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RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
RFI_in_PALSAR_data.pdf
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RFI_in_PALSAR_data.pdf

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  • 1. Characterization and Extent of Randomly-ChangingRadio Frequency Interference in ALOS PALSAR Data FJ Meyer1) 2), J Nicoll2), AP Doulgeris3) 1)Earth& Planetary Remote Sensing, University of Alaska Fairbanks 2)Alaska Satellite Facility (ASF) 3)University of Tromsø, Romssa Universitehta. N-9037 Tromsø, NorwayCollaborating Organizations:
  • 2. Outline • Motivation • An Uncharacteristic RFI Source in the American Arctic • Screening AADN’s PALSAR Archive for RFI Issues • Development of a Modified Notch Filter Approach for Signal Correction • Performance of Notch Filter Algorithm • ConclusionsIGARSS’11, Vancouver F. Meyer et al. 2
  • 3. Motivation • In American Arctic, polarimetric data regularly affected by signal artifacts causing huge variations of polarimetric signature (see examples below) • Initial survey showed: More than 80% of data over Barrow, AK affected • Source: High power RF interferenceIGARSS’11, Vancouver F. Meyer et al. 3
  • 4. An Uncharacteristic RFI Source in the American Arctic • DEW line and North Warning System: – Array of long-range and short-range over-the-horizon surveillance and early warning defense system of US and Canada – Originally ~ 90 sites located along American Arctic Coast – Migrated to North Warning System in 1985 and reduced to ~50 Sites Short-range stations Long-range stationsIGARSS’11, Vancouver F. Meyer et al. 4
  • 5. The Long Range Radar System FPS-117 • AN/FPS-117 Long Range Radar (Lockheed-Martin): – Pulsed phased array antenna system, with a PRF of up to 1500Hz – L-band frequency range of 1215-1400 MHz (PALSAR fc: 1270 MHz) – Low power, long range (up to 450km) – Randomly hopping among 18 channels in the 1215-1400 MHz band. Specifications frequency: 1215 - 1400 MHz pulse repetition frequency (PRF): 250 / 1100 Hz pulsewidth (PW): 100 / 800 µs peak power: 20 kW displayed range: bis 463 km Source: Lockheed-Martin beamwidth: β:3,4°, ε:2,7°IGARSS’11, Vancouver F. Meyer et al. 5
  • 6. Examples of Interference Signatures PALSAR PLR21.5: Orbit: 17260; Frame: 1440• Range-frequency azimuth-time representation: HH VV 6
  • 7. Examples of Interference Signatures PALSAR PLR21.5: Orbit: 17260; Frame: 1440 • Bandwidth and Power: – ~ 1 – 2.5 MHz bandwidth; fc changing on pulse-by-pulse basis HH VVIGARSS’11, Vancouver F. Meyer et al. 7
  • 8. Effects on SAR Imaging and Polarimetry PALSAR PLR21.5: Orbit: 17260; Frame: 1440• Focused SAR image without notch-filtering HH HV VV VH 8
  • 9. PALSAR Operational Notch Filter • Notch filtering during range compression: – Range FFT of block of 256 azimuth lines – Average spectrum along azimuth – Analyze gain for anomalies & apply notch filter if anomaly is detected – Then perform range and azimuth compression • Problem: – Due to the wide bandwidth and changing center frequency, anomalies difficult to detect by PALSAR notch filter →Especially in the cross-pol channels, PALSAR processor not able to provide sufficiently corrected dataIGARSS’11, Vancouver F. Meyer et al. 9
  • 10. Effects on SAR Imaging and Polarimetry PALSAR PLR21.5: Orbit: 17260; Frame: 1440• Focused SAR image with PALSAR operational notch-filtering HH HV VV VH 10
  • 11. A Simple RFI Screening Method • Per column of range compressed raw data, calculate coherence between odd and even samples:  f even f odd CLine    f even f even f odd f odd • This coherence is composed of SAR signal and RFI components CLine  CRFI  CSAR • CSAR is small and can either be ignored or identified in an averaging process • The plot to the right shows results where high coherence peaks correspond to RFI affected linesIGARSS’11, Vancouver F. Meyer et al. 11
  • 12. RFI Affected ALOS PALSAR Frames in the AADN Archive Severe Intermediate Not affectedIGARSS’11, Vancouver F. Meyer et al. 12 12
  • 13. RFI Affected ALOS PALSAR Frames in the AADN Archive Severe Intermediate Not affected Test Site AlaskaIGARSS’11, Vancouver F. Meyer et al. 13 13
  • 14. RFI Affected ALOS PALSAR Frames in the AADN Archive North Warning System Severe Intermediate Not affected Test Site AlaskaIGARSS’11, Vancouver F. Meyer et al. 14 14
  • 15. RFI Affected ALOS PALSAR Frames in the AADN Archive North Warning System Severe Intermediate Not affected Military Bases & Airport Radars Test Site AlaskaIGARSS’11, Vancouver F. Meyer et al. 15 15
  • 16. Notch Filtering based on Azimuth Analysis Original Data • Signatures are high power, narrow in azimuth time, wide bandwidth → detection based on azimuth analysis proposed • Workflow: Azimuth Time – Range compression – Range FFT – Cut through azimuth-time range-frequency diagram along azimuth – Detection of interference by local outlier analysis along azimuth – Notch filtering by removal of detected outliers – Azimuth compression Range FrequencyIGARSS’11, Vancouver F. Meyer et al. 16
