tu2.l09.1 - compact polarimetry at the moon: the mini-rf radars
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
R. K. Raney IGARSS 2010, Honolulu, HI
Outline
� Mini-RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
� Mini-RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
R. K. Raney IGARSS 2010, Honolulu, HI
� Mini-RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
� Mini-RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
R. K. Raney IGARSS 2010, Honolulu, HI
Top-Level Parameters of the Mini-RF radars
Chandrayaan-1 LRO
(2008 – 2009) (2009 - )
� Polarizations Tx C; Rx L (H&V) Tx C; Rx L (H&V)
� Resolution (m) / Looks 150 / 16 Baseline 150 / 16
Zoom 15 x 30 / 8
� Wavelengths (cm) 12.6 12.6, 4.2
� Modes Strip Strip, InSAR
� Altitude (km) 100 50
� Inclination ~ Polar ~ Polar
� Mass (kg) 12 15
Chandrayaan-1 LRO
(2008 – 2009) (2009 - )
� Polarizations Tx C; Rx L (H&V) Tx C; Rx L (H&V)
� Resolution (m) / Looks 150 / 16 Baseline 150 / 16
Zoom 15 x 30 / 8
� Wavelengths (cm) 12.6 12.6, 4.2
� Modes Strip Strip, InSAR
� Altitude (km) 100 50
� Inclination ~ Polar ~ Polar
� Mass (kg) 12 15
R. K. Raney IGARSS 2010, Honolulu, HI
Antenna
• Tx and Rx S/C
band signals
• Transmit CP
• Receive V&H
InterconnectModule
• Generate 90 deg.
Phase shift on
V&H Tx channels
• Isolate transmit &
receive paths
• Filter RF
Digital Receiver
• Digitize IF signals
• Perform BAQ
• Generate digital I/Q
• CCSDS packetize
QDWS• Timing & control
• Generate radar
waveforms
Transmitter
• Amplify S/C band
signals
Analog Receiver
Analog Exciter
• Provide LOs & clocks
• Up-convert: S to C
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
Bus Electronics
(HK/IO)
Controls
Timing SignalsLO & Clock
Telemetry
H
V
H
V
H
V
• Down-convert
from RF to IF
• Provide gain
control
Mini-RF Radar on LRO
R. K. Raney IGARSS 2010, Honolulu, HI
Conventional TWTA (40 W)
MPM (100 W)
MPM TWT
Technology Demo (LRO): Microwave Power Module
R. K. Raney IGARSS 2010, Honolulu, HI
Solar panel
array (folded)
Mini-RF antenna
(~ 1 m2 area)
Mini-RF Radar on LRO During Integration and Test
R. K. Raney IGARSS 2010, Honolulu, HI
85
80
Water-Ice – Relatively large CPR*
Harmon et al., 2000
Mercury’s poles:
Arecibo S-band,
delay-Doppler
processing--
enhanced “same-
sense” (SC) circular
polarization, which
is usually the
weaker return for
circular-polarization
on transmission
Mercury’s poles:
Arecibo S-band,
delay-Doppler
processing--
enhanced “same-
sense” (SC) circular
polarization, which
is usually the
weaker return for
circular-polarization
on transmission
From Ostro, 2000
*COBE: Coherent
Opposition
Backscatter Effect
R. K. Raney IGARSS 2010, Honolulu, HI
Dominant Requirements on the Mini-RF Radars
� Measure circular polarization ratio (CPR)
• Consequence: radar must transmit Circular Polarization
� Maximal science with minimal flight hardware
� Measure circular polarization ratio (CPR)
• Consequence: radar must transmit Circular Polarization
� Maximal science with minimal flight hardware
R. K. Raney IGARSS 2010, Honolulu, HI
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
R. K. Raney IGARSS 2010, Honolulu, HI
Radar Result
Orthogonal Tx polsCoherent Dual Rx
One Tx Pol, Coherent Dual Rx
One polarization
Processing Nomenclature
Real image
No assumptions
Reciprocity & symmetry
4x4 scattering matrix
3x3 scattering matrix
Symmetry assumptions
No symmetry assumptions
3x3 pseudo-scattering matrix
2x2 covariance matrix
Full polarization
Quadrature
polarization
Compact
polarization
Two Rx pols
Two Tx pols
Magnitude
2 magnitudes & co-pol phase
2 magnitudes
2 magnitudes
Like- and Cross-pol images
2 orthogonal Like-pol images
2 orthogonal Like-pol images & CPD
Dual
polarization
Mono-
polarization
Radar Result
Orthogonal Tx polsCoherent Dual Rx
Orthogonal Tx polsCoherent Dual Rx
One Tx Pol, Coherent Dual Rx
One Tx Pol, Coherent Dual Rx
One polarization
One polarization
Processing Nomenclature
Real image
No assumptions
Reciprocity & symmetry
4x4 scattering matrix
3x3 scattering matrix
Symmetry assumptions
Symmetry assumptions
No symmetry assumptionsNo symmetry assumptions
