Sentinel-1A Radiometric Calibration

Transcription

1 Sentinel-1A Radiometric Calibration Peter Meadows 1, Alan Pilgrim 1, Riccardo Piantanida 2, Davide Riva 2, Nuno Miranda 3 (1) BAE Systems Applied Intelligence, West Hanningfield Road, Great Baddow, Chelmsford, Essex, CM2 8HN, United Kingdom. peter.meadows@baesystems.com (2) ARESYS S.R.L., Via Flumendosa, Milano, Italy. riccardo.piantanida@aresys.it, davide.riva@aresys.it (3) European Space Agency, ESRIN, via Galileo Galilei, Frascati, Italy. nuno.miranda@esa.int CEOS SAR Workshop, ESA/ESTEC, October

2 Outline Introduction Impulse Response Function Analysis Polarimetric Assessment and Ambiguity Analysis Absolute Radiometric Calibration Noise Equivalent Radar Cross-Section Auxiliary Data File Updates Image Anomalies User Queries User Documentation CEOS SAR Workshop, ESA/ESTEC, October

3 Introduction MPC Expert Support Laboratory Radiometric Calibration Responsible for quality assessment and calibration of all Sentinel-1 Level 1 products. Working closely with the MPC Coordination Centre, other ESLs and ESA. CEOS SAR Workshop, ESA/ESTEC, October

4 Impulse Response Function Analysis Measurements performed using DLR transponders & corner reflectors, BAE Corner Reflector and the Australian Corner Reflector Array. Results using data acquired since 1 st November Example impulse response function and spectra from the BAE CR: Sidelobe ratios: CEOS SAR Workshop, ESA/ESTEC, October

5 Impulse Response Function Analysis Azimuth Spatial Resolution CEOS SAR Workshop, ESA/ESTEC, October

6 Impulse Response Function Analysis Azimuth Spatial Resolution DLR Transponder D41 CEOS SAR Workshop, ESA/ESTEC, October

7 Impulse Response Function Analysis Azimuth Spatial Resolution CEOS SAR Workshop, ESA/ESTEC, October

8 Impulse Response Function Analysis Range Spatial Resolution CEOS SAR Workshop, ESA/ESTEC, October

9 Polarimetric Assessment and Ambiguity Analysis Polarimetric Cross-Talk derived from DLR & BAE Corner Reflectors: CEOS SAR Workshop, ESA/ESTEC, October

10 Polarimetric Assessment and Ambiguity Analysis Polarimetric Channel Coregistration using ESA & DLR transponders: Azimuth ambiguities using ESA & DLR transponders: CEOS SAR Workshop, ESA/ESTEC, October

11 Polarimetric Assessment and Ambiguity Analysis Range ambiguities only seen in a very small number of products: CEOS SAR Workshop, ESA/ESTEC, October

12 Polarimetric Assessment and Ambiguity Analysis The mean range ambiguity ratio is -25.1±4.2dB. CEOS SAR Workshop, ESA/ESTEC, October

13 Absolute Radiometic Calibration The relative radar cross-section of the DLR transponders has been used to assess the radiometric calibration of S1-A (acquisitions since 1st Nov 2014): CEOS SAR Workshop, ESA/ESTEC, October

14 SM (S1, S3 & S6) CEOS SAR Workshop, ESA/ESTEC, October

15 IW CEOS SAR Workshop, ESA/ESTEC, October

16 EW CEOS SAR Workshop, ESA/ESTEC, October

17 Absolute Radiometric Calibration Summary tables showing mean relative RCS (db): VH VV HH HV S1-0.56±0.35 (11) 0.24±0.22 (11) -0.45±0.25 (13) 0.19±0.19 (13) S3-0.94±0.38 (10) -0.59±0.26 (10) -0.26±0.17 (12) 0.05±0.25 (12) S6-0.43±0.35 (9) 0.18±0.21 (9) 0.07±0.24 (17) 0.57±0.13 (17) VH VV HH HV IW 0.16±0.37 (23) 0.87±0.28 (23) 0.65±0.28 (17) 1.08±0.19 (17) EW -0.65±0.45 (80) 0.42±0.46 (81) -0.44±0.38 (54) 0.35±0.27 (54) CEOS SAR Workshop, ESA/ESTEC, October

18 Absolute Radiometric Calibration IW1 IW2 IW3 VH 0.07±0.37 (9) 0.22±0.17 (5) 0.22±0.46 (9) VV 0.71±0.30 (9) 1.07±0.08 (5) 0.92±0.25 (9) HH 0.71±0.19 (7) 0.93±0.23 (3) 0.48±0.27 (7) HV 0.95±0.11 (7) 1.36±0.02 (3) 1.09±0.17 (7) EW1 EW2 EW3 EW4 EW5 VH -0.72±0.40 (41) -0.73±0.43 (10) -0.63±0.40 (11) -0.51±0.58 (10) -0.40±0.57 (8) VV 0.53±0.40 (42) -0.06±0.29 (10) 0.13±0.28 (11) 0.50±0.48 (10) 0.76±0.55 (8) HH -0.59±0.29 (36) -0.30±0.14 (4) 0.11±0.22 (5) -0.10±0.44 (5) -0.34±0.47 (4) HV 0.27±0.25 (36) 0.33±0.11 (4) 0.58±0.11 (5) 0.60±0.29 (5) 0.54±0.18 (4) CEOS SAR Workshop, ESA/ESTEC, October

