SAOCOM Calibration Strategy

COMISION NACIONAL DE ACTIVIDADES ESPACIALES(The Argentinean National Commission of Space Activities)SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González,M. Thibeault, T. ZajcNovember 7 - 9, 2011October201118CEOS- 21, 2009SAR Calibration and Validation WorkshopProgress In ElectromagneticsFairbanks,ResearchAlaska, U.S.A.SymposiumPIERS 2009 in Moscow, RUSSIA, 18-21 August, 2009SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20111 of 27

Contents1. SAOCOM SAR Instrument Main Characteristics2. Calibration components3. External Calibration Model‣ Overview‣ TopSAR modes‣ Calibration sites4. Internal Calibration‣ Overview‣ Central Electronics Calibration - Scheme Fundamentals‣ Antenna Calibration5. SummarySAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20112 of 27

SAOCOM SAR InstrumentMAIN CHARACTERISTICS‣L-Band SAR‣ Right looking SAR‣ Left looking capability‣ 10m x 3.5m active phased arrayantenna with 140 TRMs‣ TOPSAR & STRIPMAPacquisition modes‣ Single, dual and quadpolarization operative modes‣More than 2600 beamsSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20113 of 27

SAOCOM Calibration ComponentsANTENNA MODELSAOCOMCALIBRATIONCOMPONENTSINTERNAL CALIBRATIONEXTERNAL CALIBRATIONSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20114 of 27

Antenna modelObjectivesAntenna beams shapeBeam to beam and pol to pol gainGS 1HHS 2HHS 3HHHigh number of beamsS 1VVS 2VVS 3VVDriversWorkflowRadiometric accuracy optimizationOn-Orbit calibration effort reductionPre-Launch extensive characterizationPre-Launch validation (near field/int. Cal pulses)On-Orbit verification & monitoring (rain forest)θBeamCoefficientsInt. CalTelemetrySAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20115 of 27

L2B Mission System Requirements Summary‣Antenna Pattern shall be verify from External Calibrationwith a precisión of 0.2 dB.‣Absolute calibration constant (K) shall be estimated fromExternal Calibration measurements with an uncertainty equalor less than 0.2dB.‣Crosstalk levels shall be estimated from External Calibrationmeasurements and and corrected so that the residual x-talksis less than -30dB‣Imbalance (f) shall be estimated with an uncertainty equal orless than 0.1dB.‣Image geolocation error in STRIPMAP mode shall be lessthan 2 resolution cells.SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20117 of 27

Beams designTo limit the calibration effort, all the modes are based on a totalset of 18 beams (in range):‣9 Quad-Pol‣9 Dual- Single PolTOPSAR mode waschosen to maximizecoverage vs geometricand radiometricresolution.SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20118 of 27

TOPSAR Absolute Calibration‣ Rely on the Antenna Model and the fact that the STRIPMAPbeams are used to construct the TOPSAR mode‣ Computation of absolute constant using corner reflectorfor STRIPMAP then conversion to TOPSAR modes‣ Verification using Corners reflector over very low backgroundSTRIPMAPTOPSAR WIntegration area [pixels] 20 x 20 20 x 20Corner RCS σ CR [dB] 38.1 38.1Background σ0B [dB] σ CR -15 -25Pixel area A [m²] 50 1000Confidence error [%] 95 95Salt Lakes for CRSingle Measurement error[dB]0.2 0.2712 Measurements error [dB] 0.05 0.08SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 20119 of 27

Calibration Sites for Corner Reflectors# AcquisitionsSQP-S1 60SQP-S2 6SQP-S3 16SQP-S4 7SQP-S5 6SQP-S6 15SQP-S7 6SQP-S8 22SQP-S9 4Total QP 142SDP-S1 38SDP-S2 9SDP-S3 21SDP-S4 50SDP-S5 30SDP-S6 72SDP-S7 60SDP-S8 0SDP-S9 36Total DP 316SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201110 of 27

Point Targets‣Some sites arealready operative forAirborne and satellitesuse.‣Mores sites areplanned in the nearfutureSARATCOSMOSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 2011ALOS11 of 27

L+X Malargue Calibration Site• 55 Km² area.• Background RCS of -10dB for X-bandand -15dB for L-band.• 1500 m height 2% of terrain slope.SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201112 of 27

L+X Malargue Calibration SiteTargets• 750 m away of any other object• 7 L band &12 X bandSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201113 of 27

Range Antenna Pattern Model Validation• Antenna pointing will be verified using a special “notch” beam (1).• A subset of beams will be validated: S1QP, S4QP, S8QP and S7DP (2).• The validity of the model will be assumed for the rest of the beams.• TOPSAR images correction will be verified as an end-to-end test (3).SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201114 of 27

Extended TargetsAmazon Rain ForestCongo Rain ForestSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201115 of 27

Azimuth antenna pattern and pointingSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201116 of 27

SAOCOM Calibration ComponentsANTENNA MODELSAOCOMCALIBRATIONCOMPONENTSINTERNAL CALIBRATIONEXTERNAL CALIBRATIONSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201117 of 27

SAOCOM Internal CalibrationNOISE ACQUISITIONS σ bias estimationCENTRAL ELECTRONICSCAL PULSESINTERNALCALIBRATIONCOMPONENTSANTENNACAL PULSESSensor driftsINSTRUMENT TELEMETRYON GROUNDCHARACTERIZATIONSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201118 of 27