  • 17. Notch Filtering based on Azimuth Analysis After Notch Filtering • Signatures are high power, narrow in azimuth time, wide bandwidth → detection based on azimuth analysis proposed • Workflow: – Range compression – Range FFT – Cut through azimuth-time range-frequency diagram along azimuth – Detection of interference by local outlier analysis along azimuth – Notch filtering by removal of detected outliers – Azimuth compressionIGARSS’11, Vancouver F. Meyer et al. 17
  • 18. Effects on SAR Imaging and Polarimetry PALSAR PLR21.5: Orbit: 17260; Frame: 1440• Focused SAR image without notch-filtering HH HV VV VH 18
  • 19. Effects on SAR Imaging and Polarimetry PALSAR PLR21.5: Orbit: 17260; Frame: 1440• Focused SAR image with azimuth analysis-based notch-filtering HH HV VV VH 19
  • 20. Effects on SAR Imaging and Polarimetry PALSAR PLR21.5: Orbit: 17260; Frame: 1440 HV No filter appliedIGARSS’11, Vancouver F. Meyer et al. 20
  • 21. Effects on SAR Imaging and Polarimetry PALSAR PLR21.5: Orbit: 17260; Frame: 1440 HV PALSAR Operational filterIGARSS’11, Vancouver F. Meyer et al. 21
  • 22. Effects on SAR Imaging and Polarimetry PALSAR PLR21.5: Orbit: 17260; Frame: 1440 HV Azimuth analysis-based filterIGARSS’11, Vancouver F. Meyer et al. 22
  • 23. Correction Results – Polarimetric Signature PALSAR PLR21.5: Orbit: 16837; Frame: 1440 Geographic Location Acquisition Date: March 23, 2009 RFI Source: Long Range Radar Station Pauli Decomposition Pauli Decomposition (LRRS) near Point Barrow, AK After Notch Filtering Before Notch FilteringIGARSS’11, Vancouver F. Meyer et al. 23
  • 24. Correction Results – Polarimetric Signature PALSAR PLR21.5: Orbit: 17085; Frame: 1440 Geographic Location Acquisition Date: April 09, 2009 RFI Source: Long Range Radar Station Pauli Decomposition Pauli Decomposition (LRRS) near Point Barrow, AK After Notch Filtering Before Notch FilteringIGARSS’11, Vancouver F. Meyer et al. 24
  • 25. Correction Results – Polarimetric Signature PALSAR PLR21.5: Orbit: 17260; Frame: 1440 Geographic Location Acquisition Date: April 21, 2009 RFI Source: Long Range Radar Station Pauli Decomposition Pauli Decomposition (LRRS) near Point Barrow, AK After Notch Filtering Before Notch FilteringIGARSS’11, Vancouver F. Meyer et al. 25
  • 26. Benefit of Developed RFI Filter for Polarimetric Classification of Sea Ice Features Operationally Processed Data Custom RFI-Filtered DataIGARSS’11, Vancouver F. Meyer et al. 26
  • 27. Benefit of Developed RFI Filter for Polarimetric Classification of Sea Ice Features After RFI Filtering → Quality of classification result visually improvedIGARSS’11, Vancouver F. Meyer et al. 27
  • 28. RFI monitoring by JERS-1 SAR (1992-1998)Normalized zero padded bandwidth (%) 0 10.0
  • 29. RFI monitoring by PALSAR (2010~2011)Normalized zero padded bandwidth (%) 0 10.0
  • 30. Conclusions and Recommendations: • L-band interference from over-the-horizon radars problematic in large parts of the American Arctic • Pulsed ground based systems cause temporarily narrow, high-power, and wide bandwidth interferences with randomly changing fc • Standard PALSAR processing scheme insufficient for removing interferences • A modified azimuth-based filtering algorithm shows good performance in removing RFI signals and restoring original data quality • Real data examples show successful mitigation of interferences • Polarimetric signatures after RFI filtering significantly improved • Growing issues of RFI in Microwave Remote Sensing needs to be addressedIGARSS’11, Vancouver F. Meyer et al. 30 30
  • 31. ANNOUNCEMENT: 2011 CEOS SAR Calibration and Validation Workshop Fairbanks, Alaska Workshop Dates: November 7 – 9, 2011 Abstract Deadline: September 14, 2011 More information at: www.asf.alaska.edu/ceos_workshop/IGARSS’11, Vancouver F. Meyer et al. 31 31
  • 32. Open Three Year PhD Position starting fall 2011 / spring 2012 for a radar remote sensing research project at the Geophysical Institute of the University of Alaska Fairbanks on Theoretical Investigations into the Impact and Mitigation of Ionospheric Effects on Low-Frequency SAR and InSAR Data Research Focus: • Investigation of spatial and temporal properties of ionospheric effects in SAR data • Development of statistical signal models • Design of optimized methods for ionospheric correction More information: Dr. Franz Meyer (fmeyer@gi.alaska.edu) and at: www.insar.alaska.eduIGARSS’11, Vancouver F. Meyer et al. 32
  • 33. Image and kml Creation • An average coherence is calculated per image. For example to the right C=0.010 (1.0% RFI coherence) • A kml bounding box is created and color coded according to interference severity (green=low RFI, yellow=moderate RFI, and red= high RFI).IGARSS’11, Vancouver F. Meyer et al. 33

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