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ASAR Processing Facility Status

ASAR Processing Facility Status. Processor releases Internal calibration updates Processing parameter updates Auxiliary Files updates Future development Conclusions. Josep Closa ESA-ESRIN. Processor Version. Installation Date. PF-ASAR v3.01. 13-09-2002. PF-ASAR v3.02. 12-11-2002.

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ASAR Processing Facility Status

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  1. ASAR Processing Facility Status • Processor releases • Internal calibration updates • Processing parameter updates • Auxiliary Files updates • Future development • Conclusions Josep Closa ESA-ESRIN ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  2. Processor Version Installation Date PF-ASAR v3.01 13-09-2002 PF-ASAR v3.02 12-11-2002 PF-ASAR v3.03 Next week !! Processor Releases • 3 new releases since the calibration workshop • All releases preceded by the delivery of a standalone version used to perform pre-validation before installation in the PDS • Last version (3.03) to be installed within next week • Products for the validation workshop processed with the latest standalone version ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  3. Internal Calibration Updates • High variations detected on the instrument gain calculated from the calibration pulses specially in WS – SS4 and SS5 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  4. Internal Calibration Updates • Strong modulation in the P2 (receive) calibration pulses not detected by the pulse filtering based on nominal amplitudes • Variation in the calculated gain due to wrong phase values extracted from the calibration pulses Elevation gain filtering based on nominal chirp energy values P2 amplitude in SS4 P2 amplitude in SS5 Calculated Elevation Gain ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  5. Calibration Pulse Compression • Calibration pulse compression to extract the phase initially performed with the reconstructed replica • Artefacts on the chirp reconstruction from any corrupted calibration pulse influence on the extracted phase • Calibration pulse compression performed with the nominal chirp ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  6. Calibration Pulse Compression P2 Phase standard deviation P2 extracted Phase with extracted chirp P2 extracted Phase with nominal chirp SS5 elevation gain nominal - extracted ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  7. Wave Mode Phase Estimation • Variations in the elevation gain due to noisy phase values introduced by the first sample in the calibration window • Phase average within the window discarding the first sample • Recalculation of the IS2 wave calibration constant 47.38 dB ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  8. Alternating Polarization Internal Calibration • P1 pulses are saturated for some rows and P2 calibration pulses are not present for some swaths for all calibration cycles: incorrect values of the elevation gain • Use of reference energy values for product normalization • Same values are used for the different polarization combination images • Nominal values not available for IS5 and IS7. Refinement is needed for the rest of swaths Different calibration constant values per beam ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  9. Processing Parameters Updates • Change of range processing parameters following the change in transmitted bandwidths to 16 MHz for IM / AP • Changes impact the characterization / quality of all the IM / AP products Image Mode • Change in the IMP/ IMG processing bandwidths to keep range resolution: decrease of the SNR • Variation of processing gain with beam to compensate for bandwidth throw out in order to keep previous calibration constant values • Intermediate versions generating IMP/IMG products with higher range resolution • Future processor update to apply range multilooking on high incidence swaths: Higher ENL and SNR ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  10. Beam Fraction bandwidth (16 MHz) Processed Bandwidth Gain (linear) IS1 1.0 16.0 MHz 8.0 E5 IS2 1.0 16.0 MHz 8.0 E5 IS3 0.8 12.8 MHz 8.99E5 IS4 0.67 10.72 MHz 9.74E5 IS5 0.6 9.6 MHz 10.4E5 IS6 0.55 8.8 MHz 10.8E5 IS7 0.51 8.16 MHz 11.2E5 Processing Parameters Update: IM • Total processed bandwidth for the IMM products set to 16 MHz • Number of looks in IMM increased from 5 to 10 overlapped looks: throughoutput implications • Future update to make the number of overlapped looks beam dependent • No change for the IMS products: all expected range resolutions values are ~9.22 m ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  11. Beam Beam Gain Gain IS1 IS1 14.3 dB 2.0 dB IS2 2.0 dB IS2 14.3 dB IS3 2.0 dB IS3 14.3 dB IS4 2.0 dB IS4 14.3 dB IS5 5.0 dB IS6 5.0 dB IS5 14.3 dB IS7 5.0 dB IS6 14.3 dB IS7 14.3 dB Processing Parameters Update: AP • APP/ APG / APM processing gains update in order not to saturate the transponders and maximize the cross-polarization values • Some products in intermediate versions