ASAR Processing Facility Status Processor releases Internal calibration

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 1

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 PF-ASAR v 3. 01 Installation Date 13 -09 -2002 PF-ASAR v 3. 02 12 -11 -2002 PF-ASAR v 3. 03 Next week !! ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 2

Internal Calibration Updates § High variations detected on the instrument gain calculated from the calibration pulses specially in WS – SS 4 and SS 5 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 3

Internal Calibration Updates § Strong modulation in the P 2 (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 P 2 amplitude in SS 4 P 2 amplitude in SS 5 Calculated Elevation Gain ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 4

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 5

Calibration Pulse Compression P 2 extracted Phase with extracted chirp P 2 extracted Phase with nominal chirp ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 P 2 Phase standard deviation SS 5 elevation gain nominal - extracted 6

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 IS 2 wave calibration constant 47. 38 d. B ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 7

Alternating Polarization Internal Calibration § P 1 pulses are saturated for some rows and P 2 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 IS 5 and IS 7. Refinement is needed for the rest of swaths Different calibration constant values per beam ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 8

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 9

Processing Parameters Update: IM Beam Fraction bandwidth (16 MHz) Gain (linear) 1. 0 Processed Bandwidth 16. 0 MHz IS 1 IS 2 1. 0 16. 0 MHz 8. 0 E 5 IS 3 0. 8 12. 8 MHz 8. 99 E 5 IS 4 0. 67 10. 72 MHz 9. 74 E 5 IS 5 0. 6 9. 6 MHz 10. 4 E 5 IS 6 0. 55 8. 8 MHz 10. 8 E 5 IS 7 0. 51 8. 16 MHz 11. 2 E 5 8. 0 E 5 § 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 10

Processing Parameters Update: AP § APP/ APG / APM processing gains update in order not to saturate the transponders and maximize the cross-polarization values Beam IS 1 IS 2 IS 3 IS 4 IS 5 IS 6 IS 7 Gain 2. 0 d. B 5. 0 d. B Beam IS 1 Gain 14. 3 d. B IS 2 14. 3 d. B IS 3 14. 3 d. B IS 4 14. 3 d. B IS 5 14. 3 d. B IS 6 14. 3 d. B IS 7 14. 3 d. B § 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 11

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 Beam Transmitted Bandwidth Look Bandwidth Number of Looks Beam WSM Gain GMM Gain SS 1 10. 15 42. 66 SS 2 9. 5 35. 75 SS 3 1. 0 35. 40 SS 1 14. 75 MHz 3. 35 MHz 7 SS 2 12. 86 MHz 2. 80 MHz 7 SS 3 10. 48 MHz 2. 38 MHz 7 SS 4 9. 54 MHz 2. 06 MHz 7 SS 4 9. 4 34. 40 SS 5 8. 48 MHz 1. 90 MHz 7 SS 5 9. 9 33. 46 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 12

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 13

Solution to Specan IRF degradation § Problem affecting the range response of ALL products processed with the Specan algorithm § § ASA_IMM_1 P ASA_APP_1 P ASA_APG_1 P ASA_WSM_1 P ASA_GMM_1 P ASA_APM_1 P § 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 14

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 d. B) and obtain consistent azimuth resolution for all the beams (~120 m) § Updated embedded row patterns: slight normalization variation Beam SS 1 SS 2 SS 3 SS 4 SS 5 Number of pulses / burst 50 65 55 71 60 ENVISAT Cal/Val Workshop – ESRIN – 9/13 December 2002 15

Auxiliary Parameters Update § ASA_XCA_AX § Updated calibration constants from the cal / val review results § Updated co- and cross-polarization antenna patterns (HV-IS 3, IS 6 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 16

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 17

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 18

Conclusions § Processor installed on the PDS generating ALL Level 1 b 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 19

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 20