valid = false Endif WITH Fm_L2_RFI(im,igp) : Fm_L2_RFI_snapshot_out_of_range or Fm_L2_RFI_high_snapshot_std

  19. Remarks • Fm_l2_RFI and Fg_ctrl_suspect_RFI do not integrate L1c RFI information • Fm_l2_RFI and Fg_ctrl_suspect_RFI do not integrate AUX_DGG_RFI information -> AUX_DGG_RFI and L1c information not used in the decision tree

  20. Extra slides

  21. OTT correction Snapshot out-of-range TB detection (PRP_8_2) -> Fs_out_of_range -> Fm_l2_rfi_snapshot_out_of_range Snapshot level Snapshot level Snapshot standard deviation tests (PRP_8_3) -> Fs_high_std -> Fm_l2_rfi_high_snapshot_std Measurement outlier detection (PRP_8_4) -> Fm_l2_RFI_outlier -> Fm_outlier Dwell line level RFI AUX detection (PRP_8_5) -> Fm_l2_RFI (from Fm_l2_RFI_outlier, Fm_l2_rfi_snapshot_out_of_range, Fm_l2_rfi_high_snapshot_std) -> Fg_ctrl_suspect_RFI Grid point level

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