3x3 pseudo-scattering matrix
2x2 covariance matrix
3x3 pseudo-scattering matrix
2x2 covariance matrix
Full polarization
Quadrature
polarization
Compact
polarization
Two Rx polsTwo Rx pols
Two Tx polsTwo Tx pols
Magnitude Magnitude
2 magnitudes & co-pol phase2 magnitudes
& co-pol phase
2 magnitudes2 magnitudes
2 magnitudes2 magnitudes
Like- and Cross-pol images
2 orthogonal Like-pol images
2 orthogonal Like-pol images & CPD
Dual
polarization
Mono-
polarization
Hierarchy of Polarimetric Imaging Radars
R. K. Raney IGARSS 2010, Honolulu, HI
Radar Result
Orthogonal Tx polsCoherent Dual Rx
One Tx Pol, Coherent Dual Rx
One polarization
Processing Nomenclature
Real image
No assumptions
Reciprocity & symmetry
4x4 scattering matrix
3x3 scattering matrix
Symmetry assumptions
No symmetry assumptions
3x3 pseudo-scattering matrix
2x2 covariance matrix
Full polarization
Quadrature
polarization
Compact
polarization
Two Rx pols
Two Tx pols
Magnitude
2 magnitudes & co-pol phase
2 magnitudes
2 magnitudes
Like- and Cross-pol images
2 orthogonal Like-pol images
2 orthogonal Like-pol images & CPD
Dual
polarization
Mono-
polarization
Radar Result
Orthogonal Tx polsCoherent Dual Rx
Orthogonal Tx polsCoherent Dual Rx
One Tx Pol, Coherent Dual Rx
One Tx Pol, Coherent Dual Rx
One polarization
One polarization
Processing Nomenclature
Real image
No assumptions
Reciprocity & symmetry
4x4 scattering matrix
3x3 scattering matrix
Symmetry assumptions
Symmetry assumptions
No symmetry assumptionsNo symmetry assumptions
3x3 pseudo-scattering matrix
2x2 covariance matrix
3x3 pseudo-scattering matrix
2x2 covariance matrix
Full polarization
Quadrature
polarization
Compact
polarization
Two Rx polsTwo Rx pols
Two Tx polsTwo Tx pols
Magnitude Magnitude
2 magnitudes & co-pol phase2 magnitudes
& co-pol phase
2 magnitudes2 magnitudes
2 magnitudes2 magnitudes
Like- and Cross-pol images
2 orthogonal Like-pol images
2 orthogonal Like-pol images & CPD
Dual
polarization
Mono-
polarization
Mini-RF: Compact Polarimetric Radars
R. K. Raney IGARSS 2010, Honolulu, HI
Hybrid-Polarity Radar Architecture*
Transmit circular; Receive orthogonal linears and relative phase
Transmitter &
waveform
Antenna
H Rx channel
V Rx channel
90o
H
V
V
H
LNA
LNA
Timing & control
L-1
L-0
L-0
L-1
Part of the Radar Processing
Facility in the ground-based
operations center
V H
V H
|H|2
|V|2
HV*H
V*XXXX
S1
S2
S3
S4
Covariance matrix => 4 Stokes
parameters => independent of
polarization basis => optimize
radar hardware => Linear pol
receiver => Hybrid Polarity
Covariance matrix => 4 Stokes
parameters => independent of
polarization basis => optimize
radar hardware => Linear pol
receiver => Hybrid Polarity
Transmits circular
polarization
* 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 1 Stokes 2
Stokes 3Stokes 4
Log CL
Log CLLog CL
Log CL
Log C
CLog C
C
Log C
CLog C
C
Stokes Parameters are Independent
of Receive Polarization Basis
Stokes parameters
derived from
airborne SAR data
for circularly
polarized
transmissions and
dual linear or dual
circular received
polarizations are
essentially identical
Stokes parameters
derived from
airborne SAR data
for circularly
polarized
transmissions and
dual linear or dual
circular received
polarizations are
essentially identical
R. K. Raney IGARSS 2010, Honolulu, HI
Stokes Child Parameters
Degree of polarization
m = (S22 + S3
2 + S42)½ / S1
Degree of linear polarization
mL = (S22 + S3
2)½ / mS1 = cos 2χ
Degree of circular polarization
mC = – S4 / mS1 = sin 2χ
Circular polarization ratio
µC = (S1 – S4) / (S1 + S4)
Linear polarization ratio
µL = (S1 – S2) / (S1 + S2)
Degree of depolarization mD = 1 – m
Relative phase δ = arctan (– S4 / S3 )
Degree of ellipticity
mE = tan χ
Comments
> Note that the degree of linear
polarization and degree of
circular polarization include
the degree of polarization m
> The sign of S4 depends on the
handedness of the transmitted
circular polarization (and the
coordinate convention, BSA vs
FSA)
> Assumes that LCP is
transmitted (or a close
approximation there to)
> Notice the minus sign on
