TU2.L09.1	 - COMPACT POLARIMETRY AT THE MOON: THE MINI-RF RADARS
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TU2.L09.1 - COMPACT POLARIMETRY AT THE MOON: THE MINI-RF RADARS

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    TU2.L09.1	 - COMPACT POLARIMETRY AT THE MOON: THE MINI-RF RADARS TU2.L09.1 - COMPACT POLARIMETRY AT THE MOON: THE MINI-RF RADARS Presentation Transcript

    • Compact Polarimetry at the Moon: The Mini-RF Radars R. Keith Raney1, Paul Spudis2, Ben Bussey1, J. Robert Jensen1, Bill Marinelli3, Priscilla McKerracher1, Ron Schulze1, Herman Sequeira1, and Helene Winters1 1JHU/APL 2LPI/TX 3NASA/Hdqs IGARSS, Honolulu, HI 25 - 30 July 2010
    • Outline Mini-RF Project Overview Mini-RF Project Overview Hybrid Polarimetric Architecture Hybrid Polarimetric Architecture Calibration Calibration Results Results Conclusions Conclusions R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini-RF Project Overview Mini-RF Project Overview Hybrid Polarimetric Architecture Hybrid Polarimetric Architecture Calibration Calibration Results Results Conclusions Conclusions R. K. Raney IGARSS 2010, Honolulu, HI
    • Top-Level Parameters of the Mini-RF radars Chandrayaan-1 Chandrayaan-1 LRO LRO (2008 – 2009) (2008 – 2009) (2009 -- )) (2009 Polarizations Polarizations Tx C; Rx L (H&V) Tx C; Rx L (H&V) Tx C; Rx L (H&V) Tx C; Rx L (H&V) Resolution (m) //Looks Resolution (m) Looks 150 //16 150 16 Baseline Baseline 150 //16 150 16 Zoom Zoom 15 x 30 //8 15 x 30 8 Wavelengths (cm) Wavelengths (cm) 12.6 12.6 12.6, 4.2 12.6, 4.2 Modes Modes Strip Strip Strip, InSAR Strip, InSAR Altitude (km) Altitude (km) 100 100 50 50 Inclination Inclination ~ Polar ~ Polar ~ Polar ~ Polar Mass (kg) Mass (kg) 12 12 15 15 R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini-RF Radar on LRO H H H Antenna Interconnect Analog Receiver Digital Receiver • Tx and Rx S/C Module • Digitize IF signals • Down-convert band signals • Perform BAQ • Generate 90 deg. from RF to IF • Transmit CP V V V • Generate digital I/Q Phase shift on • Provide gain • Receive V&H • CCSDS packetize V&H Tx channels control • Isolate transmit & receive paths QDWS Analog Exciter • Filter RF • Provide LOs & clocks • Timing & control • Up-convert: S to C • Generate radar waveforms Bus Electronics Transmitter LO & Clock Timing Signals (HK/IO) • Amplify S/C band signals Controls Telemetry Control Processor (RAD 750) • Digitize antenna temperatures • Collect & report telemetry to bus electronics • Accept commands from bus electronics • Control & configure payload electronics • Provide router interface from digital receiver to bus electronics for radar data R. K. Raney IGARSS 2010, Honolulu, HI
    • Technology Demo (LRO): Microwave Power Module Conventional TWTA (40 W) MPM (100 W) MPM TWT R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini-RF Radar on LRO During Integration and Test Solar panel array (folded) Mini-RF antenna (~ 1 m2 area) R. K. Raney IGARSS 2010, Honolulu, HI
    • Water-Ice – Relatively large CPR* Mercury’s poles: Mercury’s poles: Arecibo S-band, Arecibo S-band, delay-Doppler delay-Doppler processing-- processing-- enhanced “same- enhanced “same- sense” (SC) circular sense” (SC) circular polarization, which polarization, which is usually the is usually the weaker return for weaker return for 85 circular-polarization circular-polarization on transmission on transmission 80 *COBE: Coherent Opposition Harmon et al., 2000 Backscatter Effect From Ostro, 2000 R. K. Raney IGARSS 2010, Honolulu, HI
    • Dominant Requirements on the Mini-RF Radars Measure circular polarization ratio (CPR) Measure circular polarization ratio (CPR) •• Consequence: radar must transmit Circular Polarization Consequence: radar must transmit Circular Polarization Maximal science with minimal flight hardware Maximal science with minimal flight hardware R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini_RF Project Overview Mini_RF Project Overview Hybrid Polarimetric Architecture Hybrid Polarimetric Architecture Calibration Calibration Results Results Conclusions Conclusions R. K. Raney IGARSS 2010, Honolulu, HI