19 Absolute Radiometric Calibration An array of 40 corner reflectors have been deployed near Brisbane, Australia as a component of the Australian Geophysical Observing System (AGOS). The CRs of are size 1.5m (34), 2.0m (3) and 2.5m (3) with fixed orientations. Example IW oversampled response CEOS SAR Workshop, ESA/ESTEC, October

20 Absolute Radiometric Calibration The S1 relative RCS offset is due to the elevation pointing of the CRs (theoretical RCS curve for a trihedral curve assumes that the CR Azimuth offset is zero): The standard deviation of individual CRs can be ~0.1 db: See talk on Thursday at 12:00 for more results. CEOS SAR Workshop, ESA/ESTEC, October

21 Absolute Radiometric Calibration Permanent Scatter results for a stack of 15 images acquired in SM S6 mode over the Chicago calibration site: Values have been represented as provided by PSC tool, i.e. with the first value set to 0 db Standard deviation 0.15dB Results combined with AU Corner Reflectors. Both the RCS and the PSC values have been represented prior removal of their mean values CEOS SAR Workshop, ESA/ESTEC, October

22 Absolute Radiometric Calibration Permanent Scatter results for a stack of 22 images acquired in IW mode over the Milan calibration site: Values have been represented as provided by PSC tool, i.e. with three independent estimations for the three sub-swaths and with the first values set to 0 db Standard deviation 0.11dB Results combined with AU Corner Reflectors. Both the RCS and the PSC values have been represented prior removal of their mean values CEOS SAR Workshop, ESA/ESTEC, October

23 Noise Equivalent Radar Cross-Section Comparison of measurements from low backscatter imagery and NESZ predictions: S1 S2 S3 S4 CEOS SAR Workshop, ESA/ESTEC, October

24 Noise Equivalent Radar Cross-Section S5 S6 IW EW CEOS SAR Workshop, ESA/ESTEC, October

25 Noise Equivalent Radar Cross-Section IW1 IW2 Although S1-A products do not have noise removed, the headers include sufficient information for users to removed the NESZ if required (in the form of noise LUTs) CEOS SAR Workshop, ESA/ESTEC, October

26 Auxiliary Data File Updates ADFs are configuration files used with the SAR Processor. Updates indicate the continued improvement in the quality of Sentinel-1A products. During 2015, the following updates have been performed: CEOS SAR Workshop, ESA/ESTEC, October

27 A new set of ADFs are generated for each Radar Data Base update to ensure all historical data can be re-processed if required. ADFs are available from the Seninel-1 QC web site ( CEOS SAR Workshop, ESA/ESTEC, October

28 Image Anomalies Few examples of radio interference: S1A_IW_GRDH_1SDV_ T171526_ T171555_008137_00B6BD_A92D.SAFE CEOS SAR Workshop, ESA/ESTEC, October

29 Image Anomalies Unusual anomaly lasting a few minutes: See talk at 17:20 today for an explanation. S1A_IW_SLC 1ADV_ T165644_ T165711_007291_009FF3_1C25.SAFE S1A_IW_SLC 1ADV_ T165709_ T165737_007291_009FF3_BEAC.SAFE S1A_IW_SLC 1ADV_ T165734_ T165801_007291_009FF3_A7D6.SAFE CEOS SAR Workshop, ESA/ESTEC, October

30 User Queries A very few user queries have been received. One of the more interesting was to understand the source of unusual bright features near Beijing, China: CEOS SAR Workshop, ESA/ESTEC, October

31 User Queries NE Beijing: several bright linear features seen: S1A_IW_GRDH_1SSV_ T222018_ T222047_002744_003146_8417 CEOS SAR Workshop, ESA/ESTEC, October

32 User Queries Offset from train line indicates that the bright objects are trains. When radial velocity component reduces, the azimuth offset reduces (as expected). AZI S1A_IW_GRDH_1SSV_ T222018_ T222047_002744_003146_8417 CEOS SAR Workshop, ESA/ESTEC, October

33 User Documentation Sentinel-1 User Handbook Sentinel-1 Product Definition Sentinel-1 Level-1 Detailed Algorithm Definition Sentinel-1 Product Specification Sentinel-1 IPF Auxiliary Product Specification Sentinel-1 N-Cyclic Performance Reports Definition of the TOPS SLC deramping function for products generated by the Sentinel-1 IPF Sentinel-1 Radiometric Calibration of Products Sentinel-1 IPF: Impact of the Elevation Antenna Pattern Phase Compensation on the Interferometric Phase Preservation CEOS SAR Workshop, ESA/ESTEC, October

34 Thank you S1A_S1_GRDF_1SDH_ T062239_ T062303_002326_00273F_9E94.SAFE CEOS SAR Workshop, ESA/ESTEC, October