Sensor Drifts• Review of the needs for measuring drifts• Sensor designed stable, however there will be drifts• ICAL compensates for these drifts => AccuracyParameter driftmeasured byICALSensorparameterParameter driftyFlight pathxSensorExternaltargetszSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201119 of 27

SAOCOM InstrumentCDUCRXDNHTRMTX HH PolSSG FERX HSSGCALNWV PolCEANTENNA (140 TRMs)SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201120 of 27

CE Calibration - Scheme Fundamentals (1/3)TX path / pulsesABK TXMagnitude drift:K(t=10 TX 1MDTX≡=KTX(t= t0)t)KK1TX0TXToCDUDownconverterFromcoreSSGX CRXb CRX←⎤ Γ CRXXb GSSGSS→⎤ Γ GSSQuadrature modulatorK TXCALNWK =TXXXCRX,BGSS,BXXGSS,ACRX,AFInput and outputsignals from cal pulsesPaths in pulses A and Band nominal elementsTX21 of 27

CE Calibration - Scheme Fundamentals (2/3)Scheme PerformanceActual:Without considering F TX :10TXKTXMD = =K10TXXXXX1CRX,B10GSS,BCRX,B0GSS,BXXXX110GSS,ACRX,A0GSS,ACRX,AFF1TX0TXEMD =10TXXXXX1CRX,B10GSS,BCRX,B0GSS,BXXXX11CRX,A00GSS,AGSS,ACRX,AεMD10TX≡EMD10TX/ MD10TX=11+ ∆F10TX/ F0TXPerformance depends on the relative change of F TX : ∆F10TX=F1TX− F0TXSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201122 of 27

CE Calibration - Scheme Fundamentals (3/3)• Scattering parameters• Partial increments⎡A⎢⎢⎣A1112AA2122⎤⎥⎥⎦∆F/ F ≅∑i∂F∆v∂vii/ FTwo type of uncertainty sources:∆A21 / A 21− ∆B21 / B 21( 1+C21·C32·Γ2/ C31) · C21/ C211/∆( C22 − C21·C32/ C31) · ∆Γ2222+ A22+ A21· ΓGSS)( −B∆Γ211+ A21· ΓCRX)( A∆Γ: :GSSCRX• AS A RESULT:Instabilities of theICAL NW– We obtain the ICAL performance in terms of measurable parameters– We understand the influence of each parameter on the total uncertainty– We can derive guidelines for ICAL NW designChanges innominal HWSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201123 of 27

Antenna Calibration• Similar concept as for calibration of the CE• In-flight measurements of TRMs (PCC)• Models of passive devices (AM)TRM Transmission ChainTRM Reception ChainSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201124 of 27

Summary (1/2)1. The SAOCOM calibration Strategy is build upon three features:Antenna Model, External Calibration and InternalCalibration.2. TOPSAR mode absolute Calibration made use of theAntenna model and the STRIPMAP Calibration with CR s.3. Many Calibration sites are planned or underway in Argentinafor Corner Reflector and use of both Amazon and CongoForest is envisaged as extended targets4. Ground receptors are foreseen to be used for both validationof some azimuth beams and pointing.SAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201125 of 27

Summary (2/2)5. The SAOCOM ICAL Strategy was presented focusing onmeasurement accuracy, together with a proposed method forestimating the ICAL performance6. The method can be used to drive the ICAL network design,including requirements allocation to its components7. Potential error sources such as the effect of changes in thereflection coefficients of nominal elements were considered8. The method is planned to be used for the final version of the ICALnetworkSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201126 of 27

Thank YouSAOCOM Calibration StrategyM. Azcueta, J. Giardini, J. P. Cuesta González, M. Thibeault, T. ZajcCEOS 2011 Workshop, Fairbanks, Alaska, U.S.A., November 7-9, 201127 of 27

Back-Up Slides - CE Transmission GainCRX3To CDUFromcore GSSXCRX,ADownconverterXGSS,AQuadraturemodulatorbCRX,A ←⎤ ΓCRXCRX RF Input SectionbGSS,A →⎤ ΓGSS2GSS1CRX RF SW21123ACTXTRRS3DC212CALNWGSS RF Output SectionGSS RF SWFigure 1. Calibration pulse A.CRX3To CDUFromcore GSSXCRX,BDownconverterXGSS,BQuadraturemodulatorbCRX,B←⎤ ΓCRXCRX RF Input SectionbGSS,B→⎤ ΓGSS2GSSCRX RF SW21123CTXTRRSDC2 C1 231D32 1CALNWBGSS RF Output SectionGSS RF SWFigure 2. Calibration pulse B.CRX3To CDUFromcore GSSXCRXDownconverterXGSSQuadraturemodulatorbCRX←⎤ ΓCRXCRX RF Input SectionbGSS→⎤ ΓGSSGSSCRX RF SW21123CTXTRRSEGDC21 231F32CALNWGSS RF Output SectionGSS RF SW28 of 27

Back-Up Slides - All PulsesABCCE Transmission ChainCE Reception ChainTRM Transmission ChainTRM Reception Chain29 of 27