    • Hierarchy of Polarimetric Imaging Radars Radar Processing Result Nomenclature No assumptions 4x4 scattering matrix Full polarization Orthogonal Tx pols Coherent Dual Rx Reciprocity & 3x3 scattering Quadrature symmetry matrix polarization Symmetry 3x3 pseudo- One Tx Pol, assumptions scattering matrix Compact Coherent Dual Rx No symmetry 2x2 covariance polarization assumptions matrix 2 magnitudes 2 orthogonal Like- & co-pol phase pol images & CPD Two Tx pols 2 orthogonal 2 magnitudes Dual Like-pol images polarization Like- and Cross- Two Rx pols 2 magnitudes pol images One Magnitude Mono- Real image polarization polarization R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini-RF: Compact Polarimetric Radars Radar Processing Result Nomenclature No assumptions 4x4 scattering matrix Full polarization Orthogonal Tx pols Coherent Dual Rx Reciprocity & 3x3 scattering Quadrature symmetry matrix polarization Symmetry 3x3 pseudo- One Tx Pol, assumptions scattering matrix Compact Coherent Dual Rx No symmetry 2x2 covariance polarization assumptions matrix 2 magnitudes 2 orthogonal Like- & co-pol phase pol images & CPD Two Tx pols 2 orthogonal 2 magnitudes Dual Like-pol images polarization Like- and Cross- Two Rx pols 2 magnitudes pol images One Magnitude Mono- Real image polarization polarization R. K. Raney IGARSS 2010, Honolulu, HI
    • Hybrid-Polarity Radar Architecture* Transmit circular; Receive orthogonal linears and relative phase Covariance matrix => 4 Stokes Covariance matrix => 4 Stokes Transmitter & 90o waveform parameters => independent of parameters => independent of polarization basis => optimize polarization basis => optimize radar hardware => Linear pol radar hardware => Linear pol Timing & control V H receiver => Hybrid Polarity receiver => Hybrid Polarity |H|2 S1 H H Rx channel LNA L-0 L-1 S2 X H HV* S3 V V* S4 LNA V Rx channel L-0 L-1 |V|2 V H Antenna Part of the Radar Processing Transmits Facility in the ground-based circular operations center polarization V H * U. S. Patent # 7,746,267 R. K. Raney IGARSS 2010, Honolulu, HI
    • Stokes Parameters Linear basis Circular basis Poincaré basis S1 = < |EH|2 + |EV |2 > + N0 = < |ER|2 + |EL|2 > + N0 = S1 S2 = < |EH|2 – |EV|2 > = 2 Re < EREL* > = m S1 cos 2ψ cos 2χ S3 = 2 Re < EHEV*> = 2 Im < EREL* > = m S1 sin 2ψ cos 2χ S4 = – 2 Im < EHEV*> = – < |ER|2 – |EL|2 > = – m S1 sin 2χ Comments > Assumes that LCP is transmitted (or a close approximation there to) > Note that the radar’s additive noise N0 is included in S1 (correctly), but not in the other Stokes parameters (also correctly) SNR = < |EH|2 + |EV |2 > / N0 > The child parameters may be found by taking advantage of the equality of the Stokes parameters across all bases of observation of the received EM field > The sign of S4 is negative, consistent with the back-scattering alignment (BSA) convention R. K. Raney IGARSS 2010, Honolulu, HI
    • Stokes Parameters are Independent of Receive Polarization Basis Stokes 1 Stokes 2 Stokes parameters Stokes parameters derived from Log CC derived from Log CC airborne SAR data airborne SAR data for circularly for circularly polarized polarized transmissions and transmissions and Log CL Log CL dual linear or dual dual linear or dual circular received circular received Stokes 3 Stokes 4 polarizations are polarizations are Log CC Log CC essentially identical essentially identical Log CL Log CL R. K. Raney IGARSS 2010, Honolulu, HI
    • Stokes Child Parameters Degree of polarization Comments m = (S22 + S32 + S42)½ / S1 > Assumes that LCP is Degree of depolarization mD = 1 – m transmitted (or a close approximation there to) Degree of circular polarization mC = – S4 / mS1 = sin 2χ > Note that the degree of linear polarization and degree of Degree of linear polarization circular polarization include mL = (S22 + S32)½ / mS1 = cos 2χ the degree of polarization m Degree of ellipticity > The sign of S4 depends on the mE = tan χ handedness of the transmitted Circular polarization ratio circular polarization (and the µC = (S1 – S4) / (S1 + S4) coordinate convention, BSA vs FSA) Linear polarization ratio µL = (S1 – S2) / (S1 + S2) > Notice the minus sign on the S4 terms (mC , CPR, & δ) Relative phase δ = arctan (– S4 / S3 ) R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini_RF Project Overview Mini_RF Project Overview Hybrid Polarimetric Architecture Hybrid Polarimetric Architecture Calibration Calibration Results Results Conclusions Conclusions R. K. Raney IGARSS 2010, Honolulu, HI