the S4 terms (mC , CPR, & δ)
R. K. Raney IGARSS 2010, Honolulu, HI
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
R. K. Raney IGARSS 2010, Honolulu, HI
(
Nadir-viewing
Tx Rx PH
VHV*|H|2
|V|2
Raw signal domain
Image domain(before
calibration)
v
h
X| |2
| |2
Relative Self Calibration
PH
VHVC*
|HC|2
|VC|2
Raw signal domain
Image domain(after
calibration)
v
h
X
| |2
| |2
X
X
Cδ
1/Cδ
Cφ
Method*: <[Nadir returns]> => opposite sense of CP;
V/H magnitude imbalance; V-H phase difference =>
calibration coefficients Cδ
and Cφ
Method*: <[Nadir returns]> => opposite sense of CP;
V/H magnitude imbalance; V-H phase difference =>
calibration coefficients Cδ
and CφIf transmitted
field is not near-
perfect circular
polarization,
then external
resources are
needed
(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)
1.10
1.15
1.20
1.25
1.30
1.35
1.40
1.45
1.50
1 1.2 1.4 1.6 1.8 2
Transmit Axial Ratio
CP
R
m’ = 0.8
m’ = 0.7
m’ = 0.5
m’ = 0.6
~2.4 dB
Notes
µC
=1@m. αsin 2χ
1 + m. αsin 2χ
fffffffffffffffffffffffffffffffffff
> Smaller signal-to-noise ratio
(larger NES0) has the same effect
as smaller degree of polarization
m:
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
> CPR evaluated under the
assumption of SC backscatter in
response to LC transmission, hence
- 45o ≤ χ ≤ 0
R. K. Raney IGARSS 2010, Honolulu, HI
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
R. K. Raney IGARSS 2010, Honolulu, HI
Radar
look
aspect
Linne Crater seen in Total Power
(S1) and Circular Polarization
Ratio (CPR)
R. K. Raney IGARSS 2010, Honolulu, HI
Floor
Rim
Far-side exterior
Direct path
(rim image)
Floor-far-wall
double bounce ~ Extra
range
Image
location of
floor-wall
backscatter
Crater Floor-Wall Image Characteristic
R. K. Raney IGARSS 2010, Honolulu, HI
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 δδδδ)/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)
CL-Pol Decomposition: m-δ color code
R. K. Raney IGARSS 2010, Honolulu, HI
Example of m-delta DecompositionAnomalous odd-bounce and even-bounce (or
COBE?) floor-wall signatures from the same crater
Radar look
aspect
R. K. Raney IGARSS 2010, Honolulu, HI
Rozhdestvensky(177 kilometers in diameter)
North polar mosaic
(S-band Zoom
mode) CPR
rendition
(Late June 2010)
Processing, Courtesy of
Catherine Neish, APL
CPRSC
R. K. Raney IGARSS 2010, Honolulu, HI
Interesting crater in
the floor of
Rozhdestvensky…
SC
R. K. Raney IGARSS 2010, Honolulu, HI
Permanent sun shadow
Not
permanent sun shadow
Calculate the CPR histograms of
shadowed vs non-shadowed
backscatter
SC background for reference
SC
R. K. Raney IGARSS 2010, Honolulu, HI
Permanent sun shadow
Not
permanent sun shadow
CPR Signature is Consistent
with Water-Ice Deposition
Inside the Crater
CPR Signature is Consistent
with Water-Ice Deposition
Inside the Crater
R. K. Raney IGARSS 2010, Honolulu, HI
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
� Mini_RF Project Overview
� Hybrid Polarimetric Architecture
� Calibration
� Results
� Conclusions
R. K. Raney IGARSS 2010, Honolulu, HI
Conclusions
� The Mini-RF radars are the first polarimetric imagers
outside of Earth orbit
� Hybrid-Polarity (Tx Circular, Rx dual coherent linear
polarizations) is an ideal compact polarimeter for lunar or
planetary exploration: maximum science and minimal hdw
� In the lunar application, CPR interpretations are robust
in response to imperfect circular transmit polarization
� Calibration techniques unique to and pioneered by the
Mini-RF radars have proven to be effective
� Lunar imagery and interpreted products are as expected
� The Mini-RF radars are the first polarimetric imagers
outside of Earth orbit
� Hybrid-Polarity (Tx Circular, Rx dual coherent linear
polarizations) is an ideal compact polarimeter for lunar or
planetary exploration: maximum science and minimal hdw
� In the lunar application, CPR interpretations are robust
in response to imperfect circular transmit polarization
� Calibration techniques unique to and pioneered by the
Mini-RF radars have proven to be effective
� Lunar imagery and interpreted products are as expected