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Page 1ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 ASAR Processing Facility Status  Processor releases  Internal calibration updates  Processing.

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Presentation on theme: "Page 1ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 ASAR Processing Facility Status  Processor releases  Internal calibration updates  Processing."— Presentation transcript:

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

2 Page 2ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 Processor Version Installation Date PF-ASAR v PF-ASAR v PF-ASAR v3.03Next week !!

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

4 Page 4ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 P2 amplitude in SS4 P2 amplitude in SS5 Calculated Elevation Gain Elevation gain filtering based on nominal chirp energy values

5 Page 5ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

7 Page 7ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 dB

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

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

10 Page 10ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 BeamFraction bandwidth (16 MHz)Processed Bandwidth Gain (linear) IS MHz8.0 E5 IS MHz8.0 E5 IS MHz8.99E5 IS MHz9.74E5 IS MHz10.4E5 IS MHz10.8E5 IS MHz11.2E5

11 Page 11ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 BeamGain IS12.0 dB IS22.0 dB IS32.0 dB IS42.0 dB IS55.0 dB IS65.0 dB IS75.0 dB BeamGain IS114.3 dB IS214.3 dB IS314.3 dB IS414.3 dB IS514.3 dB IS614.3 dB IS714.3 dB

12 Page 12ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 BeamTransmitted Bandwidth Look Bandwidth Number of Looks SS MHz3.35 MHz7 SS MHz2.80 MHz7 SS MHz2.38 MHz7 SS49.54 MHz2.06 MHz7 SS58.48 MHz1.90 MHz7 BeamWSM GainGMM Gain SS SS SS SS SS

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

14 Page 14ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 Solution to Specan IRF degradation  Problem affecting the range response of ALL products processed with the Specan algorithm  ASA_IMM_1P  ASA_APP_1PASA_APG_1PASA_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

15 Page 15ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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 BeamNumber of pulses / burst SS150 SS265 SS355 SS471 SS560

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

17 Page 17ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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

19 Page 19ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 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

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


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