affected by range modulations due to processing parameters different from instrument parameters • APM product number of range looks changed from 5 to 10 overlapped looks • Future development to include two overlapped looks in APP/APG and make the number of range looks beam dependent • No changes on the APS processing parameters: expected range resolution ~8.3 m ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  12. Beam Beam Transmitted Bandwidth WSM Gain GMM Gain Look Bandwidth Number of Looks SS1 10.15 42.66 SS1 14.75 MHz 3.35 MHz 7 SS2 9.5 35.75 SS2 12.86 MHz 2.80 MHz 7 SS3 1.0 35.40 SS3 10.48 MHz 2.38 MHz 7 SS4 9.4 34.40 SS4 9.54 MHz 2.06 MHz 7 SS5 9.9 33.46 SS5 8.48 MHz 1.90 MHz 7 Processing Parameters Update: WSM / GMM • Following the update in the transmitted bandwidths, the number of looks and the look bandwidths in range have been updated • Parameter changes guarantee consistent range resolution at the center of the swath and increase the ENL • Look overlap around ~40 % • Processing gains per beam modified to achieve radiometric continuity • No beam merging performed over the beam overlap area ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  13. Other Updates • Range Compression performed with the nominal chirp function • Detection of calibration pulses based on the amplitude thresholding • Solution to the generation of the cross spectra • Wave Mode Level 2 algorithm clean up • Wide Swath Doppler Ambiguity estimation from data instead of orbit • Alternating Polarization Doppler refinement based on azimuth antenna patterns turned on ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  14. Solution to Specan IRF degradation • Problem affecting the range response of ALL products processed with the Specan algorithm • ASA_IMM_1P • ASA_APP_1P ASA_APG_1P ASA_APM_1P • ASA_WSM_1P • ASA_GMM_1P • Problem solved by adding some zero padding to the RIVs and stitching the regions before looks extraction • Buffering problems introduced by the solution already solved ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  15. Beam Number of pulses / burst SS1 50 SS2 65 SS3 55 SS4 71 SS5 60 Auxiliary Parameters Update • ASA_INS_AX • Updated nominal calibration pulse amplitude and phase values • Updated chirp coefficients for 16 MHz transmitted chirp • Updated azimuth antenna patterns generated from MS • New instrument WSM number of burst per beam to avoid azimuth ambiguities ( < -21 dB) and obtain consistent azimuth resolution for all the beams (~120 m) • Updated embedded row patterns: slight normalization variation ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  16. Auxiliary Parameters Update • ASA_XCA_AX • Updated calibration constants from the cal / val review results • Updated co- and cross-polarization antenna patterns (HV-IS3, IS6 missing) • ASA_XCH_AX • Updated external characterization factors for both polarizations: slight normalization variation • ASA_CON_AX: No update ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  17. Open Issues - Future Development (1) • Number of extracted range looks to be set to 2 for IMP / IMG / APP / APG products • Number of extracted range looks to be beam dependent for IMP / IMG / IMM / APP / APG / APM products • Elevation gain calculated from the calibration pulses filtering based on difference with reference replica energy values • Dependency of the reference replica energy values with polarization • Solution to the stripline products Doppler estimates on the last slice of the product • Solution to minor anomalies in the annotations • GM inverse filter verification • Introduction of the scene altitude over WGS 84 to perform geometry calculations: Effects of incorrect antenna pattern correction can be noticed on high terrain areas ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  18. Open Issues – Future Development (2) • Altitude information needs to be passed to the processor to avoid radiometric errors ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  19. Conclusions • Processor installed on the PDS generating ALL Level 1b and Level 2 products with expected quality • Minor algorithmic and operational problems solved during the Commissioning Phase period • Internal calibration procedure has been updated to avoid most of calibration pulse artefacts: additional filtering is required • All ASAR products normalized with the equivalent chirp energy calculated from internal calibration except for AP where cal pulses are corrupted: use of reference values • Processing parameters have been updated to accommodate instrument bandwidth changes in IM/AP/WS products and improve product quality ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

  20. Conclusions • Auxiliary files have been updated with the latest antenna patterns and instrument characterization parameters • Minor modifications will be added to the processor in order to improve product quality (ENL & SNR) and avoid radiometric errors over high terrain areas ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002

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