    • Relative Self Calibration h H | |2 |H|2 Tx Rx v P X HV* V | |2 |V|2 Raw signal Image domain ( domain (before calibration) Nadir-viewing Method*: <[Nadir returns]> => opposite sense of CP; Method*: <[Nadir returns]> => opposite sense of CP; V/H magnitude imbalance; V-H phase difference => V/H magnitude imbalance; V-H phase difference => calibration coefficients Cδδand Cφ calibration coefficients C and Cφ If transmitted 1/Cδ field is not near- perfect circular h | |2 X |HC|2 polarization, H P X Cφ HVC* then external v V | |2 X |VC|2 resources are Raw signal Image domain needed domain (after Cδ calibration) (GBT, ART) R. K. Raney IGARSS 2010, Honolulu, HI
    • CPR is Robust with Non-unity Transmit Axial Ratio CPR = f(axial ratio, degree of polarization) Notes > CPR evaluated under the 1.50 assumption of SC backscatter in 1.45 response to LC transmission, hence 1.40 - 45o ≤ χ ≤ 0 m’ = 0.8 1.35 m’ = 0.7 CPR 1.30 1fffffffff2χf @ m. αsin ff ffffffffffff fffffffffff m’ = 0.6 µC = 1.25 1 + m. αsin 2χ m’ = 0.5 1.20 > Smaller signal-to-noise ratio 1.15 (larger NES0) has the same effect 1.10 as smaller degree of polarization 1 1.2 1.4 1.6 1.8 2 m: Transm it Axial Ratio ~2.4 dB m’ = m/(1 + 1/SNR) > α accounts for imperfect dielectric and geometric properties of the source backscatter, which when evaluated from Mini-RF data has a nominal value of about 0.19 R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini_RF Project Overview Mini_RF Project Overview Hybrid Polarimetric Architecture Hybrid Polarimetric Architecture Calibration Calibration Results Results Conclusions Conclusions R. K. Raney IGARSS 2010, Honolulu, HI
    • Linne Crater seen in Total Power (S1) and Circular Polarization Ratio (CPR) Radar look aspect R. K. Raney IGARSS 2010, Honolulu, HI
    • Crater Floor-Wall Image Characteristic Direct path (rim image) Image location of floor-wall backscatter nge Rim Floor-far-wall a ra E xtr Far-side exterior double bounce ~ Floor R. K. Raney IGARSS 2010, Honolulu, HI
    • CL-Pol Decomposition: m-δ color code The decomposition colorization scheme is: S1 = R2 + G2 + B2 R = [S1m (1 + sin δ)/2]1/2 G = [S1 (1 – m)]1/2 B = [S1m (1 - sin δ)/2]1/2 S1 first Stokes parameter (total power) m degree of polarization δ relative H/V phase (e.g., ellipticity) R (Red) double bounce backscatter (e.g., dihedral, volume ice) G (Green) randomly polarized (e.g., volume scattering) B (Blue) odd bounce backscatter (e.g., Bragg scattering) R. K. Raney IGARSS 2010, Honolulu, HI
    • Radar look aspect Example of m-delta Decomposition Anomalous odd-bounce and even-bounce (or COBE?) floor-wall signatures from the same crater R. K. Raney IGARSS 2010, Honolulu, HI
    • SC CPR North polar mosaic Rozhdestvensky (177 kilometers in diameter) (S-band Zoom mode) CPR rendition (Late June 2010) Processing, Courtesy of Catherine Neish, APL R. K. Raney IGARSS 2010, Honolulu, HI
    • SC Interesting crater in the floor of Rozhdestvensky… R. K. Raney IGARSS 2010, Honolulu, HI
    • SC Permanent sun shadow Calculate the CPR Not histograms of permanent shadowed vs non- sun shadow shadowed backscatter SC background for reference R. K. Raney IGARSS 2010, Honolulu, HI
    • CPR Signature is Consistent CPR Signature is Consistent with Water-Ice Deposition with Water-Ice Deposition Inside the Crater Inside the Crater Permanent sun shadow Not permanent sun shadow R. K. Raney IGARSS 2010, Honolulu, HI
    • Mini_RF Project Overview Mini_RF Project Overview Hybrid Polarimetric Architecture Hybrid Polarimetric Architecture Calibration Calibration Results Results Conclusions Conclusions R. K. Raney IGARSS 2010, Honolulu, HI
    • Conclusions The Mini-RF radars are the first polarimetric imagers The Mini-RF radars are the first polarimetric imagers outside of Earth orbit outside of Earth orbit Hybrid-Polarity (Tx Circular, Rx dual coherent linear Hybrid-Polarity (Tx Circular, Rx dual coherent linear polarizations) is an ideal compact polarimeter for lunar or polarizations) is an ideal compact polarimeter for lunar or planetary exploration: maximum science and minimal hdw planetary exploration: maximum science and minimal hdw In the lunar application, CPR interpretations are robust In the lunar application, CPR interpretations are robust in response to imperfect circular transmit polarization in response to imperfect circular transmit polarization Calibration techniques unique to and pioneered by the Calibration techniques unique to and pioneered by the Mini-RF radars have proven to be effective Mini-RF radars have proven to be effective Lunar imagery and interpreted products are as expected Lunar imagery and interpreted products are as expected R. K. Raney IGARSS 2010, Honolulu, HI